unexpand

Convert spaces to tabs, write the contents of each given FILE, or standard input if none are given or for a FILE of `-', to standard output. Strings of two or more space or tab characters are converted to as many tabs as possible followed by as many spaces as are needed.

SYNTAX
      unexpand [OPTION]... [FILE]...

OPTIONS

`-TAB1[,TAB2]...'
`-t TAB1[,TAB2]...'
`--tabs=TAB1[,TAB2]...'
     If only one tab stop is given, set the tabs TAB1 spaces apart
     instead of the default 8.  Otherwise, set the tabs at columns
     TAB1, TAB2, ... (numbered from 0), and leave spaces and tabs
     beyond the tabstops given unchanged.  If the tabstops are specified
     with the `-t' or `--tabs' option, they can be separated by blanks
     as well as by commas.  This option implies the `-a' option.

`-a'
`--all'
     Convert all strings of two or more spaces or tabs, not just initial
     ones, to tabs.

By default, `unexpand' converts only initial spaces and tabs (those that precede all non space or tab characters) on each line.
It preserves backspace characters in the output; they decrement the column count for tab calculations.
By default, tabs are set at every 8th column.

Related commands:

cut - Divide a file into several parts
expand - Convert tabs to spaces
expr - Evaluate expressions
fmt - Reformat paragraph text
grep - Search file(s) for lines that match a given pattern
seq - Print numeric sequences
tr - Translate, squeeze, and/or delete characters
uuencode - Encode a binary file

Equivalent Windows NT commands:

MUNGE - Find and Replace text within file(s)