columns

Purpose

I love this script so much! I must use this at least an average of once a day! The basic idea is that you tell it the positional columns you want to print and it prints them out.

Syntax

columns [-h] [-s DELIM | -r REGEXP | -c] [-n] [-f FILENAME] [-v] column [column ...]

Options and arguments

Option	Description	Default
-s DELIM or -F DELIM or --separator DELIM or --delim DELIM	Specifies the regular expression to separate columns.	The default is to separate columns by one or more whitespace characters
-r REGEXP or --regexp REGEXP	Specifies a regular expression by which to break up tokens	The default is to separate columns by one or more whitespace characters
-c or --csv	Reads input as CSV	The default is to separate columns by one or more whitespace characters
-n or --negate	Excludes specified columns	Includes specified columns
-f FILENAME or --filename FILENAME	Reads input from the specified file	The default is to read from stdin
-v or --verbose	Enables debugging messages	Debugging messages are not printed

You can can specify columns in a few ways:

• a single integer, the first column is 1
• two integers separated by a hyphen - 1-3 is synonymous with 1 2 3
• a single negative integer counts columns backwards - -1 is the last column </p>

  Be aware that if the first column you specify is negative, you'll likely have to use a trick to make it so that the script will not think that -1 is an option:

  $ columns -- -1
  

  This is a common technique when invoking Unix commands so it's handy to remember!
  </ul>

  Example

  $ ls -l
  total 0
  -rw-rw-r-- 1 bruno bruno 0 Aug 14 12:44 1
  -r--r--r-- 1 bruno bruno 0 Aug 14 12:44 2
  -rw-rw-r-- 1 bruno bruno 0 Aug 14 12:44 3
  -rwxrwxr-x 1 bruno bruno 0 Aug 14 12:44 foobar.txt
  $ ls -l | columns 1 -1
  total 0
  -rw-rw-r-- 1
  -r--r--r-- 2
  -rw-rw-r-- 3
  -rwxrwxr-x foobar.txt
  $
  

  Notes

  • The data is read from stdin. If stdin is not directed from a file or pipe, en error message is printed and the script terminates
  • Negative columns don't work when `--negate` is specified and no error is thrown.