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From: martin%easby.durham.ac.uk@pucc.PRINCETON.EDU (Martin Ward)
Newsgroups: comp.lang.perl
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Message-ID: <1990Jul10.095016.2473@uvaarpa.Virginia.EDU>
Date: 10 Jul 90 09:50:16 GMT
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The perl man page suggests that the following are equivalent:

                  open(FOO, "cat -n $file|");
                  open(FOO, "-|") || exec 'cat', '-n', $file;

But this is not the case if $file contains whitespace or metacharacters.
The first line will pass "cat -n $file" to the sh which will expand
metacharacters and extract arguments to pass to cat, the second line
passes the two arguments "-n" and "$file" directly to cat. Perusal of the
section on exec suggests that:

                  open(FOO, "-|") || exec "cat -n $file";

is truly equivalent to open(FOO, "cat -n $file|"); in that exec with one
argument either extracts the arguments separated by white space in the string
or (if the string contains metacharacters) passes the string to sh for
argument extraction and filename globbing.

If you don't want gratuitous globbing then the version:

                  open(FOO, "-|") || exec 'cat', '-n', $file;

is to be preferred (eg if $file came from @ARGV).

			Martin.

My ARPANET address is:  martin%EASBY.DUR.AC.UK@CUNYVM.CUNY.EDU
OR: martin%uk.ac.dur.easby@nfsnet-relay.ac.uk  UUCP:...!mcvax!ukc!easby!martin
JANET: martin@uk.ac.dur.easby    BITNET: IN%"MARTIN@EASBY.DURHAM.AC.UK"