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[ find-grep-dired ] Regexp input and other remarks

From: Fabrice Bauzac
Subject: [ find-grep-dired ] Regexp input and other remarks
Date: Sat, 02 Mar 2002 20:02:50 +0100

Good evening everyone,

I used the find-grep-dired command to search for files matching a
regular expression.  My regular expression was simple: it was the
string `2.4.12'.  Since find-grep asked for a regexp:

Find-grep (grep regexp):

I entered: 


so that the dots aren't interpreted by grep as the all-matching
character.  But the commandline sent to the shell seems to not quote
special characters, because here is the result of find-grep:

  find . \( -type f -exec grep -q 2\.4\.12 {} \;  \) -exec ls -ld {} \;
  -rw-r--r--    1 noon     noon       359166 mar  7  2001 

The files don't contain the _string_ `2.4.12' (at least, not the first
file).  But the first file contains strings such as `254,128' which
match the regexp /2.4.12/.

Moreover, if the user inserts an unquoted space, `grep' recieves
several arguments, and that isn't a proper behaviour.  If the user
inserts the string {}, or if there is a leading dash (which will be
interpreted as the start of a switch by grep), too.  In fact there are
quite many situations where one can't just put a normal regular
expression at the find-grep prompt.

One workaround would be to quote the regexp with single quotes '' at
the `Find-grep (grep regexp):' prompt.

But I think it would be more user-friendly if it was GNU Emacs that quoted
the user's string:

* Replace every _'_ with _'\''_

* Put an initial and a final quote _'_

* Use -q -e as arguments to `grep' instead of just -q, in order to
  prevent the "leading dash" interpretation.

But if GNU Emacs does that, there are possible problems, including:

* No compatibility with previous GNU Emacs versions (but it is
  possible to use another name for the modified command, thus leaving
  find-grep with its current behaviour).

* Maybe shell dependance (I don't know the UNIX shells that are not
  Bourne: maybe the character _'_ does not have the same
  meaning/behaviour).  Maybe Emacs could explicitely run /bin/sh.

* Maybe dependance for the version of grep concerning the -e switch
  (i.e. I don't know whether all the grep programs understand the
  meaning of that switch).

Maybe this has been previously discussed?  Sorry if it is the case.

Have a nice weekend.

fabrice bauzac
Software should be free.  http://www.gnu.org/philosophy/why-free.html

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