File: grep.info,  Node: General Output Control,  Next: Output Line Prefix Control,  Prev: Matching Control,  Up: Command-line Options

2.1.3 General Output Control
----------------------------

‘-c’
‘--count’
     Suppress normal output; instead print a count of matching lines for
     each input file.  With the ‘-v’ (‘--invert-match’) option, count
     non-matching lines.  (‘-c’ is specified by POSIX.)

‘--color[=WHEN]’
‘--colour[=WHEN]’
     Surround matched non-empty strings, matching lines, context lines,
     file names, line numbers, byte offsets, and separators (for fields
     and groups of context lines) with escape sequences to display them
     in color on the terminal.  The colors are defined by the
     environment variable ‘GREP_COLORS’ and default to
     ‘ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36’ for bold red
     matched text, magenta file names, green line numbers, green byte
     offsets, cyan separators, and default terminal colors otherwise.
     *Note Environment Variables::.

     WHEN is ‘always’ to use colors, ‘never’ to not use colors, or
     ‘auto’ to use colors if standard output is associated with a
     terminal device and the ‘TERM’ environment variable's value
     suggests that the terminal supports colors.  Plain ‘--color’ is
     treated like ‘--color=auto’; if no ‘--color’ option is given, the
     default is ‘--color=never’.

‘-L’
‘--files-without-match’
     Suppress normal output; instead print the name of each input file
     from which no output would normally have been printed.

‘-l’
‘--files-with-matches’
     Suppress normal output; instead print the name of each input file
     from which output would normally have been printed.  Scanning each
     input file stops upon first match.  (‘-l’ is specified by POSIX.)

‘-m NUM’
‘--max-count=NUM’
     Stop after the first NUM selected lines.  If NUM is zero, ‘grep’
     stops right away without reading input.  A NUM of −1 is treated as
     infinity and ‘grep’ does not stop; this is the default.

     If the input is standard input from a regular file, and NUM
     selected lines are output, ‘grep’ ensures that the standard input
     is positioned just after the last selected line before exiting,
     regardless of the presence of trailing context lines.  This enables
     a calling process to resume a search.  For example, the following
     shell script makes use of it:

          while grep -m 1 'PATTERN'
          do
            echo xxxx
          done < FILE

     But the following probably will not work because a pipe is not a
     regular file:

          # This probably will not work.
          cat FILE |
          while grep -m 1 'PATTERN'
          do
            echo xxxx
          done

     When ‘grep’ stops after NUM selected lines, it outputs any trailing
     context lines.  When the ‘-c’ or ‘--count’ option is also used,
     ‘grep’ does not output a count greater than NUM.  When the ‘-v’ or
     ‘--invert-match’ option is also used, ‘grep’ stops after outputting
     NUM non-matching lines.

‘-o’
‘--only-matching’
     Print only the matched non-empty parts of matching lines, with each
     such part on a separate output line.  Output lines use the same
     delimiters as input, and delimiters are null bytes if ‘-z’
     (‘--null-data’) is also used (*note Other Options::).

‘-q’
‘--quiet’
‘--silent’
     Quiet; do not write anything to standard output.  Exit immediately
     with zero status if any match is found, even if an error was
     detected.  Also see the ‘-s’ or ‘--no-messages’ option.
     Portability note: Solaris 10 ‘grep’ lacks ‘-q’; portable shell
     scripts typically can redirect standard output to ‘/dev/null’
     instead of using ‘-q’.  (‘-q’ is specified by POSIX.)

‘-s’
‘--no-messages’
     Suppress error messages about nonexistent or unreadable files.
     (‘-s’ is specified by POSIX.)