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Re^3: Reading two text files parallelly...by Marshall (Canon) |
on Nov 09, 2010 at 16:13 UTC ( [id://870330]=note: print w/replies, xml ) | Need Help?? |
With open (FH, "<$file1") or die "blahblah"; there is a possible security issue because maybe the variable $file1 might contain something that would cause problems. What goes in to the open() function is the interpolated string. You learned right, always use the < or > etc. In your example, if $file1 was ">ImportantFile", the open() will fail because the argument would evaluate to "<>ImportantFile" and open() won't like that filename! If you forgot the "<", then then open to ">ImportantFile" might succeed and it would be deleted or other various bad things could happen. So if you use: open (FH, '<', $file1) || die; putting the file mode explicitly there is a "small" thing that could save you big problems later. If you are writing small one or two page programs, using a bare word like FH is no big deal. However, be aware that Perl like C (you have do it this way in C), can use lexical variables for filehandles. So you can open($infile, '<', $somefile)... and pass $infile to a subroutine just like any other Perl variable. As far as $! in "die" messages, you might or might not want to put that there. Part of this depends upon how descriptive your part of the "die" message is! Ok, try some code: See what $! has to say. My OS prints, "your textXXX OS says: No such file or directory". I figure that "your textXXX" is way more important. Something like "can't open Budget.csv" is way more to the point than "No such file or directory"- most of the time the OS text is meaningless for the average user. Also notice what adding the trailing "\n" to the die message does. Update: This thread has morphed into something else from the OP's original question. But I figure it is ok to comment on some of the comments to the comments!
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