Forking Multiple Children

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

i have written this program and would like to adapt it so that it would accept 1 to 3 commands and not just 3. and execute the commands if anyone could help it would be most appreciated.



#!/usr/local/bin/perl -w



pipe PIPEIN1,PIPEOUT1;#pipe1

pipe PIPEIN2,PIPEOUT2;#pipe2

$command1=<STDIN>; # read command 1 from user

        chomp($command1); # remove new line character

 $command2=<STDIN>; # read command 2 from user

        chomp($command2); # remove new line character

 $command3=<STDIN>; # read command 3 from user

        chomp($command3); # remove new line character
if (fork ==0)#child 1

        {
        close PIPEIN1; # close pipe in 1

        close PIPEIN2; # close pipe in 2

        close PIPEOUT2; # close pipe out 2

        close STDOUT; # close standard out

        open STDOUT, ">&PIPEOUT1"; #open standard out and pipe1
        
        exec $command1;
        }
 if (fork==0)#child 2
     {
     close PIPEIN2; #close pipe in 2
     close PIPEOUT1; # close pipe out 1
     close STDIN; # close standard in
     open STDIN, "<&PIPEIN1";# open standard in and pipe1
     close STDOUT; # close standard out
     open STDOUT, ">&PIPEOUT2";# open standard out and pipe 2
     
        exec $command2;
     
     }
 if (fork==0)#child 3
        {
        close PIPEIN1; # close pipe in 1
        close PIPEOUT1; # close pipe out 1
        close PIPEOUT2; # close pipe out 2
        close STDIN; # close standard in
        open STDIN, "<&PIPEIN2"; # open standard in and pipe in 2
        
        exec $command3;
        }
   close PIPEIN1; # close pipe in 1
   close PIPEOUT1; # close pipe out 1
   close PIPEIN2; # close pipe in 2
   close PIPEOUT2; # close pipe out 2
   wait; # wait for child 1 to terminate
   wait; # wait for child 2 to terminate
   wait; # wait for child 3 to terminate
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Edit - ar0n More descriptive title

Comment on Forking Multiple Children Download Code

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(Knob)Re: Forking Multiple Children by knobunc (Pilgrim) on Jun 19, 2001 at 16:36 UTC
You appear to be passing the commands in to the standard input of the program. If there isn't a good reason for that then you can pass them on the command line: `my ($command1, $command2, $command3) = @ARGV; $command2 = 'default' unless defined $command2; $command3 = 'hoo hah' unless defined $command3; # OR my $command1 = shift or die; # Ideally call a subroutine to print usag +e and die my $command2 = shift \|\| 'default'; my $command3 = shift \|\| 'hoo hah';` [download] If you have to read from `STDIN` then you can check to see if it still has stuff available using the `eof` function: `my $command1 = <STDIN>; chomp($command1); my ($command2, $command3) = ('default', 'hoo hah'); unless (eof(STDIN)) { $command2 = <STDIN>; chomp $command2; unless (eof(STDIN)) { $command3 = <STDIN>; chomp $command3; } }` [download] -ben	[reply] [d/l] [select]

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(Knob)Re: Forking Multiple Children
by knobunc (Pilgrim) on Jun 19, 2001 at 16:36 UTC

You appear to be passing the commands in to the standard input of the program. If there isn't a good reason for that then you can pass them on the command line:

my ($command1, $command2, $command3) = @ARGV;
$command2 = 'default' unless defined $command2;
$command3 = 'hoo hah' unless defined $command3;

# OR

my $command1 = shift or die; # Ideally call a subroutine to print usag
+e and die
my $command2 = shift || 'default';
my $command3 = shift || 'hoo hah';
[download]

If you have to read from STDIN then you can check to see if it still has stuff available using the eof function:

my $command1 = <STDIN>; chomp($command1);
my ($command2, $command3) = ('default', 'hoo hah');
unless (eof(STDIN)) {
    $command2 = <STDIN>; chomp $command2;

    unless (eof(STDIN)) {
        $command3 = <STDIN>; chomp $command3;
    }
}
[download]

-ben

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