Re: [PATCH v2] Remove useless uses of cat, and replace with filename arguments or redirection

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Jun 7, 2007, 04:06 UTC
Message-ID: <Pine.LNX.4.64.0706070506230.4046@racer.site>
In-Reply-To: <46676C35.60406@freedesktop.org>

Hi,

On Wed, 6 Jun 2007, Josh Triplett wrote:

Show 29 quoted lines

> Junio C Hamano wrote:
> > Josh Triplett <josh@freedesktop.org> writes:
> >> Replace all uses of cat that do nothing other than read a single file.  In the
> >> case of git-quilt-import, this occurs once per patch.
> >>
> >> Signed-off-by: Josh Triplett <josh@freedesktop.org>
> >> ---
> >>
> >> This revised version fixes a bug caught by Stephen Rothwell: the output of wc
> >> -l changes when it has a filename on the command line.  The same bug occurred
> >> in one other place as well.
> > 
> > Hmph...
> > 
> >> diff --git a/git-filter-branch.sh b/git-filter-branch.sh
> >> index 0c8a7df..346cf3f 100644
> >> --- a/git-filter-branch.sh
> >> +++ b/git-filter-branch.sh
> >> @@ -333,7 +333,7 @@ for commit in $unchanged; do
> >>  done
> >>  
> >>  git-rev-list --reverse --topo-order $srcbranch --not $unchanged >../revs
> >> -commits=$(cat ../revs | wc -l | tr -d " ")
> >> +commits=$(wc -l ../revs | tr -d -c 0-9)
> > 
> > ... and left unfixed ;-)?
> 
> No, just fixed differently. :) Note the change to the tr invocation: delete
> everything other than digits.

Actually, it feels wrong. For example, if some wc some day decides to display the size in kilobyte, even if you say "-l", it would fail badly. That is, it would fail to function properly, but would not tell you that it failed.

Things like that are known to happen, and that's why "wc -l < file" is a better fix than "wc -l file | tr -dc 0-9". In this case, it might not matter for a long time, but why not stop being sloppy here and now?

Ciao, Dscho