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PORun N concurrent processes in C
 

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  1. PORun N concurrent processes in C
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    <p>I am trying to run N concurrent processes in a C program. I've built a simple example that takes commands as arguments, creates a fork for each one, and executes it.</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;unistd.h&gt; int main(int argc, char **argv) { int i; for(i = 1; i &lt; argc; i++) { pid_t pid = fork(); if(pid &lt; 0) { fprintf(stderr, "forking error\n"); exit(1); } else if(pid &gt; 0) { int status; waitpid(pid, &amp;status, 0); printf("Command %s has completed successfully by PID=%d\n", argv[i], pid); } else { char cmd[1024]; sprintf(cmd, "%s", argv[i], i); system(cmd); _exit(1); } } printf("Finished\n"); return 0; } </code></pre> <p>This seems to run the processes correctly, but not concurrently. Any ideas as to what am I doing wrong?</p> <p><strong>EDIT</strong>: I've edited based on suggestions, but this also does not seem to work.</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;unistd.h&gt; int main(int argc, char **argv) { int i; pid_t *pids = malloc( sizeof(pid_t) * (argc) ); int *statuses = malloc( sizeof(int) * (argc) ); for(i = 1; i &lt; argc; i++) { pid_t pid = fork(); if(pid &lt; 0) { fprintf(stderr, "forking error\n"); exit(1); } else if(pid &gt; 0) { //int status; //waitpid(pid, &amp;status, 0); //printf("Command %s has completed successfully by PID=%d\n", argv[i], pid); pids[i] = pid; } else { char cmd[1024]; sprintf(cmd, "%s &gt; out.%d", argv[i], i); system(cmd); _exit(1); } } int needtowait = 0; do { needtowait = 0; for(i = 1; i &lt; argc; i++) { if(pids[i] &gt; 0) { if(waitpid(pids[i], &amp;statuses[i], 0) != 0) { pids[i] = 0; char *successstr = "successfully"; if(statuses[i]) { successstr = "unsuccessfully"; } printf("Command %s has completed %s by PID=%d\n", argv[i], successstr, pids[i]); } } else { needtowait = 1; } sleep(0); } } while(needtowait); printf("Finished!\n"); return 0; } </code></pre>
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