— expand tabs to spaces, and
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.
unexpand puts tabs back into the data from
the standard input or the named files and writes the result on the standard
The options are as follows:
- By default, only leading blanks and tabs are reconverted to maximal
strings of tabs. If the
-aoption is given, tabs are inserted whenever they would compress the resultant file by replacing two or more characters.
- If the argument to
-t, tablist, consists of a single numerical argument, tabs are set tablist spaces apart instead of the default 8. If multiple
-toptions are given, then the tabs are set at those specific columns.
Otherwise the argument to
-tmay consist of a list of two or more positive decimal integers, separated by commas or single blank characters, in ascending order: in the event of having to process a ⟨tab⟩ at a position beyond the last of those specified in a multiple
-tlist, the ⟨tab⟩ is replaced by a single ⟨space⟩ character.
This implementation of
expandadditionally allows tablist to be specified without using the
-tflag, by prefixing tablist with a dash (-).
unexpand utilities exit 0 on success,
and >0 if an error occurs.
unexpand utilities are compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
specification, except that this implementation does not support a
-t flag for
The ability to specify tabstops without the
-t flag is not specified by IEEE
Std 1003.1-2008 (“POSIX.1”), though it states it
“may be present in some implementations”.
expand utility first appeared in