script perl with sed command

[Giorgos Keramidas]

On 2007-04-07 17:31, Olivier Regnier <oregnier at steelbox.org> wrote:
> Hello,
> I have a problem with my perl script with the command sed. Here is a
> example of my code:

Don't use system("sed ...") in Perl.  It's considered poor style, since
Perl can do the same without having to fork a shell/sed process.

> # Selecting the fast server
> print "Using the server called $server";
> system(`/usr/bin/sed 's|\*default host=\(.*\)|\*default host=${server}|' 
> $standard_supfile > $standard_supfile.copy`);
> system('/bin/mv $standard_supfile.copy $standard_supfile');

Try using Perl only, instead of forking sed(1), like this:

,-----------------------------------------------------------------------
|
| #!/usr/bin/perl -Tw
|
| use strict;
|
| #
| # supfile_set_default_host($supfile, $newhost)
| #       Set the default host used by the supfile $supfile to the
| #       host name supplied as $newhost.
| #
|
| sub supfile_set_default_host($$);
| sub supfile_set_default_host($$)
| {
|     my $tmpsupfile;
|     my $supfile = shift;
|     my $newhost = shift;
|
|     if (!defined($supfile) || !defined($newhost)) {
|         return undef;
|     }
|
|     $tmpsupfile = "tmp-" . $supfile;
|     open(SUP, "$supfile") or die "$!";
|     open(TMP, "> $tmpsupfile") or die "$!";
|
|     my $line;
|     while (defined($line = <SUP>)) {
|         chomp $line;
|         $line =~ s/^(\*[ \t]*default[ \t][ \t]*host[ \t]*=).*/$1${newhost}/;
|         print TMP "$line\n";
|     }
|     close(TMP) or die "$!";
|     close(SUP) or die "$!";
|     rename("$tmpsupfile", "$supfile") or die "$!";
|     return 1;
| }
|
| supfile_set_default_host('standard-supfile', 'cvsup.example.net');
|
`-----------------------------------------------------------------------

This is slightly more complex than forking a sed(1) utility run, but
it's easier to understand (at least it is for me).

A very brief run of the script seems to work here:

,-----------------------------------------------------------------------
|
| $ pwd
| /tmp
| $ cp /usr/share/examples/cvsup/standard-supfile .
| $ grep 'default host' standard-supfile
| *default host=CHANGE_THIS.FreeBSD.org
| $ perl -Tw supfile.pl
| $ grep 'default host' standard-supfile
| *default host=cvsup.keramida
| $
|
`-----------------------------------------------------------------------

- Giorgos