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I want to get the explanation for ! option (which means exclude) in find command in the man find.

And then I press / and shift + 1 , a Non-match popped out, instead of ! So my question is how to search for ! in a manpage?


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up vote 14 down vote accepted

The default man pager is less. If you look at less's help (press h while in it), you'll see:


  /pattern          *  Search forward for (N-th) matching line.
  ?pattern          *  Search backward for (N-th) matching line.
  n                 *  Repeat previous search (for N-th occurrence).
  N                 *  Repeat previous search in reverse direction.
  ESC-n             *  Repeat previous search, spanning files.
  ESC-N             *  Repeat previous search, reverse dir. & spanning files.
  ESC-u                Undo (toggle) search highlighting.
  &pattern          *  Display only matching lines
        A search pattern may be preceded by one or more of:
        ^N or !  Search for NON-matching lines.

Or in man less:

      Search forward in the file for the N-th line containing the pat‐
      tern.  N defaults to 1.  The pattern is a regular expression, as
      recognized  by  the  regular expression library supplied by your
      system.  The search starts at the first line displayed (but  see
      the -a and -j options, which change this).

      Certain  characters  are  special if entered at the beginning of
      the pattern; they modify the type of search rather  than  become
      part of the pattern:

      ^N or !
             Search for lines which do NOT match the pattern.

So, a pattern of just ! is an empty pattern (which matches anything) negated - so nothing will match it.

You'll have to escape the significance of ! at the start of a pattern, by either using a backslash (\!), or otherwise making it not the first character of the regex (/[!], for example).

The other way is to use grep:

$ man find | grep !
       with  `-', or the argument `(' or `!'.  That argument and any following
       ! expr True  if  expr  is false.  This character will also usually need
              Same as ! expr, but not POSIX compliant.
       The POSIX standard specifies parentheses `(', `)', negation `!' and the
       find /sbin /usr/sbin -executable \! -readable -print
       find . -perm -444 -perm /222 ! -perm /111
       find . -perm -a+r -perm /a+w ! -perm /a+x
       -perm  /222 or -perm /a+w) but are not executable for anybody ( ! -perm
       /111 and ! -perm /a+x respectively).
       find . -name .snapshot -prune -o \( \! -name *~ -print0 \)|
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You need to type \ before you type !, so that it will not be interpreted as a negation regular expression in search.

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Another way to do this:

man -html=firefox find

After the manpage opens in firefox, press CTRL + F to search for any character.

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That's --html or -H. – Boris the Spider Feb 4 at 11:15

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