Re: [PATCH] [doc] be more explicit about magic argv

Message-ID: <20081030182902.25398.qmail@lists.develooper.com>

p4raw-id: //depot/perl@34670

2 files changed, 16 insertions, 0 deletions

diff --git a/pod/perlop.pod b/pod/perlop.pod
index 7b0b0d2294..f52f79f5be 100644
--- a/pod/perlop.pod
+++ b/pod/perlop.pod
@@ -2246,6 +2246,18 @@ internally--<> is just a synonym for <ARGV>, which
 is magical.  (The pseudo code above doesn't work because it treats
 <ARGV> as non-magical.)
 
+Since the null filehandle uses the two argument form of L<perlfunc/open>
+it interprets special characters, so if you have a script like this:
+
+    while (<>) {
+        print;
+    }
+
+and call it with C<perl dangerous.pl 'rm -rfv *|'>, it actually opens a
+pipe, executes the C<rm> command and reads C<rm>'s output from that pipe.
+If you want all items in C<@ARGV> to be interpreted as file names, you
+can use the module C<ARGV::readonly> from CPAN.
+
 You can modify @ARGV before the first <> as long as the array ends up
 containing the list of filenames you really want.  Line numbers (C<$.>)
 continue as though the input were one big happy file.  See the example
diff --git a/pod/perlrun.pod b/pod/perlrun.pod
index c2b53932eb..1b8f1a0296 100644
--- a/pod/perlrun.pod
+++ b/pod/perlrun.pod
@@ -655,6 +655,10 @@ Note that the lines are not printed by default.  See B<-p> to have
 lines printed.  If a file named by an argument cannot be opened for
 some reason, Perl warns you about it and moves on to the next file.
 
+Also note that C<< <> >> passes command line arguments to
+L<perlfunc/open>, which doesn't necessarily interpret them as file names.
+See  L<perlop> for possible security implications.
+
 Here is an efficient way to delete all files that haven't been modified for
 at least a week: