Re: Re: What is a pipe and why would I want to use one?

[fsn]

This is a very very simple (and probably Linuxcentric) attempt to illustrate how you can send data from one program to another using a pipe:

./Daddy.pl:

#!/usr/bin/perl

$i=0;
open SESAME,"|./Kiddy.pl";      # Open up the pipe

while ( $i++<10) {
        print SESAME "Testing IPC with pipes. Line $i.\n";      # Prin
+t to pipe
}

close SESAME;    # This (or the termination of the program)
                 # closes the pipe. The other side recieves this
                 # as an EOF (End OF File).

./Kiddy.pl:

#!/usr/bin/perl

while ($in=<STDIN>) {                # Read from <STDIN> until <EOF>
        chomp $in;                   # Remove <NL>
        print "By Kiddy.pl: $in\n";   # Print out what we read
}

There are some extra fluff in Kiddy.pl, the use of chomp and $in instead of $_ f.ex., but I kept it there to make it more clear, at least to me.

If you run the above you would get this:

$ ./Daddy.pl
By Kiddy.pl: Testing IPC with pipes. Line 1.
By Kiddy.pl: Testing IPC with pipes. Line 2.
By Kiddy.pl: Testing IPC with pipes. Line 3.
By Kiddy.pl: Testing IPC with pipes. Line 4.
By Kiddy.pl: Testing IPC with pipes. Line 5.
By Kiddy.pl: Testing IPC with pipes. Line 6.
By Kiddy.pl: Testing IPC with pipes. Line 7.
By Kiddy.pl: Testing IPC with pipes. Line 8.
By Kiddy.pl: Testing IPC with pipes. Line 9.
By Kiddy.pl: Testing IPC with pipes. Line 10.
$

Note that Daddy.pl is not printing to the screen at all, Kiddy.pl is doing all that.