Think about the overhead involved. Here is my brief analysis:

open(INFILE,"cat textfile |")
while(<INFILE>) {...}
[download]

This opens a type of file handle commonly known as a pipe. It spawns an additional process, complete with a duplicate set of environment variables and memory management requirements. The OS must now swap memory back and forth between Perl and cat.

open(INFILE,"textfile")
while(<INFILE>) {...}
[download]

Perl opens a file handle directly to the file. No other processes are started.

system("cat textfile | filter.pl")
[download]

Perl invokes the shell which invokes cat and another instance of Perl! Plus the shell still has to open a file handle for the output of cat / the input to filter.pl

Result: All three methods require a filehandle (aka a fileno, or a file descriptor) and two of the methods have the additional overhead of multiple processes. Use the second method and avoid all that.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.