Hi On Mon, Oct 08, 2012 at 09:29:42PM +0100, Regid Ichira wrote: > I am a perl beginner. I stambled upon a perl line > > if (system("command -v wget >/dev/null 2>&1") == 0) > > I was able to find perl's documentation for system. But where is > the documentation for command?
"command" is a shell built-in command - so you should find it in the documentation for your shell - e.g. "man sh" should get you to the right manual page. Exactly *which* shell this is, depends on your system, but it is most likely "bash" or "dash" which provides /bin/sh. Searching for the string "command" in the manual page is bound to give LOTs of hits - try searching for "BUILTINS" instead - once you get to the list of built-in commands, you should find them in asciibetical order. > Am I right that that line tests whether wget is installed in the > system? How does it do that? It checks whether the "wget" command is available in $PATH, yes. So this can be fooled if you have $HOME/bin in your $PATH and you create your own shell script named "wget". The "> /dev/null 2>&1" has the effect of supressing any output to stdout and stderr, thus making the command silent regardless of whether it succeeds or fails. Hope this helps -- Karl E. Jorgensen -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20121008215827.GA13226@hawking