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Full Discussion: understanding thread in perl
Top Forums Shell Programming and Scripting understanding thread in perl Post 302694209 by PranavEcstasy on Thursday 30th of August 2012 09:27:11 AM
Old 08-30-2012
understanding thread in perl

Hi all,

I am trying to build threads which will go to localhost and list the files in given folder.

Code:
#!/usr/bin/perl
use threads;
        my $t1 = threads->new(\&sub1, 1);
        my $t2 = threads->new(\&sub2, 2);
     push(@threads,$t1);
      push(@threads,$t2);
 
foreach (@threads) {
my $num = $_->join
} 
 
sub sub1 {
        print "-----started thread 1-----\n";
        system("ssh localhost ls -l /home/user1");
        print "*****done with thread 1*****\n";
        return 1;
sub sub2 {
        print "-----started thread 2-----\n";
        system("ssh localhost ls -l /home/user2");
        print "*****done with thread 2*****\n";
        return 2;
}



I will be very greatfull if someone can explain me the working of BOLD portion and why are they necessory.
If we remove them, perl will simply exit saying 2 threads started 0 unjoined . and will not list the files.

I am using bash Linux bash shell.

Last edited by PranavEcstasy; 08-30-2012 at 10:34 AM..
 

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thr_join(3C)						   Standard C Library Functions 					      thr_join(3C)

NAME
thr_join - wait for thread termination SYNOPSIS
cc -mt [ flag... ] file...[ library... ] #include <thread.h> int thr_join(thread_t thread, thread_t *departed, void **status); DESCRIPTION
The thr_join() function suspends processing of the calling thread until the target thread completes. The thread argument must be a member of the current process and cannot be a detached thread. See thr_create(3C). If two or more threads wait for the same thread to complete, all will suspend processing until the thread has terminated, and then one thread will return successfully and the others will return with an error of ESRCH. The thr_join() function will not block processing of the calling thread if the target thread has already terminated. If a thr_join() call returns successfully with a non-null status argument, the value passed to thr_exit(3C) by the terminating thread will be placed in the location referenced by status. If the target thread ID is 0, thr_join() finds and returns the status of a terminated undetached thread in the process. If no such thread exists, it suspends processing of the calling thread until a thread for which no other thread is waiting enters that state, at which time it returns successfully, or until all other threads in the process are either daemon threads or threads waiting in thr_join(), in which case it returns EDEADLK. See NOTES. If departed is not NULL, it points to a location that is set to the ID of the terminated thread if thr_join() returns successfully. RETURN VALUES
If successful, thr_join() returns 0. Otherwise, an error number is returned to indicate the error. ERRORS
EDEADLK A joining deadlock would occur, such as when a thread attempts to wait for itself, or the calling thread is waiting for any thread to exit and only daemon threads or waiting threads exist in the process. ESRCH No undetached thread could be found corresponding to the given thread ID. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
thr_create(3C), thr_exit(3C), wait(3C), attributes(5), standards(5) NOTES
Using thr_join(3C) in the following syntax, while (thr_join(0, NULL, NULL) == 0); will wait for the termination of all non-daemon threads, excluding threads that are themselves waiting in thr_join(). SunOS 5.10 27 Mar 2000 thr_join(3C)
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