NAME jawk -- like awk, but post-modern and perly. AKA, Josh's Awk. SYNOPSIS jawk [-x] [-e 'code'] [-d delim] fieldspec [fieldspec...] [-- (FILES..)]: If you haven't seen awk, then jawk can be described as a flexible tool for extracting columns of data from text files. If you've seen 'awk', then we can describe jawk as a replacement for statements like awk '{print $N}' which supports ranges, indexing columns by negative numbers, a perl mode, and more. DESCRIPTION jawk 1 is somewhat like awk '{print $1}'. Let's start with a fairly complex example. Suppose you have a file called 'users.txt' with lines of data in this format: Bob Elmer, 2716 Fremont Blvd, New York, NY, 12344, ID:91818, CanastaRating:3.1415 Elmer Fudd, 1 Bunny Hill Drive, Tarrytown, NY, 87654, ID:1, CanastaRating:123456789 This statement would pull out the 1st, and 3rd through last columns, using ', ' as an input delimiter (we've put two spaces between options, for clarity): jawk -d', ' 1 3..-1 -- users.txt Note the use of negative indexes, the non-default element delimiter via `-d', and the `--' anti-option (which indicates that following arguments should be considered files to read). jawk also allows ranges using the `..' sequence. For example, a field specification can look like `A', `A..B', `A..', or `..B', where (`A' and `B' can be negative or positive integers. Negative values for A and B count backwards, so -1 is the last field. Use -- or - FILENAME.txt to read from files. '--' is needed to treat FILENAME.txt as file and not fieldspec. See examples below. Where you might previously use a command like grep pattern file.txt | awk '{print $2}' to pull out the 2nd column from a file, you can now do: grep pattern file.txt | jawk 2 jawk offers many other improvements. Here are examples: select out the 1st, 3rd, and 4th columns from file cat file | jawk 1 3 4 select all columns except the 1st, and 9th through remaining. Uses the -x option for an 'except' meaning. cat file | jawk -x 1 9..-1 select out the first through third, and the second to last, and last cols from a file. cat file | jawk 1..3 -2 -1 Same as above, but using : as an input delimiter instead of whitespace. Note use of -- to start list of files to read from @ARGV, so we can pass `file' to jawk directly instead of through `cat'. jawk -d: 1..3 -2 -1 -- file There is also a -exe='perlcode' mode where you access the args via @F, and not via named positional args. Like so: cat file | jawk -e 'print "@F\n";' OPTIONS Here's an explation of all the command-line options: `NON-ZERO INTEGER' A field specification option indicating that this particular column should (or should not, depending on -x, be output). Negative indexes count from the right, like in perl, so the right-most column is number `-1'. `RANGE OF NON-ZERO INTEGERS' Integer ranges are specified with `..', and given that A and B are non-zero integers, can look like A..B A.. ..B If you specify ranges in reverse order from their source, like `cat file | jawk -1..1' or `cat file | jawk 8-2' you'll get the fields in reverse order, like you asked. -d delimiter (or -d=delimiter) Specify an alternate delimiter in place of '\s+'. If not ' ', the delimiter is processed through perl's quotemeta() function and used as a regular expression to match between input fields. -j joiner (or -j=joiner) Specify an alternate join character sequence in place of 'space'. -x Exclude the chosen columns, negating their meaning. Does not interoperate with -e 'perlcode' option. -e='perlcode' or -e 'perlcode' Use perl code passed to process parsed items. Fields come in through the @F array, and are 0-indexed (like in perl) instead of 1-indexed (like in jawk and cut). A simple example, which shows the first and second columns of input, is cat file.txt | jawk -e 'print "$F[0] $F[1]\n"' -w Run perl code used with -e option with warnings on. (Strictness is always enabled but can be disabled by putting 'no strict' in your script). -- Ends argument parsing. Used to pass filenames to read from stdin. See examples above. BUGS None known COPYRIGHT Copyright (c) 2011 Josh Rabinowitz, All Rights Reserved. AUTHORS Josh Rabinowitz