How to execute tar inside a perl script ?

[Matthew Lincoln]

When I code in a perl script

tar czvf "/usr/local/myname/$tarfile" ./*.php

I got the following error:

Search pattern not terminated at /usr/local/myname/bin/myscript.pl line 20.

If I code:

tar czvf "/usr/local/myname/$tarfile" ./*.php ./templates/

then I got this error:

Quantifier follows nothing in regex; marked by <-- HERE in m/* <-- HERE .php ./ at /usr/local/myname/bin/myscript.pl line 20.

So how do I correctly execute a tar command from within a perl script ?

Matthew

 

[Joost Diepenmaat]

When I code in a perl script

tar czvf "/usr/local/myname/$tarfile" ./*.php

perl isn't a shell. tar isn't a perl function. czvf can be all kinds of
things in perl. If you want to execute an external commmand and
interpolate wildcards via the shell you have to explicitly say so.

So how do I correctly execute a tar command from within a perl script ?

http://perldoc.perl.org/functions/system.html

Joost.

 

[Joost Diepenmaat]

This is a correct, but it's prob worth expanding on this slightly to get
you going, from within your code, try the following:

my $tar_cmd = "tar czvf "/usr/local/myname/$tarfile" ./*.php" ;

That's not valid perl. You probably mean

my $tar_cmd = "tar czvf /usr/local/myname/$tarfile ./*.php" ;

Joost.

 

[Ben Morrow]

That's not valid perl. You probably mean

my $tar_cmd = "tar czvf /usr/local/myname/$tarfile ./*.php" ;

No, he probably meant

my $tar_cmd = qq{tar czvf "/usr/local/myname/$tarfile" ./*.php};

as the "" are important. It would be *much* better to use the list form
of system: it avoids all these nasty quoting issues, including the one
you haven't noticed yet when you have a file 'My Script.php'.

system tar => czvf => "/usr/local/myname/$tarfile", <*.php>;

(handling the return value left as an exercise for the reader, as it's a
pain .)

Ben

 

[Joost Diepenmaat]

No, he probably meant

my $tar_cmd = qq{tar czvf "/usr/local/myname/$tarfile" ./*.php};

Which won't work, because it won't interpolate ./*.php. Which sort of
proves both our points

as the "" are important. It would be *much* better to use the list form
of system: it avoids all these nasty quoting issues, including the one
you haven't noticed yet when you have a file 'My Script.php'.

system tar => czvf => "/usr/local/myname/$tarfile", <*.php>;

Yes, that would work, and more reliably than all the crap above. (though
I don't like => to quote strings except in very idiomatic constructs).

Joost.

 

[Ben Morrow]

Which won't work, because it won't interpolate ./*.php. Which sort of
proves both our points

Yes it will. That is, ./*.php will be passed literally to the shell,
which will then expand it before calling tar. This is why $tarfile needs
two levels of quoting, with qq{} (for Perl) and "" (for the shell).

Ben

 

[Joost Diepenmaat]

Which won't work, because it won't interpolate ./*.php. Which sort of
proves both our points

Scratch that. ofcourse it will work.

Joost.

 

[Josef Moellers]

Yes it will. That is, ./*.php will be passed literally to the shell,
which will then expand it before calling tar. This is why $tarfile needs
two levels of quoting, with qq{} (for Perl) and "" (for the shell).

(Stomping the ground with the foot) No it won't:

The list form of system will bypass the shell:
josef@bounty:/usr/lib> perl
system("ls", "*");
ls: *: No such file or directory

Hence, no expansion will take place.

Josef

 

[Martijn Lievaart]

(Stomping the ground with the foot) No it won't:

The list form of system will bypass the shell: josef@bounty:/usr/lib>
perl
system("ls", "*");
ls: *: No such file or directory

Hence, no expansion will take place.

It's no list, it's a single string with wildcard characters, hence it
will be passed to the shell and it will be expanded.

# perl -e 'system qq{ls *}'
<snip listing of files>

M4

 

[Josef Moellers]

It's no list, it's a single string with wildcard characters, hence it
will be passed to the shell and it will be expanded.

# perl -e 'system qq{ls *}'
<snip listing of files>

Sorry, you're right, I mixed up both examples in Ben's reply and didn't
notice the globbing operator in this section:

It would be *much* better to use the list form
of system: it avoids all these nasty quoting issues, including the one
you haven't noticed yet when you have a file 'My Script.php'.

system tar => czvf => "/usr/local/myname/$tarfile", <*.php>;