First post, file handle question

happyperl has asked for the wisdom of the Perl Monks concerning the following question:

Guys, I have read some code that I don't quite understand, especially what the expression below on opening files.

open (SKEL, "cat " . join (" ", @ARGV) . " |") || die "Could not open 
+$ARGV[0].\n$usage";
[download]

I have trouble understanding what the it does, especially: "cat " . join (" ", @ARGV) . " |" Could you give me some hints? Thanks!

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Re: First post, file handle question by MidLifeXis (Monsignor) on Apr 17, 2013 at 17:21 UTC
It is opening a pipe to read the output of the unix cat command followed by the parameters passed on the command line, joined by a space. So if you do `myscript foo bar`, it will read the output from the unix-like command `cat foo bar` and process it. Be aware that this is not the best way to do this. If I were to pass the following arguments `/dev/null; echo rm -rf /; echo Gotcha!` (but properly quoted and removing the first echo), your application would do much more than you wanted it to do. It would run the set of unix commands `cat /dev/null; echo rm -rf /; echo Gotcha` and give you the output from that (again, remove the echo from the rm command). --MidLifeXis	[reply] [d/l] [select]
Re^2: First post, file handle question by Anonymous Monk on Apr 17, 2013 at 19:35 UTC
See also: Bobby Tables	[reply]
Re^2: First post, file handle question by happyperl (Initiate) on Apr 17, 2013 at 19:38 UTC
So instead of putting all the command line argument files into a single file before going into this perl script, this lines execute the cat command inside a perl? I got that.	[reply]
Re: First post, file handle question by AnomalousMonk (Archbishop) on Apr 18, 2013 at 11:23 UTC
open (SKEL, "cat " . join (" ", @ARGV) . " \|") \|\| die "Could not open $ARGV[0].\n$usage"; Just a picky parenthetic note: If the special variable `$"` retains its default value of a single space (see perlvar), the expression `"cat " . join (" ", @ARGV) . " \|"` is exactly equivalent to the much shorter and clearer expression `"cat @ARGV \|"` which, for some reason, the original author did not want (or know how) to use.	[reply] [d/l] [select]