NAME
expand, unexpand - expand tabs to spaces, and vice versa

SYNOPSIS
expand [ -tabstop ] [ -tab1,tab2,...,tabn ] [ file ... ]
unexpand [ -a ] [ file ... ]

DESCRIPTION
Expand processes the named files or the standard input writing the
standard output with tabs changed into blanks. Backspace
characters are preserved into the output and decrement the column
count for tab calculations. Expand is useful for pre-processing
character files (before sorting, looking at specific columns, etc.)
that contain tabs.

If a single tabstop argument is given, then tabs are set tabstop
spaces apart instead of the default 8. If multiple tabstops are
given then the tabs are set at those specific columns.

Unexpand puts tabs back into the data from the standard input or
the named files and writes the result on the standard output. By
default, only leading blanks and tabs are reconverted to maximal
strings of tabs. If the -a option is given, then tabs are inserted
whenever they would compress the resultant file by replacing two or
more characters.