EXPAND(1) OpenBSD Reference Manual EXPAND(1)
expand, unexpand - expand tabs to spaces, and vice versa
expand [-tabstop] [-tab1,tab2,...,tabn] [file ...]
expand [-t tabstop] [-t tab1,tab2,...,tabn] [file ...]
unexpand [-a] [file ...]
expand processes the named files or the standard input, writing the stan-
dard output with tabs changed into blanks. Backspace characters are pre-
served into the output and decrement the column count for tab calcula-
tions. expand is useful for pre-processing character files (before sort-
ing, looking at specific columns, etc.) that contain tabs.
If a single tabstop argument is given, 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. In the synopsis above, both forms of
the expand command are identical.
If a list of tabstops is given, it should consist of a list of two or
more positive decimal integers, in ascending order. In the event of hav-
ing to process a <tab> at a position beyond the last of those specified
in a multiple tabstop list, the <tab> is replaced by a single <space>
unexpand puts tabs back into the data from the standard input or the
named files and writes the result on the standard output.
The options (for unexpand only) are as follows:
-a By default, only leading blanks and tabs are reconverted to maximal
strings of tabs. If the -a option is given, tabs are inserted
whenever they would compress the resultant file by replacing two or
The expand and unexpand utilities are compliant with the IEEE Std 1003.1
(``POSIX'') specification, with the following exceptions:
o POSIX does not support specifying tabstops without use of the
-t flag (first form in SYNOPSIS above).
o POSIX specifies that multiple tabstops may be given separated
by commas or blanks. This implementation supports only comma-
o unexpand does not recognise the -t flag.
The expand command appeared in 3.0BSD.
OpenBSD 3.6 June 9, 1993 1