How to see the processId of the process called by system command from perl

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

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Re: How to see the processId of the process called by system command from perl by apl (Monsignor) on Apr 16, 2008 at 20:17 UTC
Take a look at How do i obtain the PID of a program already running.. Categorized Q&A is your friend!	[reply]
Re: How to see the processId of the process called by system command from perl by pc88mxer (Vicar) on Apr 16, 2008 at 20:13 UTC
You'll need to `fork` the R script yourself like this: `my $pid; defined($pid = fork()) or die "unable to fork: $!\n"; if ($pid == 0) { # child exec(...); # exec R script here die "unable to exec: $!\n"; } # parent continues here` [download] Note that depending on how you call `exec`, `$pid` will either be the pid of the R command or the pid of a shell that perl creates to invoke the R command. Examples: `exec("R", "and", "some", "args"); # $pid will be the R command exec("R and some args > out"); # $pid will be that of a shell` [download]	[reply] [d/l] [select]
Re: How to see the processId of the process called by system command from perl by elmex (Friar) on Apr 16, 2008 at 20:14 UTC
How are you calling the R script? With the `system` function? Are you forking before you call it? Is the script going to the background? Best way would probably be to fork and call the R script in that new process via `system`: `my $pid = fork; defined $pid or die "fork failed: $!"; if ($pid) { # in parent: waitpid $pid; # wait for the child, which's pid is in $pid } else { # in child: system ("R ..."); exit; }` [download]	[reply] [d/l]
Re: How to see the processId of the process called by system command from perl by BrowserUk (Patriarch) on Apr 16, 2008 at 22:06 UTC
You can use a piped open to get the pid: `my $pid = open my $cmd, "-\|", 'theCommand parms' or die $!;` [download] On win32, you can use the return value from system`1, ...`: `my $pid = system 1, 'theCommand parms';` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l] [select]
Re: How to see the processId of the process called by system command from perl by walto (Pilgrim) on Apr 17, 2008 at 04:03 UTC
On Linux you can use: my $pid = `pidof R`;	[reply] [d/l]
Re^2: How to see the processId of the process called by system command from perl by Anonymous Monk on Jan 31, 2012 at 14:19 UTC
with pidof how to get the output of othe command which gets executed. For example if the command to be executed is "date" I want to get the output of the command to a perl variable and also the pid number.	[reply]
Re^3: How to see the processId of the process called by system command from perl by Corion (Patriarch) on Jan 31, 2012 at 14:22 UTC
Have you read the pidof manpage? It tells you what `pidof` does. It only finds the pid of a running process. It does not launch a process.	[reply] [d/l]