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NAME

expand, unexpand — expand tabs to spaces, and vice versa

SYNOPSIS

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.

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 are as follows:

-a

(unexpand only) 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 more characters.

-t tablist

(expand only) 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 -t options are given, then the tabs are set at those specific columns.

Otherwise the argument to -t may consist of a list of two or more positive decimal integers, comma separated, in ascending order: in the event of having to process a ⟨tab⟩ at a position beyond the last of those specified in a multiple -t list, the ⟨tab⟩ is replaced by a single ⟨space⟩ character.

This implementation of expand additionally allows tablist to be specified without using the -t flag, by prefixing tablist with a dash (-).

EXIT STATUS

The expand and unexpand utilities exit 0 on success or >0 if an error occurred.

SEE ALSO

fold(1)

STANDARDS

The expand and unexpand utilities are compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification, with the following exceptions:

• POSIX does not support specifying tabstops without use of the -t flag.
• POSIX specifies that multiple tabstops may be given separated by commas or blanks. This implementation supports only comma-separated tabstops.
• unexpand does not recognise the -t flag.

HISTORY

The expand utility first appeared in 1BSD.