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Using system function to run xview

Posted on 2004-04-24
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Last Modified: 2006-11-17
I am writing C++ code (Linux) to display an image file using xview.  After the image is displayed for 10 seconds, how do I go about displaying the next file considering that I cannot launch xview again unless I close out the original display?

I tried this:

system("xview imageFile.pbm");
sleep(10);
system("xview imageFile2.pbm");

The only way I can shut down the application if I do a CTRL-C.  How can I capture those keystrokes and use it within the system function?  The only other way, which I was hoping I wouldn't have to do is use the system function to write out the process ids to a file then read that file and get the process id that corresponds to the xview.
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Question by:jewee
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LVL 86

Expert Comment

by:jkr
ID: 10908893
You'd use 'fork()' and 'exec()' for that, e.g.

while ( true) {

    char* image = "imageFile.pbm";
    pid_t pid;

    pid = fork ();

    if ( 0 == pid) { // child process, spawn xview

        execl ( "xview", "xview", image);

    } else { // main process, wait 10s, then kill xview and restart it again

        sleep ( 10);
        kill ( pid, SIGKILL);
    }
}
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Author Comment

by:jewee
ID: 10909059
What header file do I need to include?
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LVL 86

Expert Comment

by:jkr
ID: 10909088
You'll need

    #include <stdio.h>
    #include <stdlib.h>
    #include <errno.h>
    #include <unistd.h>
    #include <sys/types.h>
    #include <sys/wait.h>
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LVL 86

Expert Comment

by:jkr
ID: 10909092
BTW, see also http://www.ecst.csuchico.edu/~beej/guide/ipc/fork.html ("A fork() Primer")
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Author Comment

by:jewee
ID: 10909752
Thank you for your help!  I tried your code and noticed that the execl command doesn't work.  XView does not execute.
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Author Comment

by:jewee
ID: 10910006
I tried entering the path of xview but it said "image not found".  For the image, I included the path but it still didn't work.

I noticed that if I use the same code you provided me, but instead of using execl, I used system, then incremented the pid after, it worked but would only launch xview once.
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LVL 86

Accepted Solution

by:
jkr earned 500 total points
ID: 10910150
>>and noticed that the execl command doesn't work.

My fault - if should be

       execl ( "xview", "xview", image, NULL);

:-(


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