A simple script to tabulate data within a Unix pipeline into an ASCII-art table,
optionally filtering the data, taking only certain columns, etc.

A rather contrived example:

[davidp@supernova:~]$ ps ax
  PID TTY      STAT   TIME COMMAND
    1 ?        Ss     0:09 init [2]  
    2 ?        S<     0:00 [kthreadd]
    3 ?        S<     0:00 [migration/0]
    4 ?        S<     2:35 [ksoftirqd/0]
    5 ?        S<     0:00 [watchdog/0]

Let's say I want that in a table, only want the first and last column, and only want processes with 'ssh in the name:

[davidp@supernova:~]$ ps ax | ./tabulate -f 0,4, --filter ssh -K 1
|13345|/usr/sbin/sshd|
|15036|sshd:         |
|15038|sshd:         |
|15660|sshd:         |
|15662|sshd:         |


TODO: document properly :)

Options taken:

--fieldspec / -f
    List the columns you want.  Note - indexing starts at 0.
    Examples: 0,3 - first and third.  0..3 - first four columns.  

--headers / -h
    Specify column heading names

--filter / -m
    Include only rows which match the given pattern

--skip-first / --skipfirst / -s
    Skip the first X rows.  Example: --skip-first=1

--keep-first / --keepfirst / -K
    Do not discard the first X rows.  Only useful when using --filter.

--separator / --seperator / --sep
    Character to use to separate columns in output.  Defaults to '|'.

--split-on / --spliton
    Pattern to use to split input into columns.  Default: '\s+' (whitespace)