MILLER(1)							     MILLER(1)



NAME
       Miller is like awk, sed, cut, join, and sort for name-indexed data such
       as CSV and tabular JSON.

SYNOPSIS
       Usage: mlr [I/O options] {verb} [verb-dependent options ...] {zero or
       more file names}


DESCRIPTION
       Miller operates on key-value-pair data while the familiar Unix tools
       operate on integer-indexed fields: if the natural data structure for
       the latter is the array, then Miller's natural data structure is the
       insertion-ordered hash map.  This encompasses a variety of data
       formats, including but not limited to the familiar CSV, TSV, and JSON.
       (Miller can handle positionally-indexed data as a special case.) This
       manpage documents Miller v5.3.0.

EXAMPLES
   COMMAND-LINE SYNTAX
       mlr --csv cut -f hostname,uptime mydata.csv
       mlr --tsv --rs lf filter '$status != "down" && $upsec >= 10000' *.tsv
       mlr --nidx put '$sum = $7 < 0.0 ? 3.5 : $7 + 2.1*$8' *.dat
       grep -v '^#' /etc/group | mlr --ifs : --nidx --opprint label group,pass,gid,member then sort -f group
       mlr join -j account_id -f accounts.dat then group-by account_name balances.dat
       mlr --json put '$attr = sub($attr, "([0-9]+)_([0-9]+)_.*", "\1:\2")' data/*.json
       mlr stats1 -a min,mean,max,p10,p50,p90 -f flag,u,v data/*
       mlr stats2 -a linreg-pca -f u,v -g shape data/*
       mlr put -q '@sum[$a][$b] += $x; end {emit @sum, "a", "b"}' data/*
       mlr --from estimates.tbl put '
	 for (k,v in $*) {
	   if (is_numeric(v) && k =~ "^[t-z].*$") {
	     $sum += v; $count += 1
	   }
	 }
	 $mean = $sum / $count # no assignment if count unset'
       mlr --from infile.dat put -f analyze.mlr
       mlr --from infile.dat put 'tee > "./taps/data-".$a."-".$b, $*'
       mlr --from infile.dat put 'tee | "gzip > ./taps/data-".$a."-".$b.".gz", $*'
       mlr --from infile.dat put -q '@v=$*; dump | "jq .[]"'
       mlr --from infile.dat put  '(NR % 1000 == 0) { print > stderr, "Checkpoint ".NR}'

   DATA FORMATS
	 DKVP: delimited key-value pairs (Miller default format)
	 +---------------------+
	 | apple=1,bat=2,cog=3 | Record 1: "apple" => "1", "bat" => "2", "cog" => "3"
	 | dish=7,egg=8,flint  | Record 2: "dish" => "7", "egg" => "8", "3" => "flint"
	 +---------------------+

	 NIDX: implicitly numerically indexed (Unix-toolkit style)
	 +---------------------+
	 | the quick brown     | Record 1: "1" => "the", "2" => "quick", "3" => "brown"
	 | fox jumped	       | Record 2: "1" => "fox", "2" => "jumped"
	 +---------------------+

	 CSV/CSV-lite: comma-separated values with separate header line
	 +---------------------+
	 | apple,bat,cog       |
	 | 1,2,3	       | Record 1: "apple => "1", "bat" => "2", "cog" => "3"
	 | 4,5,6	       | Record 2: "apple" => "4", "bat" => "5", "cog" => "6"
	 +---------------------+

	 Tabular JSON: nested objects are supported, although arrays within them are not:
	 +---------------------+
	 | {		       |
	 |  "apple": 1,        | Record 1: "apple" => "1", "bat" => "2", "cog" => "3"
	 |  "bat": 2,	       |
	 |  "cog": 3	       |
	 | }		       |
	 | {		       |
	 |   "dish": {	       | Record 2: "dish:egg" => "7", "dish:flint" => "8", "garlic" => ""
	 |     "egg": 7,       |
	 |     "flint": 8      |
	 |   }, 	       |
	 |   "garlic": ""      |
	 | }		       |
	 +---------------------+

	 PPRINT: pretty-printed tabular
	 +---------------------+
	 | apple bat cog       |
	 | 1	 2   3	       | Record 1: "apple => "1", "bat" => "2", "cog" => "3"
	 | 4	 5   6	       | Record 2: "apple" => "4", "bat" => "5", "cog" => "6"
	 +---------------------+

	 XTAB: pretty-printed transposed tabular
	 +---------------------+
	 | apple 1	       | Record 1: "apple" => "1", "bat" => "2", "cog" => "3"
	 | bat	 2	       |
	 | cog	 3	       |
	 |		       |
	 | dish 7	       | Record 2: "dish" => "7", "egg" => "8"
	 | egg	8	       |
	 +---------------------+

	 Markdown tabular (supported for output only):
	 +-----------------------+
	 | | apple | bat | cog | |
	 | | ---   | --- | --- | |
	 | | 1	   | 2	 | 3   | | Record 1: "apple => "1", "bat" => "2", "cog" => "3"
	 | | 4	   | 5	 | 6   | | Record 2: "apple" => "4", "bat" => "5", "cog" => "6"
	 +-----------------------+

OPTIONS
       In the following option flags, the version with "i" designates the
       input stream, "o" the output stream, and the version without prefix
       sets the option for both input and output stream. For example: --irs
       sets the input record separator, --ors the output record separator, and
       --rs sets both the input and output separator to the given value.

   HELP OPTIONS
	 -h or --help		      Show this message.
	 --version		      Show the software version.
	 {verb name} --help	      Show verb-specific help.
	 --help-all-verbs	      Show help on all verbs.
	 -l or --list-all-verbs       List only verb names.
	 -L			      List only verb names, one per line.
	 -f or --help-all-functions   Show help on all built-in functions.
	 -F			      Show a bare listing of built-in functions by name.
	 -k or --help-all-keywords    Show help on all keywords.
	 -K			      Show a bare listing of keywords by name.

   VERB LIST
	bar bootstrap cat check count-distinct count-similar cut decimate filter
	fraction grep group-by group-like having-fields head histogram join label
	least-frequent merge-fields most-frequent nest nothing put regularize rename
	reorder repeat reshape sample sec2gmt sec2gmtdate seqgen shuffle sort stats1
	stats2 step tac tail tee top uniq unsparsify

   FUNCTION LIST
	+ + - - * / // .+ .+ .- .- .* ./ .// % ** | ^ & ~ << >> bitcount == != =~ !=~
	> >= < <= && || ^^ ! ? : . gsub strlen sub substr tolower toupper abs acos
	acosh asin asinh atan atan2 atanh cbrt ceil cos cosh erf erfc exp expm1 floor
	invqnorm log log10 log1p logifit madd max mexp min mmul msub pow qnorm round
	roundm sgn sin sinh sqrt tan tanh urand urand32 urandint dhms2fsec dhms2sec
	fsec2dhms fsec2hms gmt2sec hms2fsec hms2sec sec2dhms sec2gmt sec2gmt
	sec2gmtdate sec2hms strftime strptime systime is_absent is_bool is_boolean
	is_empty is_empty_map is_float is_int is_map is_nonempty_map is_not_empty
	is_not_map is_not_null is_null is_numeric is_present is_string
	asserting_absent asserting_bool asserting_boolean asserting_empty
	asserting_empty_map asserting_float asserting_int asserting_map
	asserting_nonempty_map asserting_not_empty asserting_not_map
	asserting_not_null asserting_null asserting_numeric asserting_present
	asserting_string boolean float fmtnum hexfmt int string typeof depth haskey
	joink joinkv joinv leafcount length mapdiff mapexcept mapselect mapsum splitkv
	splitkvx splitnv splitnvx

       Please use "mlr --help-function {function name}" for function-specific help.

   I/O FORMATTING
	 --idkvp   --odkvp   --dkvp	 Delimited key-value pairs, e.g "a=1,b=2"
					 (this is Miller's default format).

	 --inidx   --onidx   --nidx	 Implicitly-integer-indexed fields
					 (Unix-toolkit style).
	 -T				 Synonymous with "--nidx --fs tab".

	 --icsv    --ocsv    --csv	 Comma-separated value (or tab-separated
					 with --fs tab, etc.)

	 --itsv    --otsv    --tsv	 Keystroke-savers for "--icsv --ifs tab",
					 "--ocsv --ofs tab", "--csv --fs tab".

	 --icsvlite --ocsvlite --csvlite Comma-separated value (or tab-separated
					 with --fs tab, etc.). The 'lite' CSV does not handle
					 RFC-CSV double-quoting rules; is slightly faster;
					 and handles heterogeneity in the input stream via
					 empty newline followed by new header line. See also
					 http://johnkerl.org/miller/doc/file-formats.html#CSV/TSV/etc.

	 --itsvlite --otsvlite --tsvlite Keystroke-savers for "--icsvlite --ifs tab",
					 "--ocsvlite --ofs tab", "--csvlite --fs tab".
	 -t				 Synonymous with --tsvlite.

	 --ipprint --opprint --pprint	 Pretty-printed tabular (produces no
					 output until all input is in).
			     --right	 Right-justifies all fields for PPRINT output.
			     --barred	 Prints a border around PPRINT output
					 (only available for output).

		   --omd		 Markdown-tabular (only available for output).

	 --ixtab   --oxtab   --xtab	 Pretty-printed vertical-tabular.
			     --xvright	 Right-justifies values for XTAB format.

	 --ijson   --ojson   --json	 JSON tabular: sequence or list of one-level
					 maps: {...}{...} or [{...},{...}].
	   --json-map-arrays-on-input	 JSON arrays are unmillerable. --json-map-arrays-on-input
	   --json-skip-arrays-on-input	 is the default: arrays are converted to integer-indexed
	   --json-fatal-arrays-on-input  maps. The other two options cause them to be skipped, or
					 to be treated as errors.  Please use the jq tool for full
					 JSON (pre)processing.
			     --jvstack	 Put one key-value pair per line for JSON
					 output.
			     --jlistwrap Wrap JSON output in outermost [ ].
			   --jknquoteint Do not quote non-string map keys in JSON output.
			    --jvquoteall Quote map values in JSON output, even if they're
					 numeric.
		     --jflatsep {string} Separator for flattening multi-level JSON keys,
					 e.g. '{"a":{"b":3}}' becomes a:b => 3 for
					 non-JSON formats. Defaults to :.

	 -p is a keystroke-saver for --nidx --fs space --repifs

	 --mmap --no-mmap --mmap-below {n} Use mmap for files whenever possible, never, or
					 for files less than n bytes in size. Default is for
					 files less than 4294967296 bytes in size.
					 'Whenever possible' means always except for when reading
					 standard input which is not mmappable. If you don't know
					 what this means, don't worry about it -- it's a minor
					 performance optimization.

	 Examples: --csv for CSV-formatted input and output; --idkvp --opprint for
	 DKVP-formatted input and pretty-printed output.

   COMMENTS IN DATA
	 --skip-comments		 Ignore commented lines (prefixed by "#")
					 within the input.
	 --skip-comments-with {string}	 Ignore commented lines within input, with
					 specified prefix.
	 --pass-comments		 Immediately print commented lines (prefixed by "#")
					 within the input.
	 --pass-comments-with {string}	 Immediately print commented lines within input, with
					 specified prefix.
       Notes:
       * Comments are only honored at the start of a line.
       * In the absence of any of the above four options, comments are data like
	 any other text.
       * When pass-comments is used, comment lines are written to standard output
	 immediately upon being read; they are not part of the record stream.
	 Results may be counterintuitive. A suggestion is to place comments at the
	 start of data files.

   FORMAT-CONVERSION KEYSTROKE-SAVERS
       As keystroke-savers for format-conversion you may use the following:
	 --c2t --c2d --c2n --c2j --c2x --c2p --c2m
	 --t2c	     --t2d --t2n --t2j --t2x --t2p --t2m
	 --d2c --d2t	   --d2n --d2j --d2x --d2p --d2m
	 --n2c --n2t --n2d	 --n2j --n2x --n2p --n2m
	 --j2c --j2t --j2d --j2n       --j2x --j2p --j2m
	 --x2c --x2t --x2d --x2n --x2j	     --x2p --x2m
	 --p2c --p2t --p2d --p2n --p2j --p2x	   --p2m
       The letters c t d n j x p m refer to formats CSV, TSV, DKVP, NIDX, JSON, XTAB,
       PPRINT, and markdown, respectively. Note that markdown format is available for
       output only.

   COMPRESSED I/O
	 --prepipe {command} This allows Miller to handle compressed inputs. You can do
	 without this for single input files, e.g. "gunzip < myfile.csv.gz | mlr ...".
	 However, when multiple input files are present, between-file separations are
	 lost; also, the FILENAME variable doesn't iterate. Using --prepipe you can
	 specify an action to be taken on each input file. This pre-pipe command must
	 be able to read from standard input; it will be invoked with
	   {command} < {filename}.
	 Examples:
	   mlr --prepipe 'gunzip'
	   mlr --prepipe 'zcat -cf'
	   mlr --prepipe 'xz -cd'
	   mlr --prepipe cat
	 Note that this feature is quite general and is not limited to decompression
	 utilities. You can use it to apply per-file filters of your choice.
	 For output compression (or other) utilities, simply pipe the output:
	   mlr ... | {your compression command}

   SEPARATORS
	 --rs	  --irs     --ors	       Record separators, e.g. 'lf' or '\r\n'
	 --fs	  --ifs     --ofs  --repifs    Field separators, e.g. comma
	 --ps	  --ips     --ops	       Pair separators, e.g. equals sign

	 Notes about line endings:
	 * Default line endings (--irs and --ors) are "auto" which means autodetect from
	   the input file format, as long as the input file(s) have lines ending in either
	   LF (also known as linefeed, '\n', 0x0a, Unix-style) or CRLF (also known as
	   carriage-return/linefeed pairs, '\r\n', 0x0d 0x0a, Windows style).
	 * If both irs and ors are auto (which is the default) then LF input will lead to LF
	   output and CRLF input will lead to CRLF output, regardless of the platform you're
	   running on.
	 * The line-ending autodetector triggers on the first line ending detected in the input
	   stream. E.g. if you specify a CRLF-terminated file on the command line followed by an
	   LF-terminated file then autodetected line endings will be CRLF.
	 * If you use --ors {something else} with (default or explicitly specified) --irs auto
	   then line endings are autodetected on input and set to what you specify on output.
	 * If you use --irs {something else} with (default or explicitly specified) --ors auto
	   then the output line endings used are LF on Unix/Linux/BSD/MacOSX, and CRLF on Windows.

	 Notes about all other separators:
	 * IPS/OPS are only used for DKVP and XTAB formats, since only in these formats
	   do key-value pairs appear juxtaposed.
	 * IRS/ORS are ignored for XTAB format. Nominally IFS and OFS are newlines;
	   XTAB records are separated by two or more consecutive IFS/OFS -- i.e.
	   a blank line. Everything above about --irs/--ors/--rs auto becomes --ifs/--ofs/--fs
	   auto for XTAB format. (XTAB's default IFS/OFS are "auto".)
	 * OFS must be single-character for PPRINT format. This is because it is used
	   with repetition for alignment; multi-character separators would make
	   alignment impossible.
	 * OPS may be multi-character for XTAB format, in which case alignment is
	   disabled.
	 * TSV is simply CSV using tab as field separator ("--fs tab").
	 * FS/PS are ignored for markdown format; RS is used.
	 * All FS and PS options are ignored for JSON format, since they are not relevant
	   to the JSON format.
	 * You can specify separators in any of the following ways, shown by example:
	   - Type them out, quoting as necessary for shell escapes, e.g.
	     "--fs '|' --ips :"
	   - C-style escape sequences, e.g. "--rs '\r\n' --fs '\t'".
	   - To avoid backslashing, you can use any of the following names:
	     cr crcr newline lf lflf crlf crlfcrlf tab space comma pipe slash colon semicolon equals
	 * Default separators by format:
	     File format  RS	   FS	    PS
	     gen	  N/A	   (N/A)    (N/A)
	     dkvp	  auto	   ,	    =
	     json	  auto	   (N/A)    (N/A)
	     nidx	  auto	   space    (N/A)
	     csv	  auto	   ,	    (N/A)
	     csvlite	  auto	   ,	    (N/A)
	     markdown	  auto	   (N/A)    (N/A)
	     pprint	  auto	   space    (N/A)
	     xtab	  (N/A)    auto     space

   CSV-SPECIFIC OPTIONS
	 --implicit-csv-header Use 1,2,3,... as field labels, rather than from line 1
			    of input files. Tip: combine with "label" to recreate
			    missing headers.
	 --headerless-csv-output   Print only CSV data lines.

   DOUBLE-QUOTING FOR CSV/CSVLITE OUTPUT
	 --quote-all	    Wrap all fields in double quotes
	 --quote-none	    Do not wrap any fields in double quotes, even if they have
			    OFS or ORS in them
	 --quote-minimal    Wrap fields in double quotes only if they have OFS or ORS
			    in them (default)
	 --quote-numeric    Wrap fields in double quotes only if they have numbers
			    in them
	 --quote-original   Wrap fields in double quotes if and only if they were
			    quoted on input. This isn't sticky for computed fields:
			    e.g. if fields a and b were quoted on input and you do
			    "put '$c = $a . $b'" then field c won't inherit a or b's
			    was-quoted-on-input flag.

   NUMERICAL FORMATTING
	 --ofmt {format}    E.g. %.18lf, %.0lf. Please use sprintf-style codes for
			    double-precision. Applies to verbs which compute new
			    values, e.g. put, stats1, stats2. See also the fmtnum
			    function within mlr put (mlr --help-all-functions).
			    Defaults to %lf.

   OTHER OPTIONS
	 --seed {n} with n of the form 12345678 or 0xcafefeed. For put/filter
			    urand()/urandint()/urand32().
	 --nr-progress-mod {m}, with m a positive integer: print filename and record
			    count to stderr every m input records.
	 --from {filename}  Use this to specify an input file before the verb(s),
			    rather than after. May be used more than once. Example:
			    "mlr --from a.dat --from b.dat cat" is the same as
			    "mlr cat a.dat b.dat".
	 -n		    Process no input files, nor standard input either. Useful
			    for mlr put with begin/end statements only. (Same as --from
			    /dev/null.) Also useful in "mlr -n put -v '...'" for
			    analyzing abstract syntax trees (if that's your thing).
	 -I		    Process files in-place. For each file name on the command
			    line, output is written to a temp file in the same
			    directory, which is then renamed over the original. Each
			    file is processed in isolation: if the output format is
			    CSV, CSV headers will be present in each output file;
			    statistics are only over each file's own records; and so on.

   THEN-CHAINING
       Output of one verb may be chained as input to another using "then", e.g.
	 mlr stats1 -a min,mean,max -f flag,u,v -g color then sort -f color

   AUXILIARY COMMANDS
       Miller has a few otherwise-standalone executables packaged within it.
       They do not participate in any other parts of Miller.
       Available subcommands:
	 aux-list
	 lecat
	 termcvt
	 hex
	 unhex
	 netbsd-strptime
       For more information, please invoke mlr {subcommand} --help

VERBS
   bar
       Usage: mlr bar [options]
       Replaces a numeric field with a number of asterisks, allowing for cheesy
       bar plots. These align best with --opprint or --oxtab output format.
       Options:
       -f   {a,b,c}	 Field names to convert to bars.
       -c   {character}  Fill character: default '*'.
       -x   {character}  Out-of-bounds character: default '#'.
       -b   {character}  Blank character: default '.'.
       --lo {lo}	 Lower-limit value for min-width bar: default '0.000000'.
       --hi {hi}	 Upper-limit value for max-width bar: default '100.000000'.
       -w   {n} 	 Bar-field width: default '40'.
       --auto		 Automatically computes limits, ignoring --lo and --hi.
			 Holds all records in memory before producing any output.

   bootstrap
       Usage: mlr bootstrap [options]
       Emits an n-sample, with replacement, of the input records.
       Options:
       -n {number} Number of samples to output. Defaults to number of input records.
		   Must be non-negative.
       See also mlr sample and mlr shuffle.

   cat
       Usage: mlr cat [options]
       Passes input records directly to output. Most useful for format conversion.
       Options:
       -n	 Prepend field "n" to each record with record-counter starting at 1
       -g {comma-separated field name(s)} When used with -n/-N, writes record-counters
		 keyed by specified field name(s).
       -N {name} Prepend field {name} to each record with record-counter starting at 1

   check
       Usage: mlr check
       Consumes records without printing any output.
       Useful for doing a well-formatted check on input data.

   count-distinct
       Usage: mlr count-distinct [options]
       -f {a,b,c}    Field names for distinct count.
       -n	     Show only the number of distinct values. Not compatible with -u.
       -o {name}     Field name for output count. Default "count".
		     Ignored with -u.
       -u	     Do unlashed counts for multiple field names. With -f a,b and
		     without -u, computes counts for distinct combinations of a
		     and b field values. With -f a,b and with -u, computes counts
		     for distinct a field values and counts for distinct b field
		     values separately.
       Prints number of records having distinct values for specified field names.
       Same as uniq -c.

   count-similar
       Usage: mlr count-similar [options]
       Ingests all records, then emits each record augmented by a count of
       the number of other records having the same group-by field values.
       Options:
       -g {d,e,f} Group-by-field names for counts.
       -o {name}  Field name for output count. Default "count".

   cut
       Usage: mlr cut [options]
       Passes through input records with specified fields included/excluded.
       -f {a,b,c}	Field names to include for cut.
       -o		Retain fields in the order specified here in the argument list.
			Default is to retain them in the order found in the input data.
       -x|--complement	Exclude, rather than include, field names specified by -f.
       -r		Treat field names as regular expressions. "ab", "a.*b" will
			match any field name containing the substring "ab" or matching
			"a.*b", respectively; anchors of the form "^ab$", "^a.*b$" may
			be used. The -o flag is ignored when -r is present.
       Examples:
	 mlr cut -f hostname,status
	 mlr cut -x -f hostname,status
	 mlr cut -r -f '^status$,sda[0-9]'
	 mlr cut -r -f '^status$,"sda[0-9]"'
	 mlr cut -r -f '^status$,"sda[0-9]"i' (this is case-insensitive)

   decimate
       Usage: mlr decimate [options]
       -n {count}    Decimation factor; default 10
       -b	     Decimate by printing first of every n.
       -e	     Decimate by printing last of every n (default).
       -g {a,b,c}    Optional group-by-field names for decimate counts
       Passes through one of every n records, optionally by category.

   filter
       Usage: mlr filter [options] {expression}
       Prints records for which {expression} evaluates to true.
       If there are multiple semicolon-delimited expressions, all of them are
       evaluated and the last one is used as the filter criterion.

       Conversion options:
       -S: Keeps field values as strings with no type inference to int or float.
       -F: Keeps field values as strings or floats with no inference to int.
       All field values are type-inferred to int/float/string unless this behavior is
       suppressed with -S or -F.

       Output/formatting options:
       --oflatsep {string}: Separator to use when flattening multi-level @-variables
	   to output records for emit. Default ":".
       --jknquoteint: For dump output (JSON-formatted), do not quote map keys if non-string.
       --jvquoteall: For dump output (JSON-formatted), quote map values even if non-string.
       Any of the output-format command-line flags (see mlr -h). Example: using
	 mlr --icsv --opprint ... then put --ojson 'tee > "mytap-".$a.".dat", $*' then ...
       the input is CSV, the output is pretty-print tabular, but the tee-file output
       is written in JSON format.
       --no-fflush: for emit, tee, print, and dump, don't call fflush() after every
	   record.

       Expression-specification options:
       -f {filename}: the DSL expression is taken from the specified file rather
	   than from the command line. Outer single quotes wrapping the expression
	   should not be placed in the file. If -f is specified more than once,
	   all input files specified using -f are concatenated to produce the expression.
	   (For example, you can define functions in one file and call them from another.)
       -e {expression}: You can use this after -f to add an expression. Example use
	   case: define functions/subroutines in a file you specify with -f, then call
	   them with an expression you specify with -e.
       (If you mix -e and -f then the expressions are evaluated in the order encountered.
       Since the expression pieces are simply concatenated, please be sure to use intervening
       semicolons to separate expressions.)

       Tracing options:
       -v: Prints the expressions's AST (abstract syntax tree), which gives
	   full transparency on the precedence and associativity rules of
	   Miller's grammar, to stdout.
       -a: Prints a low-level stack-allocation trace to stdout.
       -t: Prints a low-level parser trace to stderr.
       -T: Prints a every statement to stderr as it is executed.

       Other options:
       -x: Prints records for which {expression} evaluates to false.

       Please use a dollar sign for field names and double-quotes for string
       literals. If field names have special characters such as "." then you might
       use braces, e.g. '${field.name}'. Miller built-in variables are
       NF NR FNR FILENUM FILENAME M_PI M_E, and ENV["namegoeshere"] to access environment
       variables. The environment-variable name may be an expression, e.g. a field
       value.

       Use # to comment to end of line.

       Examples:
	 mlr filter 'log10($count) > 4.0'
	 mlr filter 'FNR == 2	       (second record in each file)'
	 mlr filter 'urand() < 0.001'  (subsampling)
	 mlr filter '$color != "blue" && $value > 4.2'
	 mlr filter '($x<.5 && $y<.5) || ($x>.5 && $y>.5)'
	 mlr filter '($name =~ "^sys.*east$") || ($name =~ "^dev.[0-9]+"i)'
	 mlr filter '$ab = $a+$b; $cd = $c+$d; $ab != $cd'
	 mlr filter '
	   NR == 1 ||
	  #NR == 2 ||
	   NR == 3
	 '

       Please see http://johnkerl.org/miller/doc/reference.html for more information
       including function list. Or "mlr -f". Please also also "mlr grep" which is
       useful when you don't yet know which field name(s) you're looking for.

   fraction
       Usage: mlr fraction [options]
       For each record's value in specified fields, computes the ratio of that
       value to the sum of values in that field over all input records.
       E.g. with input records	x=1  x=2  x=3  and  x=4, emits output records
       x=1,x_fraction=0.1  x=2,x_fraction=0.2  x=3,x_fraction=0.3  and	x=4,x_fraction=0.4

       Note: this is internally a two-pass algorithm: on the first pass it retains
       input records and accumulates sums; on the second pass it computes quotients
       and emits output records. This means it produces no output until all input is read.

       Options:
       -f {a,b,c}    Field name(s) for fraction calculation
       -g {d,e,f}    Optional group-by-field name(s) for fraction counts
       -p	     Produce percents [0..100], not fractions [0..1]. Output field names
		     end with "_percent" rather than "_fraction"
       -c	     Produce cumulative distributions, i.e. running sums: each output
		     value folds in the sum of the previous for the specified group
		     E.g. with input records  x=1  x=2	x=3  and  x=4, emits output records
		     x=1,x_cumulative_fraction=0.1  x=2,x_cumulative_fraction=0.3
		     x=3,x_cumulative_fraction=0.6  and  x=4,x_cumulative_fraction=1.0

   grep
       Usage: mlr grep [options] {regular expression}
       Passes through records which match {regex}.
       Options:
       -i    Use case-insensitive search.
       -v    Invert: pass through records which do not match the regex.
       Note that "mlr filter" is more powerful, but requires you to know field names.
       By contrast, "mlr grep" allows you to regex-match the entire record. It does
       this by formatting each record in memory as DKVP, using command-line-specified
       ORS/OFS/OPS, and matching the resulting line against the regex specified
       here. In particular, the regex is not applied to the input stream: if you
       have CSV with header line "x,y,z" and data line "1,2,3" then the regex will
       be matched, not against either of these lines, but against the DKVP line
       "x=1,y=2,z=3".  Furthermore, not all the options to system grep are supported,
       and this command is intended to be merely a keystroke-saver. To get all the
       features of system grep, you can do
	 "mlr --odkvp ... | grep ... | mlr --idkvp ..."

   group-by
       Usage: mlr group-by {comma-separated field names}
       Outputs records in batches having identical values at specified field names.

   group-like
       Usage: mlr group-like
       Outputs records in batches having identical field names.

   having-fields
       Usage: mlr having-fields [options]
       Conditionally passes through records depending on each record's field names.
       Options:
	 --at-least	 {comma-separated names}
	 --which-are	 {comma-separated names}
	 --at-most	 {comma-separated names}
	 --all-matching  {regular expression}
	 --any-matching  {regular expression}
	 --none-matching {regular expression}
       Examples:
	 mlr having-fields --which-are amount,status,owner
	 mlr having-fields --any-matching 'sda[0-9]'
	 mlr having-fields --any-matching '"sda[0-9]"'
	 mlr having-fields --any-matching '"sda[0-9]"i' (this is case-insensitive)

   head
       Usage: mlr head [options]
       -n {count}    Head count to print; default 10
       -g {a,b,c}    Optional group-by-field names for head counts
       Passes through the first n records, optionally by category.
       Without -g, ceases consuming more input (i.e. is fast) when n
       records have been read.

   histogram
       Usage: mlr histogram [options]
       -f {a,b,c}    Value-field names for histogram counts
       --lo {lo}     Histogram low value
       --hi {hi}     Histogram high value
       --nbins {n}   Number of histogram bins
       --auto	     Automatically computes limits, ignoring --lo and --hi.
		     Holds all values in memory before producing any output.
       -o {prefix}   Prefix for output field name. Default: no prefix.
       Just a histogram. Input values < lo or > hi are not counted.

   join
       Usage: mlr join [options]
       Joins records from specified left file name with records from all file names
       at the end of the Miller argument list.
       Functionality is essentially the same as the system "join" command, but for
       record streams.
       Options:
	 -f {left file name}
	 -j {a,b,c}   Comma-separated join-field names for output
	 -l {a,b,c}   Comma-separated join-field names for left input file;
		      defaults to -j values if omitted.
	 -r {a,b,c}   Comma-separated join-field names for right input file(s);
		      defaults to -j values if omitted.
	 --lp {text}  Additional prefix for non-join output field names from
		      the left file
	 --rp {text}  Additional prefix for non-join output field names from
		      the right file(s)
	 --np	      Do not emit paired records
	 --ul	      Emit unpaired records from the left file
	 --ur	      Emit unpaired records from the right file(s)
	 -s|--sorted-input  Require sorted input: records must be sorted
		      lexically by their join-field names, else not all records will
		      be paired. The only likely use case for this is with a left
		      file which is too big to fit into system memory otherwise.
	 -u	      Enable unsorted input. (This is the default even without -u.)
		      In this case, the entire left file will be loaded into memory.
	 --prepipe {command} As in main input options; see mlr --help for details.
		      If you wish to use a prepipe command for the main input as well
		      as here, it must be specified there as well as here.
       File-format options default to those for the right file names on the Miller
       argument list, but may be overridden for the left file as follows. Please see
       the main "mlr --help" for more information on syntax for these arguments.
	 -i {one of csv,dkvp,nidx,pprint,xtab}
	 --irs {record-separator character}
	 --ifs {field-separator character}
	 --ips {pair-separator character}
	 --repifs
	 --repips
	 --mmap
	 --no-mmap
       Please use "mlr --usage-separator-options" for information on specifying separators.
       Please see http://johnkerl.org/miller/doc/reference.html for more information
       including examples.

   label
       Usage: mlr label {new1,new2,new3,...}
       Given n comma-separated names, renames the first n fields of each record to
       have the respective name. (Fields past the nth are left with their original
       names.) Particularly useful with --inidx or --implicit-csv-header, to give
       useful names to otherwise integer-indexed fields.
       Examples:
	 "echo 'a b c d' | mlr --inidx --odkvp cat"	  gives "1=a,2=b,3=c,4=d"
	 "echo 'a b c d' | mlr --inidx --odkvp label s,t" gives "s=a,t=b,3=c,4=d"

   least-frequent
       Usage: mlr least-frequent [options]
       Shows the least frequently occurring distinct values for specified field names.
       The first entry is the statistical anti-mode; the remaining are runners-up.
       Options:
       -f {one or more comma-separated field names}. Required flag.
       -n {count}. Optional flag defaulting to 10.
       -b	   Suppress counts; show only field values.
       -o {name}   Field name for output count. Default "count".
       See also "mlr most-frequent".

   merge-fields
       Usage: mlr merge-fields [options]
       Computes univariate statistics for each input record, accumulated across
       specified fields.
       Options:
       -a {sum,count,...}  Names of accumulators. One or more of:
	 count	   Count instances of fields
	 mode	   Find most-frequently-occurring values for fields; first-found wins tie
	 antimode  Find least-frequently-occurring values for fields; first-found wins tie
	 sum	   Compute sums of specified fields
	 mean	   Compute averages (sample means) of specified fields
	 stddev    Compute sample standard deviation of specified fields
	 var	   Compute sample variance of specified fields
	 meaneb    Estimate error bars for averages (assuming no sample autocorrelation)
	 skewness  Compute sample skewness of specified fields
	 kurtosis  Compute sample kurtosis of specified fields
	 min	   Compute minimum values of specified fields
	 max	   Compute maximum values of specified fields
       -f {a,b,c}  Value-field names on which to compute statistics. Requires -o.
       -r {a,b,c}  Regular expressions for value-field names on which to compute
		   statistics. Requires -o.
       -c {a,b,c}  Substrings for collapse mode. All fields which have the same names
		   after removing substrings will be accumulated together. Please see
		   examples below.
       -i	   Use interpolated percentiles, like R's type=7; default like type=1.
		   Not sensical for string-valued fields.
       -o {name}   Output field basename for -f/-r.
       -k	   Keep the input fields which contributed to the output statistics;
		   the default is to omit them.
       -F	   Computes integerable things (e.g. count) in floating point.

       String-valued data make sense unless arithmetic on them is required,
       e.g. for sum, mean, interpolated percentiles, etc. In case of mixed data,
       numbers are less than strings.

       Example input data: "a_in_x=1,a_out_x=2,b_in_y=4,b_out_x=8".
       Example: mlr merge-fields -a sum,count -f a_in_x,a_out_x -o foo
	 produces "b_in_y=4,b_out_x=8,foo_sum=3,foo_count=2" since "a_in_x,a_out_x" are
	 summed over.
       Example: mlr merge-fields -a sum,count -r in_,out_ -o bar
	 produces "bar_sum=15,bar_count=4" since all four fields are summed over.
       Example: mlr merge-fields -a sum,count -c in_,out_
	 produces "a_x_sum=3,a_x_count=2,b_y_sum=4,b_y_count=1,b_x_sum=8,b_x_count=1"
	 since "a_in_x" and "a_out_x" both collapse to "a_x", "b_in_y" collapses to
	 "b_y", and "b_out_x" collapses to "b_x".

   most-frequent
       Usage: mlr most-frequent [options]
       Shows the most frequently occurring distinct values for specified field names.
       The first entry is the statistical mode; the remaining are runners-up.
       Options:
       -f {one or more comma-separated field names}. Required flag.
       -n {count}. Optional flag defaulting to 10.
       -b	   Suppress counts; show only field values.
       -o {name}   Field name for output count. Default "count".
       See also "mlr least-frequent".

   nest
       Usage: mlr nest [options]
       Explodes specified field values into separate fields/records, or reverses this.
       Options:
	 --explode,--implode   One is required.
	 --values,--pairs      One is required.
	 --across-records,--across-fields One is required.
	 -f {field name}       Required.
	 --nested-fs {string}  Defaults to ";". Field separator for nested values.
	 --nested-ps {string}  Defaults to ":". Pair separator for nested key-value pairs.
	 --evar {string}       Shorthand for --explode --values ---across-records --nested-fs {string}
       Please use "mlr --usage-separator-options" for information on specifying separators.

       Examples:

	 mlr nest --explode --values --across-records -f x
	 with input record "x=a;b;c,y=d" produces output records
	   "x=a,y=d"
	   "x=b,y=d"
	   "x=c,y=d"
	 Use --implode to do the reverse.

	 mlr nest --explode --values --across-fields -f x
	 with input record "x=a;b;c,y=d" produces output records
	   "x_1=a,x_2=b,x_3=c,y=d"
	 Use --implode to do the reverse.

	 mlr nest --explode --pairs --across-records -f x
	 with input record "x=a:1;b:2;c:3,y=d" produces output records
	   "a=1,y=d"
	   "b=2,y=d"
	   "c=3,y=d"

	 mlr nest --explode --pairs --across-fields -f x
	 with input record "x=a:1;b:2;c:3,y=d" produces output records
	   "a=1,b=2,c=3,y=d"

       Notes:
       * With --pairs, --implode doesn't make sense since the original field name has
	 been lost.
       * The combination "--implode --values --across-records" is non-streaming:
	 no output records are produced until all input records have been read. In
	 particular, this means it won't work in tail -f contexts. But all other flag
	 combinations result in streaming (tail -f friendly) data processing.
       * It's up to you to ensure that the nested-fs is distinct from your data's IFS:
	 e.g. by default the former is semicolon and the latter is comma.
       See also mlr reshape.

   nothing
       Usage: mlr nothing [options]
       Drops all input records. Useful for testing, or after tee/print/etc. have
       produced other output.

   put
       Usage: mlr put [options] {expression}
       Adds/updates specified field(s). Expressions are semicolon-separated and must
       either be assignments, or evaluate to boolean.  Booleans with following
       statements in curly braces control whether those statements are executed;
       booleans without following curly braces do nothing except side effects (e.g.
       regex-captures into \1, \2, etc.).

       Conversion options:
       -S: Keeps field values as strings with no type inference to int or float.
       -F: Keeps field values as strings or floats with no inference to int.
       All field values are type-inferred to int/float/string unless this behavior is
       suppressed with -S or -F.

       Output/formatting options:
       --oflatsep {string}: Separator to use when flattening multi-level @-variables
	   to output records for emit. Default ":".
       --jknquoteint: For dump output (JSON-formatted), do not quote map keys if non-string.
       --jvquoteall: For dump output (JSON-formatted), quote map values even if non-string.
       Any of the output-format command-line flags (see mlr -h). Example: using
	 mlr --icsv --opprint ... then put --ojson 'tee > "mytap-".$a.".dat", $*' then ...
       the input is CSV, the output is pretty-print tabular, but the tee-file output
       is written in JSON format.
       --no-fflush: for emit, tee, print, and dump, don't call fflush() after every
	   record.

       Expression-specification options:
       -f {filename}: the DSL expression is taken from the specified file rather
	   than from the command line. Outer single quotes wrapping the expression
	   should not be placed in the file. If -f is specified more than once,
	   all input files specified using -f are concatenated to produce the expression.
	   (For example, you can define functions in one file and call them from another.)
       -e {expression}: You can use this after -f to add an expression. Example use
	   case: define functions/subroutines in a file you specify with -f, then call
	   them with an expression you specify with -e.
       (If you mix -e and -f then the expressions are evaluated in the order encountered.
       Since the expression pieces are simply concatenated, please be sure to use intervening
       semicolons to separate expressions.)

       Tracing options:
       -v: Prints the expressions's AST (abstract syntax tree), which gives
	   full transparency on the precedence and associativity rules of
	   Miller's grammar, to stdout.
       -a: Prints a low-level stack-allocation trace to stdout.
       -t: Prints a low-level parser trace to stderr.
       -T: Prints a every statement to stderr as it is executed.

       Other options:
       -q: Does not include the modified record in the output stream. Useful for when
	   all desired output is in begin and/or end blocks.

       Please use a dollar sign for field names and double-quotes for string
       literals. If field names have special characters such as "." then you might
       use braces, e.g. '${field.name}'. Miller built-in variables are
       NF NR FNR FILENUM FILENAME M_PI M_E, and ENV["namegoeshere"] to access environment
       variables. The environment-variable name may be an expression, e.g. a field
       value.

       Use # to comment to end of line.

       Examples:
	 mlr put '$y = log10($x); $z = sqrt($y)'
	 mlr put '$x>0.0 { $y=log10($x); $z=sqrt($y) }' # does {...} only if $x > 0.0
	 mlr put '$x>0.0;  $y=log10($x); $z=sqrt($y)'	# does all three statements
	 mlr put '$a =~ "([a-z]+)_([0-9]+);  $b = "left_\1"; $c = "right_\2"'
	 mlr put '$a =~ "([a-z]+)_([0-9]+) { $b = "left_\1"; $c = "right_\2" }'
	 mlr put '$filename = FILENAME'
	 mlr put '$colored_shape = $color . "_" . $shape'
	 mlr put '$y = cos($theta); $z = atan2($y, $x)'
	 mlr put '$name = sub($name, "http.*com"i, "")'
	 mlr put -q '@sum += $x; end {emit @sum}'
	 mlr put -q '@sum[$a] += $x; end {emit @sum, "a"}'
	 mlr put -q '@sum[$a][$b] += $x; end {emit @sum, "a", "b"}'
	 mlr put -q '@min=min(@min,$x);@max=max(@max,$x); end{emitf @min, @max}'
	 mlr put -q 'is_null(@xmax) || $x > @xmax {@xmax=$x; @recmax=$*}; end {emit @recmax}'
	 mlr put '
	   $x = 1;
	  #$y = 2;
	   $z = 3
	 '

       Please see also 'mlr -k' for examples using redirected output.

       Please see http://johnkerl.org/miller/doc/reference.html for more information
       including function list. Or "mlr -f".
       Please see in particular:
	 http://www.johnkerl.org/miller/doc/reference.html#put

   regularize
       Usage: mlr regularize
       For records seen earlier in the data stream with same field names in
       a different order, outputs them with field names in the previously
       encountered order.
       Example: input records a=1,c=2,b=3, then e=4,d=5, then c=7,a=6,b=8
       output as	      a=1,c=2,b=3, then e=4,d=5, then a=6,c=7,b=8

   rename
       Usage: mlr rename [options] {old1,new1,old2,new2,...}
       Renames specified fields.
       Options:
       -r	  Treat old field  names as regular expressions. "ab", "a.*b"
		  will match any field name containing the substring "ab" or
		  matching "a.*b", respectively; anchors of the form "^ab$",
		  "^a.*b$" may be used. New field names may be plain strings,
		  or may contain capture groups of the form "\1" through
		  "\9". Wrapping the regex in double quotes is optional, but
		  is required if you wish to follow it with 'i' to indicate
		  case-insensitivity.
       -g	  Do global replacement within each field name rather than
		  first-match replacement.
       Examples:
       mlr rename old_name,new_name'
       mlr rename old_name_1,new_name_1,old_name_2,new_name_2'
       mlr rename -r 'Date_[0-9]+,Date,'  Rename all such fields to be "Date"
       mlr rename -r '"Date_[0-9]+",Date' Same
       mlr rename -r 'Date_([0-9]+).*,\1' Rename all such fields to be of the form 20151015
       mlr rename -r '"name"i,Name'	  Rename "name", "Name", "NAME", etc. to "Name"

   reorder
       Usage: mlr reorder [options]
       -f {a,b,c}   Field names to reorder.
       -e	    Put specified field names at record end: default is to put
		    them at record start.
       Examples:
       mlr reorder    -f a,b sends input record "d=4,b=2,a=1,c=3" to "a=1,b=2,d=4,c=3".
       mlr reorder -e -f a,b sends input record "d=4,b=2,a=1,c=3" to "d=4,c=3,a=1,b=2".

   repeat
       Usage: mlr repeat [options]
       Copies input records to output records multiple times.
       Options must be exactly one of the following:
	 -n {repeat count}  Repeat each input record this many times.
	 -f {field name}    Same, but take the repeat count from the specified
			    field name of each input record.
       Example:
	 echo x=0 | mlr repeat -n 4 then put '$x=urand()'
       produces:
	x=0.488189
	x=0.484973
	x=0.704983
	x=0.147311
       Example:
	 echo a=1,b=2,c=3 | mlr repeat -f b
       produces:
	 a=1,b=2,c=3
	 a=1,b=2,c=3
       Example:
	 echo a=1,b=2,c=3 | mlr repeat -f c
       produces:
	 a=1,b=2,c=3
	 a=1,b=2,c=3
	 a=1,b=2,c=3

   reshape
       Usage: mlr reshape [options]
       Wide-to-long options:
	 -i {input field names}   -o {key-field name,value-field name}
	 -r {input field regexes} -o {key-field name,value-field name}
	 These pivot/reshape the input data such that the input fields are removed
	 and separate records are emitted for each key/value pair.
	 Note: this works with tail -f and produces output records for each input
	 record seen.
       Long-to-wide options:
	 -s {key-field name,value-field name}
	 These pivot/reshape the input data to undo the wide-to-long operation.
	 Note: this does not work with tail -f; it produces output records only after
	 all input records have been read.

       Examples:

	 Input file "wide.txt":
	   time       X 	  Y
	   2009-01-01 0.65473572  2.4520609
	   2009-01-02 -0.89248112 0.2154713
	   2009-01-03 0.98012375  1.3179287

	 mlr --pprint reshape -i X,Y -o item,value wide.txt
	   time       item value
	   2009-01-01 X    0.65473572
	   2009-01-01 Y    2.4520609
	   2009-01-02 X    -0.89248112
	   2009-01-02 Y    0.2154713
	   2009-01-03 X    0.98012375
	   2009-01-03 Y    1.3179287

	 mlr --pprint reshape -r '[A-Z]' -o item,value wide.txt
	   time       item value
	   2009-01-01 X    0.65473572
	   2009-01-01 Y    2.4520609
	   2009-01-02 X    -0.89248112
	   2009-01-02 Y    0.2154713
	   2009-01-03 X    0.98012375
	   2009-01-03 Y    1.3179287

	 Input file "long.txt":
	   time       item value
	   2009-01-01 X    0.65473572
	   2009-01-01 Y    2.4520609
	   2009-01-02 X    -0.89248112
	   2009-01-02 Y    0.2154713
	   2009-01-03 X    0.98012375
	   2009-01-03 Y    1.3179287

	 mlr --pprint reshape -s item,value long.txt
	   time       X 	  Y
	   2009-01-01 0.65473572  2.4520609
	   2009-01-02 -0.89248112 0.2154713
	   2009-01-03 0.98012375  1.3179287
       See also mlr nest.

   sample
       Usage: mlr sample [options]
       Reservoir sampling (subsampling without replacement), optionally by category.
       -k {count}    Required: number of records to output, total, or by group if using -g.
       -g {a,b,c}    Optional: group-by-field names for samples.
       See also mlr bootstrap and mlr shuffle.

   sec2gmt
       Usage: mlr sec2gmt [options] {comma-separated list of field names}
       Replaces a numeric field representing seconds since the epoch with the
       corresponding GMT timestamp; leaves non-numbers as-is. This is nothing
       more than a keystroke-saver for the sec2gmt function:
	 mlr sec2gmt time1,time2
       is the same as
	 mlr put '$time1=sec2gmt($time1);$time2=sec2gmt($time2)'
       Options:
       -1 through -9: format the seconds using 1..9 decimal places, respectively.

   sec2gmtdate
       Usage: mlr sec2gmtdate {comma-separated list of field names}
       Replaces a numeric field representing seconds since the epoch with the
       corresponding GMT year-month-day timestamp; leaves non-numbers as-is.
       This is nothing more than a keystroke-saver for the sec2gmtdate function:
	 mlr sec2gmtdate time1,time2
       is the same as
	 mlr put '$time1=sec2gmtdate($time1);$time2=sec2gmtdate($time2)'

   seqgen
       Usage: mlr seqgen [options]
       Produces a sequence of counters.  Discards the input record stream. Produces
       output as specified by the following options:
       -f {name} Field name for counters; default "i".
       --start {number} Inclusive start value; default "1".
       --stop  {number} Inclusive stop value; default "100".
       --step  {number} Step value; default "1".
       Start, stop, and/or step may be floating-point. Output is integer if start,
       stop, and step are all integers. Step may be negative. It may not be zero
       unless start == stop.

   shuffle
       Usage: mlr shuffle {no options}
       Outputs records randomly permuted. No output records are produced until
       all input records are read.
       See also mlr bootstrap and mlr sample.

   sort
       Usage: mlr sort {flags}
       Flags:
	 -f  {comma-separated field names}  Lexical ascending
	 -n  {comma-separated field names}  Numerical ascending; nulls sort last
	 -nf {comma-separated field names}  Numerical ascending; nulls sort last
	 -r  {comma-separated field names}  Lexical descending
	 -nr {comma-separated field names}  Numerical descending; nulls sort first
       Sorts records primarily by the first specified field, secondarily by the second
       field, and so on.  (Any records not having all specified sort keys will appear
       at the end of the output, in the order they were encountered, regardless of the
       specified sort order.) The sort is stable: records that compare equal will sort
       in the order they were encountered in the input record stream.

       Example:
	 mlr sort -f a,b -nr x,y,z
       which is the same as:
	 mlr sort -f a -f b -nr x -nr y -nr z

   stats1
       Usage: mlr stats1 [options]
       Computes univariate statistics for one or more given fields, accumulated across
       the input record stream.
       Options:
       -a {sum,count,...}  Names of accumulators: p10 p25.2 p50 p98 p100 etc. and/or
			   one or more of:
	  count     Count instances of fields
	  mode	    Find most-frequently-occurring values for fields; first-found wins tie
	  antimode  Find least-frequently-occurring values for fields; first-found wins tie
	  sum	    Compute sums of specified fields
	  mean	    Compute averages (sample means) of specified fields
	  stddev    Compute sample standard deviation of specified fields
	  var	    Compute sample variance of specified fields
	  meaneb    Estimate error bars for averages (assuming no sample autocorrelation)
	  skewness  Compute sample skewness of specified fields
	  kurtosis  Compute sample kurtosis of specified fields
	  min	    Compute minimum values of specified fields
	  max	    Compute maximum values of specified fields
       -f {a,b,c}   Value-field names on which to compute statistics
       --fr {regex} Regex for value-field names on which to compute statistics
		    (compute statsitics on values in all field names matching regex)
       --fx {regex} Inverted regex for value-field names on which to compute statistics
		    (compute statsitics on values in all field names not matching regex)
       -g {d,e,f}   Optional group-by-field names
       --gr {regex} Regex for optional group-by-field names
		    (group by values in field names matching regex)
       --gx {regex} Inverted regex for optional group-by-field names
		    (group by values in field names not matching regex)
       --grfx {regex} Shorthand for --gr {regex} --fx {that same regex}
       -i	    Use interpolated percentiles, like R's type=7; default like type=1.
		    Not sensical for string-valued fields.
       -s	    Print iterative stats. Useful in tail -f contexts (in which
		    case please avoid pprint-format output since end of input
		    stream will never be seen).
       -F	    Computes integerable things (e.g. count) in floating point.
       Example: mlr stats1 -a min,p10,p50,p90,max -f value -g size,shape
       Example: mlr stats1 -a count,mode -f size
       Example: mlr stats1 -a count,mode -f size -g shape
       Example: mlr stats1 -a count,mode --fr '^[a-h].*$' -gr '^k.*$'
		This computes count and mode statistics on all field names beginning
		with a through h, grouped by all field names starting with k.
       Notes:
       * p50 and median are synonymous.
       * min and max output the same results as p0 and p100, respectively, but use
	 less memory.
       * String-valued data make sense unless arithmetic on them is required,
	 e.g. for sum, mean, interpolated percentiles, etc. In case of mixed data,
	 numbers are less than strings.
       * count and mode allow text input; the rest require numeric input.
	 In particular, 1 and 1.0 are distinct text for count and mode.
       * When there are mode ties, the first-encountered datum wins.

   stats2
       Usage: mlr stats2 [options]
       Computes bivariate statistics for one or more given field-name pairs,
       accumulated across the input record stream.
       -a {linreg-ols,corr,...}  Names of accumulators: one or more of:
	 linreg-pca   Linear regression using principal component analysis
	 linreg-ols   Linear regression using ordinary least squares
	 r2	      Quality metric for linreg-ols (linreg-pca emits its own)
	 logireg      Logistic regression
	 corr	      Sample correlation
	 cov	      Sample covariance
	 covx	      Sample-covariance matrix
       -f {a,b,c,d}   Value-field name-pairs on which to compute statistics.
		      There must be an even number of names.
       -g {e,f,g}     Optional group-by-field names.
       -v	      Print additional output for linreg-pca.
       -s	      Print iterative stats. Useful in tail -f contexts (in which
		      case please avoid pprint-format output since end of input
		      stream will never be seen).
       --fit	      Rather than printing regression parameters, applies them to
		      the input data to compute new fit fields. All input records are
		      held in memory until end of input stream. Has effect only for
		      linreg-ols, linreg-pca, and logireg.
       Only one of -s or --fit may be used.
       Example: mlr stats2 -a linreg-pca -f x,y
       Example: mlr stats2 -a linreg-ols,r2 -f x,y -g size,shape
       Example: mlr stats2 -a corr -f x,y

   step
       Usage: mlr step [options]
       Computes values dependent on the previous record, optionally grouped
       by category.

       Options:
       -a {delta,rsum,...}   Names of steppers: comma-separated, one or more of:
	 delta	  Compute differences in field(s) between successive records
	 shift	  Include value(s) in field(s) from previous record, if any
	 from-first Compute differences in field(s) from first record
	 ratio	  Compute ratios in field(s) between successive records
	 rsum	  Compute running sums of field(s) between successive records
	 counter  Count instances of field(s) between successive records
	 ewma	  Exponentially weighted moving average over successive records
       -f {a,b,c} Value-field names on which to compute statistics
       -g {d,e,f} Optional group-by-field names
       -F	  Computes integerable things (e.g. counter) in floating point.
       -d {x,y,z} Weights for ewma. 1 means current sample gets all weight (no
		  smoothing), near under under 1 is light smoothing, near over 0 is
		  heavy smoothing. Multiple weights may be specified, e.g.
		  "mlr step -a ewma -f sys_load -d 0.01,0.1,0.9". Default if omitted
		  is "-d 0.5".
       -o {a,b,c} Custom suffixes for EWMA output fields. If omitted, these default to
		  the -d values. If supplied, the number of -o values must be the same
		  as the number of -d values.

       Examples:
	 mlr step -a rsum -f request_size
	 mlr step -a delta -f request_size -g hostname
	 mlr step -a ewma -d 0.1,0.9 -f x,y
	 mlr step -a ewma -d 0.1,0.9 -o smooth,rough -f x,y
	 mlr step -a ewma -d 0.1,0.9 -o smooth,rough -f x,y -g group_name

       Please see http://johnkerl.org/miller/doc/reference.html#filter or
       https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
       for more information on EWMA.

   tac
       Usage: mlr tac
       Prints records in reverse order from the order in which they were encountered.

   tail
       Usage: mlr tail [options]
       -n {count}    Tail count to print; default 10
       -g {a,b,c}    Optional group-by-field names for tail counts
       Passes through the last n records, optionally by category.

   tee
       Usage: mlr tee [options] {filename}
       Passes through input records (like mlr cat) but also writes to specified output
       file, using output-format flags from the command line (e.g. --ocsv). See also
       the "tee" keyword within mlr put, which allows data-dependent filenames.
       Options:
       -a:	    append to existing file, if any, rather than overwriting.
       --no-fflush: don't call fflush() after every record.
       Any of the output-format command-line flags (see mlr -h). Example: using
	 mlr --icsv --opprint put '...' then tee --ojson ./mytap.dat then stats1 ...
       the input is CSV, the output is pretty-print tabular, but the tee-file output
       is written in JSON format.

   top
       Usage: mlr top [options]
       -f {a,b,c}    Value-field names for top counts.
       -g {d,e,f}    Optional group-by-field names for top counts.
       -n {count}    How many records to print per category; default 1.
       -a	     Print all fields for top-value records; default is
		     to print only value and group-by fields. Requires a single
		     value-field name only.
       --min	     Print top smallest values; default is top largest values.
       -F	     Keep top values as floats even if they look like integers.
       -o {name}     Field name for output indices. Default "top_idx".
       Prints the n records with smallest/largest values at specified fields,
       optionally by category.

   uniq
       Usage: mlr uniq [options]
       -g {d,e,f}    Group-by-field names for uniq counts.
       -c	     Show repeat counts in addition to unique values.
       -n	     Show only the number of distinct values.
       -o {name}     Field name for output count. Default "count".
       Prints distinct values for specified field names. With -c, same as
       count-distinct. For uniq, -f is a synonym for -g.

   unsparsify
       Usage: mlr unsparsify [options]
       Prints records with the union of field names over all input records.
       For field names absent in a given record but present in others, fills in
       a value. This verb retains all input before producing any output.

       Options:
       --fill-with {filler string}  What to fill absent fields with. Defaults to
				    the empty string.

       Example: if the input is two records, one being 'a=1,b=2' and the other
       being 'b=3,c=4', then the output is the two records 'a=1,b=2,c=' and

FUNCTIONS FOR FILTER/PUT
   +
       (class=arithmetic #args=2): Addition.

       + (class=arithmetic #args=1): Unary plus.

   -
       (class=arithmetic #args=2): Subtraction.

       - (class=arithmetic #args=1): Unary minus.

   *
       (class=arithmetic #args=2): Multiplication.

   /
       (class=arithmetic #args=2): Division.

   //
       (class=arithmetic #args=2): Integer division: rounds to negative (pythonic).

   .+
       (class=arithmetic #args=2): Addition, with integer-to-integer overflow

       .+ (class=arithmetic #args=1): Unary plus, with integer-to-integer overflow.

   .-
       (class=arithmetic #args=2): Subtraction, with integer-to-integer overflow.

       .- (class=arithmetic #args=1): Unary minus, with integer-to-integer overflow.

   .*
       (class=arithmetic #args=2): Multiplication, with integer-to-integer overflow.

   ./
       (class=arithmetic #args=2): Division, with integer-to-integer overflow.

   .//
       (class=arithmetic #args=2): Integer division: rounds to negative (pythonic), with integer-to-integer overflow.

   %
       (class=arithmetic #args=2): Remainder; never negative-valued (pythonic).

   **
       (class=arithmetic #args=2): Exponentiation; same as pow, but as an infix
       operator.

   |
       (class=arithmetic #args=2): Bitwise OR.

   ^
       (class=arithmetic #args=2): Bitwise XOR.

   &
       (class=arithmetic #args=2): Bitwise AND.

   ~
       (class=arithmetic #args=1): Bitwise NOT. Beware '$y=~$x' since =~ is the
       regex-match operator: try '$y = ~$x'.

   <<
       (class=arithmetic #args=2): Bitwise left-shift.

   >>
       (class=arithmetic #args=2): Bitwise right-shift.

   bitcount
       (class=arithmetic #args=1): Count of 1-bits

   ==
       (class=boolean #args=2): String/numeric equality. Mixing number and string
       results in string compare.

   !=
       (class=boolean #args=2): String/numeric inequality. Mixing number and string
       results in string compare.

   =~
       (class=boolean #args=2): String (left-hand side) matches regex (right-hand
       side), e.g. '$name =~ "^a.*b$"'.

   !=~
       (class=boolean #args=2): String (left-hand side) does not match regex
       (right-hand side), e.g. '$name !=~ "^a.*b$"'.

   >
       (class=boolean #args=2): String/numeric greater-than. Mixing number and string
       results in string compare.

   >=
       (class=boolean #args=2): String/numeric greater-than-or-equals. Mixing number
       and string results in string compare.

   <
       (class=boolean #args=2): String/numeric less-than. Mixing number and string
       results in string compare.

   <=
       (class=boolean #args=2): String/numeric less-than-or-equals. Mixing number
       and string results in string compare.

   &&
       (class=boolean #args=2): Logical AND.

   ||
       (class=boolean #args=2): Logical OR.

   ^^
       (class=boolean #args=2): Logical XOR.

   !
       (class=boolean #args=1): Logical negation.

   ? :
       (class=boolean #args=3): Ternary operator.

   .
       (class=string #args=2): String concatenation.

   gsub
       (class=string #args=3): Example: '$name=gsub($name, "old", "new")'
       (replace all).

   strlen
       (class=string #args=1): String length.

   sub
       (class=string #args=3): Example: '$name=sub($name, "old", "new")'
       (replace once).

   substr
       (class=string #args=3): substr(s,m,n) gives substring of s from 0-up position m to n
       inclusive. Negative indices -len .. -1 alias to 0 .. len-1.

   tolower
       (class=string #args=1): Convert string to lowercase.

   toupper
       (class=string #args=1): Convert string to uppercase.

   abs
       (class=math #args=1): Absolute value.

   acos
       (class=math #args=1): Inverse trigonometric cosine.

   acosh
       (class=math #args=1): Inverse hyperbolic cosine.

   asin
       (class=math #args=1): Inverse trigonometric sine.

   asinh
       (class=math #args=1): Inverse hyperbolic sine.

   atan
       (class=math #args=1): One-argument arctangent.

   atan2
       (class=math #args=2): Two-argument arctangent.

   atanh
       (class=math #args=1): Inverse hyperbolic tangent.

   cbrt
       (class=math #args=1): Cube root.

   ceil
       (class=math #args=1): Ceiling: nearest integer at or above.

   cos
       (class=math #args=1): Trigonometric cosine.

   cosh
       (class=math #args=1): Hyperbolic cosine.

   erf
       (class=math #args=1): Error function.

   erfc
       (class=math #args=1): Complementary error function.

   exp
       (class=math #args=1): Exponential function e**x.

   expm1
       (class=math #args=1): e**x - 1.

   floor
       (class=math #args=1): Floor: nearest integer at or below.

   invqnorm
       (class=math #args=1): Inverse of normal cumulative distribution
       function. Note that invqorm(urand()) is normally distributed.

   log
       (class=math #args=1): Natural (base-e) logarithm.

   log10
       (class=math #args=1): Base-10 logarithm.

   log1p
       (class=math #args=1): log(1-x).

   logifit
       (class=math #args=3): Given m and b from logistic regression, compute
       fit: $yhat=logifit($x,$m,$b).

   madd
       (class=math #args=3): a + b mod m (integers)

   max
       (class=math variadic): max of n numbers; null loses

   mexp
       (class=math #args=3): a ** b mod m (integers)

   min
       (class=math variadic): Min of n numbers; null loses

   mmul
       (class=math #args=3): a * b mod m (integers)

   msub
       (class=math #args=3): a - b mod m (integers)

   pow
       (class=math #args=2): Exponentiation; same as **.

   qnorm
       (class=math #args=1): Normal cumulative distribution function.

   round
       (class=math #args=1): Round to nearest integer.

   roundm
       (class=math #args=2): Round to nearest multiple of m: roundm($x,$m) is
       the same as round($x/$m)*$m

   sgn
       (class=math #args=1): +1 for positive input, 0 for zero input, -1 for
       negative input.

   sin
       (class=math #args=1): Trigonometric sine.

   sinh
       (class=math #args=1): Hyperbolic sine.

   sqrt
       (class=math #args=1): Square root.

   tan
       (class=math #args=1): Trigonometric tangent.

   tanh
       (class=math #args=1): Hyperbolic tangent.

   urand
       (class=math #args=0): Floating-point numbers on the unit interval.
       Int-valued example: '$n=floor(20+urand()*11)'.

   urand32
       (class=math #args=0): Integer uniformly distributed 0 and 2**32-1
       inclusive.

   urandint
       (class=math #args=2): Integer uniformly distributed between inclusive
       integer endpoints.

   dhms2fsec
       (class=time #args=1): Recovers floating-point seconds as in
       dhms2fsec("5d18h53m20.250000s") = 500000.250000

   dhms2sec
       (class=time #args=1): Recovers integer seconds as in
       dhms2sec("5d18h53m20s") = 500000

   fsec2dhms
       (class=time #args=1): Formats floating-point seconds as in
       fsec2dhms(500000.25) = "5d18h53m20.250000s"

   fsec2hms
       (class=time #args=1): Formats floating-point seconds as in
       fsec2hms(5000.25) = "01:23:20.250000"

   gmt2sec
       (class=time #args=1): Parses GMT timestamp as integer seconds since
       the epoch.

   hms2fsec
       (class=time #args=1): Recovers floating-point seconds as in
       hms2fsec("01:23:20.250000") = 5000.250000

   hms2sec
       (class=time #args=1): Recovers integer seconds as in
       hms2sec("01:23:20") = 5000

   sec2dhms
       (class=time #args=1): Formats integer seconds as in sec2dhms(500000)
       = "5d18h53m20s"

   sec2gmt
       (class=time #args=1): Formats seconds since epoch (integer part)
       as GMT timestamp, e.g. sec2gmt(1440768801.7) = "2015-08-28T13:33:21Z".
       Leaves non-numbers as-is.

       sec2gmt (class=time #args=2): Formats seconds since epoch as GMT timestamp with n
       decimal places for seconds, e.g. sec2gmt(1440768801.7,1) = "2015-08-28T13:33:21.7Z".
       Leaves non-numbers as-is.

   sec2gmtdate
       (class=time #args=1): Formats seconds since epoch (integer part)
       as GMT timestamp with year-month-date, e.g. sec2gmtdate(1440768801.7) = "2015-08-28".
       Leaves non-numbers as-is.

   sec2hms
       (class=time #args=1): Formats integer seconds as in
       sec2hms(5000) = "01:23:20"

   strftime
       (class=time #args=2): Formats seconds since the epoch as timestamp, e.g.
       strftime(1440768801.7,"%Y-%m-%dT%H:%M:%SZ") = "2015-08-28T13:33:21Z", and
       strftime(1440768801.7,"%Y-%m-%dT%H:%M:%3SZ") = "2015-08-28T13:33:21.700Z".
       Format strings are as in the C library (please see "man strftime" on your system),
       with the Miller-specific addition of "%1S" through "%9S" which format the seocnds
       with 1 through 9 decimal places, respectively. ("%S" uses no decimal places.)

   strptime
       (class=time #args=2): Parses timestamp as floating-point seconds since the epoch,
       e.g. strptime("2015-08-28T13:33:21Z","%Y-%m-%dT%H:%M:%SZ") = 1440768801.000000,
       and  strptime("2015-08-28T13:33:21.345Z","%Y-%m-%dT%H:%M:%SZ") = 1440768801.345000.

   systime
       (class=time #args=0): Floating-point seconds since the epoch,
       e.g. 1440768801.748936.

   is_absent
       (class=typing #args=1): False if field is present in input, false otherwise

   is_bool
       (class=typing #args=1): True if field is present with boolean value. Synonymous with is_boolean.

   is_boolean
       (class=typing #args=1): True if field is present with boolean value. Synonymous with is_bool.

   is_empty
       (class=typing #args=1): True if field is present in input with empty string value, false otherwise.

   is_empty_map
       (class=typing #args=1): True if argument is a map which is empty.

   is_float
       (class=typing #args=1): True if field is present with value inferred to be float

   is_int
       (class=typing #args=1): True if field is present with value inferred to be int

   is_map
       (class=typing #args=1): True if argument is a map.

   is_nonempty_map
       (class=typing #args=1): True if argument is a map which is non-empty.

   is_not_empty
       (class=typing #args=1): False if field is present in input with empty value, false otherwise

   is_not_map
       (class=typing #args=1): True if argument is not a map.

   is_not_null
       (class=typing #args=1): False if argument is null (empty or absent), true otherwise.

   is_null
       (class=typing #args=1): True if argument is null (empty or absent), false otherwise.

   is_numeric
       (class=typing #args=1): True if field is present with value inferred to be int or float

   is_present
       (class=typing #args=1): True if field is present in input, false otherwise.

   is_string
       (class=typing #args=1): True if field is present with string (including empty-string) value

   asserting_absent
       (class=typing #args=1): Returns argument if it is absent in the input data, else
       throws an error.

   asserting_bool
       (class=typing #args=1): Returns argument if it is present with boolean value, else
       throws an error.

   asserting_boolean
       (class=typing #args=1): Returns argument if it is present with boolean value, else
       throws an error.

   asserting_empty
       (class=typing #args=1): Returns argument if it is present in input with empty value,
       else throws an error.

   asserting_empty_map
       (class=typing #args=1): Returns argument if it is a map with empty value, else
       throws an error.

   asserting_float
       (class=typing #args=1): Returns argument if it is present with float value, else
       throws an error.

   asserting_int
       (class=typing #args=1): Returns argument if it is present with int value, else
       throws an error.

   asserting_map
       (class=typing #args=1): Returns argument if it is a map, else throws an error.

   asserting_nonempty_map
       (class=typing #args=1): Returns argument if it is a non-empty map, else throws
       an error.

   asserting_not_empty
       (class=typing #args=1): Returns argument if it is present in input with non-empty
       value, else throws an error.

   asserting_not_map
       (class=typing #args=1): Returns argument if it is not a map, else throws an error.

   asserting_not_null
       (class=typing #args=1): Returns argument if it is non-null (non-empty and non-absent),
       else throws an error.

   asserting_null
       (class=typing #args=1): Returns argument if it is null (empty or absent), else throws
       an error.

   asserting_numeric
       (class=typing #args=1): Returns argument if it is present with int or float value,
       else throws an error.

   asserting_present
       (class=typing #args=1): Returns argument if it is present in input, else throws
       an error.

   asserting_string
       (class=typing #args=1): Returns argument if it is present with string (including
       empty-string) value, else throws an error.

   boolean
       (class=conversion #args=1): Convert int/float/bool/string to boolean.

   float
       (class=conversion #args=1): Convert int/float/bool/string to float.

   fmtnum
       (class=conversion #args=2): Convert int/float/bool to string using
       printf-style format string, e.g. '$s = fmtnum($n, "%06lld")'. WARNING: Miller numbers
       are all long long or double. If you use formats like %d or %f, behavior is undefined.

   hexfmt
       (class=conversion #args=1): Convert int to string, e.g. 255 to "0xff".

   int
       (class=conversion #args=1): Convert int/float/bool/string to int.

   string
       (class=conversion #args=1): Convert int/float/bool/string to string.

   typeof
       (class=conversion #args=1): Convert argument to type of argument (e.g.
       MT_STRING). For debug.

   depth
       (class=maps #args=1): Prints maximum depth of hashmap: ''. Scalars have depth 0.

   haskey
       (class=maps #args=2): True/false if map has/hasn't key, e.g. 'haskey($*, "a")' or

   joink
       (class=maps #args=2): Makes string from map keys. E.g. 'joink($*, ",")'.

   joinkv
       (class=maps #args=3): Makes string from map key-value pairs. E.g. 'joinkv(@v[2], "=", ",")'

   joinv
       (class=maps #args=2): Makes string from map keys. E.g. 'joinv(mymap, ",")'.

   leafcount
       (class=maps #args=1): Counts total number of terminal values in hashmap. For single-level maps,
       same as length.

   length
       (class=maps #args=1): Counts number of top-level entries in hashmap. Scalars have length 1.

   mapdiff
       (class=maps variadic): With 0 args, returns empty map. With 1 arg, returns copy of arg.
       With 2 or more, returns copy of arg 1 with all keys from any of remaining argument maps removed.

   mapexcept
       (class=maps variadic): Returns a map with keys from remaining arguments, if any, unset.
       E.g. 'mapexcept({1:2,3:4,5:6}, 1, 5, 7)' is '{3:4}'.

   mapselect
       (class=maps variadic): Returns a map with only keys from remaining arguments set.
       E.g. 'mapselect({1:2,3:4,5:6}, 1, 5, 7)' is '{1:2,5:6}'.

   mapsum
       (class=maps variadic): With 0 args, returns empty map. With >= 1 arg, returns a map with
       key-value pairs from all arguments. Rightmost collisions win, e.g. 'mapsum({1:2,3:4},{1:5})' is '{1:5,3:4}'.

   splitkv
       (class=maps #args=3): Splits string by separators into map with type inference.
       E.g. 'splitkv("a=1,b=2,c=3", "=", ",")' gives '{"a" : 1, "b" : 2, "c" : 3}'.

   splitkvx
       (class=maps #args=3): Splits string by separators into map without type inference (keys and
       values are strings). E.g. 'splitkv("a=1,b=2,c=3", "=", ",")' gives

   splitnv
       (class=maps #args=2): Splits string by separator into integer-indexed map with type inference.
       E.g. 'splitnv("a,b,c" , ",")' gives '{1 : "a", 2 : "b", 3 : "c"}'.

   splitnvx
       (class=maps #args=2): Splits string by separator into integer-indexed map without type
       inference (values are strings). E.g. 'splitnv("4,5,6" , ",")' gives '{1 : "4", 2 : "5", 3 : "6"}'.

KEYWORDS FOR PUT AND FILTER
   all
       all: used in "emit", "emitp", and "unset" as a synonym for @*

   begin
       begin: defines a block of statements to be executed before input records
       are ingested. The body statements must be wrapped in curly braces.
       Example: 'begin { @count = 0 }'

   bool
       bool: declares a boolean local variable in the current curly-braced scope.
       Type-checking happens at assignment: 'bool b = 1' is an error.

   break
       break: causes execution to continue after the body of the current
       for/while/do-while loop.

   call
       call: used for invoking a user-defined subroutine.
       Example: 'subr s(k,v) { print k . " is " . v} call s("a", $a)'

   continue
       continue: causes execution to skip the remaining statements in the body of
       the current for/while/do-while loop. For-loop increments are still applied.

   do
       do: with "while", introduces a do-while loop. The body statements must be wrapped
       in curly braces.

   dump
       dump: prints all currently defined out-of-stream variables immediately
	 to stdout as JSON.

	 With >, >>, or |, the data do not become part of the output record stream but
	 are instead redirected.

	 The > and >> are for write and append, as in the shell, but (as with awk) the
	 file-overwrite for > is on first write, not per record. The | is for piping to
	 a process which will process the data. There will be one open file for each
	 distinct file name (for > and >>) or one subordinate process for each distinct
	 value of the piped-to command (for |). Output-formatting flags are taken from
	 the main command line.

	 Example: mlr --from f.dat put -q '@v[NR]=$*; end { dump }'
	 Example: mlr --from f.dat put -q '@v[NR]=$*; end { dump >  "mytap.dat"}'
	 Example: mlr --from f.dat put -q '@v[NR]=$*; end { dump >> "mytap.dat"}'
	 Example: mlr --from f.dat put -q '@v[NR]=$*; end { dump | "jq .[]"}'

   edump
       edump: prints all currently defined out-of-stream variables immediately
	 to stderr as JSON.

	 Example: mlr --from f.dat put -q '@v[NR]=$*; end { edump }'

   elif
       elif: the way Miller spells "else if". The body statements must be wrapped
       in curly braces.

   else
       else: terminates an if/elif/elif chain. The body statements must be wrapped
       in curly braces.

   emit
       emit: inserts an out-of-stream variable into the output record stream. Hashmap
	 indices present in the data but not slotted by emit arguments are not output.

	 With >, >>, or |, the data do not become part of the output record stream but
	 are instead redirected.

	 The > and >> are for write and append, as in the shell, but (as with awk) the
	 file-overwrite for > is on first write, not per record. The | is for piping to
	 a process which will process the data. There will be one open file for each
	 distinct file name (for > and >>) or one subordinate process for each distinct
	 value of the piped-to command (for |). Output-formatting flags are taken from
	 the main command line.

	 You can use any of the output-format command-line flags, e.g. --ocsv, --ofs,
	 etc., to control the format of the output if the output is redirected. See also mlr -h.

	 Example: mlr --from f.dat put 'emit >	"/tmp/data-".$a, $*'
	 Example: mlr --from f.dat put 'emit >	"/tmp/data-".$a, mapexcept($*, "a")'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit @sums'
	 Example: mlr --from f.dat put --ojson '@sums[$a][$b]+=$x; emit > "tap-".$a.$b.".dat", @sums'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit @sums, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit >  "mytap.dat", @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit >> "mytap.dat", @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit | "gzip > mytap.dat.gz", @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit > stderr, @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emit | "grep somepattern", @*, "index1", "index2"'

	 Please see http://johnkerl.org/miller/doc for more information.

   emitf
       emitf: inserts non-indexed out-of-stream variable(s) side-by-side into the
	 output record stream.

	 With >, >>, or |, the data do not become part of the output record stream but
	 are instead redirected.

	 The > and >> are for write and append, as in the shell, but (as with awk) the
	 file-overwrite for > is on first write, not per record. The | is for piping to
	 a process which will process the data. There will be one open file for each
	 distinct file name (for > and >>) or one subordinate process for each distinct
	 value of the piped-to command (for |). Output-formatting flags are taken from
	 the main command line.

	 You can use any of the output-format command-line flags, e.g. --ocsv, --ofs,
	 etc., to control the format of the output if the output is redirected. See also mlr -h.

	 Example: mlr --from f.dat put '@a=$i;@b+=$x;@c+=$y; emitf @a'
	 Example: mlr --from f.dat put --oxtab '@a=$i;@b+=$x;@c+=$y; emitf > "tap-".$i.".dat", @a'
	 Example: mlr --from f.dat put '@a=$i;@b+=$x;@c+=$y; emitf @a, @b, @c'
	 Example: mlr --from f.dat put '@a=$i;@b+=$x;@c+=$y; emitf > "mytap.dat", @a, @b, @c'
	 Example: mlr --from f.dat put '@a=$i;@b+=$x;@c+=$y; emitf >> "mytap.dat", @a, @b, @c'
	 Example: mlr --from f.dat put '@a=$i;@b+=$x;@c+=$y; emitf > stderr, @a, @b, @c'
	 Example: mlr --from f.dat put '@a=$i;@b+=$x;@c+=$y; emitf | "grep somepattern", @a, @b, @c'
	 Example: mlr --from f.dat put '@a=$i;@b+=$x;@c+=$y; emitf | "grep somepattern > mytap.dat", @a, @b, @c'

	 Please see http://johnkerl.org/miller/doc for more information.

   emitp
       emitp: inserts an out-of-stream variable into the output record stream.
	 Hashmap indices present in the data but not slotted by emitp arguments are
	 output concatenated with ":".

	 With >, >>, or |, the data do not become part of the output record stream but
	 are instead redirected.

	 The > and >> are for write and append, as in the shell, but (as with awk) the
	 file-overwrite for > is on first write, not per record. The | is for piping to
	 a process which will process the data. There will be one open file for each
	 distinct file name (for > and >>) or one subordinate process for each distinct
	 value of the piped-to command (for |). Output-formatting flags are taken from
	 the main command line.

	 You can use any of the output-format command-line flags, e.g. --ocsv, --ofs,
	 etc., to control the format of the output if the output is redirected. See also mlr -h.

	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp @sums'
	 Example: mlr --from f.dat put --opprint '@sums[$a][$b]+=$x; emitp > "tap-".$a.$b.".dat", @sums'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp @sums, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp >  "mytap.dat", @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp >> "mytap.dat", @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp | "gzip > mytap.dat.gz", @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp > stderr, @*, "index1", "index2"'
	 Example: mlr --from f.dat put '@sums[$a][$b]+=$x; emitp | "grep somepattern", @*, "index1", "index2"'

	 Please see http://johnkerl.org/miller/doc for more information.

   end
       end: defines a block of statements to be executed after input records
       are ingested. The body statements must be wrapped in curly braces.
       Example: 'end { emit @count }'
       Example: 'end { eprint "Final count is " . @count }'

   eprint
       eprint: prints expression immediately to stderr.
	 Example: mlr --from f.dat put -q 'eprint "The sum of x and y is ".($x+$y)'
	 Example: mlr --from f.dat put -q 'for (k, v in $*) { eprint k . " => " . v }'
	 Example: mlr --from f.dat put	'(NR % 1000 == 0) { eprint "Checkpoint ".NR}'

   eprintn
       eprintn: prints expression immediately to stderr, without trailing newline.
	 Example: mlr --from f.dat put -q 'eprintn "The sum of x and y is ".($x+$y); eprint ""'

   false
       false: the boolean literal value.

   filter
       filter: includes/excludes the record in the output record stream.

	 Example: mlr --from f.dat put 'filter (NR == 2 || $x > 5.4)'

	 Instead of put with 'filter false' you can simply use put -q.	The following
	 uses the input record to accumulate data but only prints the running sum
	 without printing the input record:

	 Example: mlr --from f.dat put -q '@running_sum += $x * $y; emit @running_sum'

   float
       float: declares a floating-point local variable in the current curly-braced scope.
       Type-checking happens at assignment: 'float x = 0' is an error.

   for
       for: defines a for-loop using one of three styles. The body statements must
       be wrapped in curly braces.
       For-loop over stream record:
	 Example:  'for (k, v in $*) { ... }'
       For-loop over out-of-stream variables:
	 Example: 'for (k, v in @counts) { ... }'
	 Example: 'for ((k1, k2), v in @counts) { ... }'
	 Example: 'for ((k1, k2, k3), v in @*) { ... }'
       C-style for-loop:
	 Example:  'for (var i = 0, var b = 1; i < 10; i += 1, b *= 2) { ... }'

   func
       func: used for defining a user-defined function.
       Example: 'func f(a,b) { return sqrt(a**2+b**2)} $d = f($x, $y)'

   if
       if: starts an if/elif/elif chain. The body statements must be wrapped
       in curly braces.

   in
       in: used in for-loops over stream records or out-of-stream variables.

   int
       int: declares an integer local variable in the current curly-braced scope.
       Type-checking happens at assignment: 'int x = 0.0' is an error.

   map
       map: declares an map-valued local variable in the current curly-braced scope.
       Type-checking happens at assignment: 'map b = 0' is an error. map b = {} is
       always OK. map b = a is OK or not depending on whether a is a map.

   num
       num: declares an int/float local variable in the current curly-braced scope.
       Type-checking happens at assignment: 'num b = true' is an error.

   print
       print: prints expression immediately to stdout.
	 Example: mlr --from f.dat put -q 'print "The sum of x and y is ".($x+$y)'
	 Example: mlr --from f.dat put -q 'for (k, v in $*) { print k . " => " . v }'
	 Example: mlr --from f.dat put	'(NR % 1000 == 0) { print > stderr, "Checkpoint ".NR}'

   printn
       printn: prints expression immediately to stdout, without trailing newline.
	 Example: mlr --from f.dat put -q 'printn "."; end { print "" }'

   return
       return: specifies the return value from a user-defined function.
       Omitted return statements (including via if-branches) result in an absent-null
       return value, which in turns results in a skipped assignment to an LHS.

   stderr
       stderr: Used for tee, emit, emitf, emitp, print, and dump in place of filename
	 to print to standard error.

   stdout
       stdout: Used for tee, emit, emitf, emitp, print, and dump in place of filename
	 to print to standard output.

   str
       str: declares a string local variable in the current curly-braced scope.
       Type-checking happens at assignment.

   subr
       subr: used for defining a subroutine.
       Example: 'subr s(k,v) { print k . " is " . v} call s("a", $a)'

   tee
       tee: prints the current record to specified file.
	 This is an immediate print to the specified file (except for pprint format
	 which of course waits until the end of the input stream to format all output).

	 The > and >> are for write and append, as in the shell, but (as with awk) the
	 file-overwrite for > is on first write, not per record. The | is for piping to
	 a process which will process the data. There will be one open file for each
	 distinct file name (for > and >>) or one subordinate process for each distinct
	 value of the piped-to command (for |). Output-formatting flags are taken from
	 the main command line.

	 You can use any of the output-format command-line flags, e.g. --ocsv, --ofs,
	 etc., to control the format of the output. See also mlr -h.

	 emit with redirect and tee with redirect are identical, except tee can only
	 output $*.

	 Example: mlr --from f.dat put 'tee >  "/tmp/data-".$a, $*'
	 Example: mlr --from f.dat put 'tee >> "/tmp/data-".$a.$b, $*'
	 Example: mlr --from f.dat put 'tee >  stderr, $*'
	 Example: mlr --from f.dat put -q 'tee | "tr [a-z\] [A-Z\]", $*'
	 Example: mlr --from f.dat put -q 'tee | "tr [a-z\] [A-Z\] > /tmp/data-".$a, $*'
	 Example: mlr --from f.dat put -q 'tee | "gzip > /tmp/data-".$a.".gz", $*'
	 Example: mlr --from f.dat put -q --ojson 'tee | "gzip > /tmp/data-".$a.".gz", $*'

   true
       true: the boolean literal value.

   unset
       unset: clears field(s) from the current record, or an out-of-stream or local variable.

	 Example: mlr --from f.dat put 'unset $x'
	 Example: mlr --from f.dat put 'unset $*'
	 Example: mlr --from f.dat put 'for (k, v in $*) { if (k =~ "a.*") { unset $[k] } }'
	 Example: mlr --from f.dat put '...; unset @sums'
	 Example: mlr --from f.dat put '...; unset @sums["green"]'
	 Example: mlr --from f.dat put '...; unset @*'

   var
       var: declares an untyped local variable in the current curly-braced scope.
       Examples: 'var a=1', 'var xyz=""'

   while
       while: introduces a while loop, or with "do", introduces a do-while loop.
       The body statements must be wrapped in curly braces.

   ENV
       ENV: access to environment variables by name, e.g. '$home = ENV["HOME"]'

   FILENAME
       FILENAME: evaluates to the name of the current file being processed.

   FILENUM
       FILENUM: evaluates to the number of the current file being processed,
       starting with 1.

   FNR
       FNR: evaluates to the number of the current record within the current file
       being processed, starting with 1. Resets at the start of each file.

   IFS
       IFS: evaluates to the input field separator from the command line.

   IPS
       IPS: evaluates to the input pair separator from the command line.

   IRS
       IRS: evaluates to the input record separator from the command line,
       or to LF or CRLF from the input data if in autodetect mode (which is
       the default).

   M_E
       M_E: the mathematical constant e.

   M_PI
       M_PI: the mathematical constant pi.

   NF
       NF: evaluates to the number of fields in the current record.

   NR
       NR: evaluates to the number of the current record over all files
       being processed, starting with 1. Does not reset at the start of each file.

   OFS
       OFS: evaluates to the output field separator from the command line.

   OPS
       OPS: evaluates to the output pair separator from the command line.

   ORS
       ORS: evaluates to the output record separator from the command line,
       or to LF or CRLF from the input data if in autodetect mode (which is
       the default).

AUTHOR
       Miller is written by John Kerl <kerl.john.r@gmail.com>.

       This manual page has been composed from Miller's help output by Eric
       MSP Veith <eveith@veith-m.de>.

SEE ALSO
       awk(1), sed(1), cut(1), join(1), sort(1), RFC 4180: Common Format and
       MIME Type for Comma-Separated Values (CSV) Files, the miller website
       http://johnkerl.org/miller/doc



				  2018-01-06			     MILLER(1)
