library will handle this for you. Check out
L<perlipc/"Bidirectional Communication with Another Process">
+perl-5.6.x introduced a version of piped open that executes a process
+based on its command line arguments without relying on the shell. (Similar
+to the C<system(@LIST)> notation.) This is safer and faster than executing
+a single argument pipe-command, but does not allow special shell
+constructs. (It is also not supported on Microsoft Windows, Mac OS Classic
+or RISC OS.)
+
+Here's an example of C<open '-|'>, which prints a random Unix
+fortune cookie as uppercase:
+
+ my $collection = shift(@ARGV);
+ open my $fortune, '-|', 'fortune', $collection
+ or die "Could not find fortune - $!";
+ while (<$fortune>)
+ {
+ print uc($_);
+ }
+ close($fortune);
+
+And this C<open '|-'> pipes into lpr:
+
+ open my $printer, '|-', 'lpr', '-Plp1'
+ or die "can't run lpr: $!";
+ print {$printer} "stuff\n";
+ close($printer)
+ or die "can't close lpr: $!";
+
=head2 The Minus File
Again following the lead of the standard shell utilities, Perl's
open(SCREEN, "+> lkscreen")
|| die "can't open lkscreen: $!";
- open(LOGFILE, "+>> /var/log/applog"
+ open(LOGFILE, "+>> /var/log/applog")
|| die "can't open /var/log/applog: $!";
The first one won't create a new file, and the second one will always
$ myprogram file1 file2 file3
-Can have all its files opened and processed one at a time
+can have all its files opened and processed one at a time
using a construct no more complex than:
while (<>) {
name into pipes. For example, to autoprocess gzipped or compressed
files by decompressing them with I<gzip>:
- @ARGV = map { /^\.(gz|Z)$/ ? "gzip -dc $_ |" : $_ } @ARGV;
+ @ARGV = map { /\.(gz|Z)$/ ? "gzip -dc $_ |" : $_ } @ARGV;
Or, if you have the I<GET> program installed from LWP,
you can fetch URLs before processing them:
"&" but rather with a "&=" combination, then Perl will not create a
completely new descriptor opened to the same place using the dup(2)
system call. Instead, it will just make something of an alias to the
-existing one using the fdopen(3S) library call This is slightly more
+existing one using the fdopen(3S) library call. This is slightly more
parsimonious of systems resources, although this is less a concern
these days. Here's an example of that:
C<< '<' >>, C<< '>' >>, C<< '>>' >>, C<< '|' >> and their variants,
for example:
- open(my $fh, "<:utf8", $fn);
+ open(my $fh, "<:crlf", $fn);
=item *