On 11/16/07, R (Chandra) Chandrasekhar <[EMAIL PROTECTED]> wrote:
> This is a Linux-oriented question.
Then why would you ask it in a Perl-oriented forum? It would seem,
from your opening, that you should be asking in a Linux-oriented
forum. (But you do have a Perl question, after all.)
> system "sudo -u \#$uid mkdir -m 755 $rootdir"; # (A)
What happens if you put this line above that one?
print "About to run: sudo -u \#$uid mkdir -m 755 $rootdir\n";
> system "sudo -u \\#$uid cp $fontdir/*.$fontdoc $paths{doc}"; # (B)
And this above that one:
print "About to run: sudo -u \\#$uid cp $fontdir/*.$fontdoc $paths{doc}\n";
> I have found that in bash or dash as the shell in Linux, I need to
> backslash the hash character # to give a numeric UID to sudo
> because the shell (like Perl) interprets # as a comment character.
> Strangely, I have found by trial and error that a single backslash-hash
> (\#) is needed for statement (A) to work but a double backslash-hash
> (\\#) is needed for statement (B) to work. Changing both to single or
> double backslashes results in error messages from the shell.
I admire someone who admits publicly to playing trial-and-error with
sudo. But it's not necessary in this case. If you tried the print
statements, you should have seen that "\#" means a hash mark, but
"\\#" means a backslash and a hash mark. A single backslash is the
same as none at all, in this case. If you want to give a literal
backslash to the shell, you have to use two backslashes in your source
code to mean one real one.
Statement A seems to be correct with one backslash (meaning none in
the command) because it works fine without any backslashes at all.
Because perl doesn't see any shell metacharacters in that command
(oddly, it seems that "#" doesn't count), it runs sudo directly; so
sudo is happy to get the hash mark. In contrast, when running
statement B, perl sees a shell metacharacter, so it has to call the
shell to handle it. The shell eats the backslash in that command, then
gives the hash mark to sudo.
But you don't really need the shell, do you? Since you're running
sudo, avoiding the shell is probably a good idea for security reasons,
too. You could give system() a list of arguments, and then there's no
shell involved; a simple hash mark will stay a hash mark:
system "sudo", "-u", "#$uid", "mkdir", "-m", "755", $rootdir;
This has the additional advantage that the shell won't become confused
by any shell metacharacters in $rootdir, should they creep in.
Hope this helps!
--Tom Phoenix
Stonehenge Perl Training
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
