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POParent process needs to wait for child to finnish setup
 

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  1. POParent process needs to wait for child to finnish setup
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    <p>Hello guys so my code is supposed to create an unlimited amount of processes each running their own program and communicating threw pipes..</p> <p>This is done in a recursive way so that the first parent creates a pipe then a child.. After this the child does the same creating a pipe2 and child2 etc....</p> <p>Problem is that the parent process doesn't want to wait for all the children to be created and when I try to insert</p> <pre><code>waitpid(childpid, NULL, 0); </code></pre> <p>it kinda waits forever... So either I want the last child to send some kind of STOP WAIT signal or I would like another way to solve this problem!</p> <p>Here is the code:</p> <pre><code>/* workForce.c * * Program created by ----Secret----- * * Input has to be the programs you wish the workForce to execute with following parameters seperated by '0's * * example input: * printenv 0 grep L 0 sort * * Will result in the command: printenv | grep L | sort | chosen PAGER * * The program will pipe each unit of the workForce to the next unit untill it reaches the last unit where * it will printout the result to STDOUT. */ #include &lt;sys/types.h&gt; #include &lt;sys/wait.h&gt; #include &lt;errno.h&gt; #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;unistd.h&gt; #include &lt;string.h&gt; #define PIPE_READ_SIDE ( 0 ) #define PIPE_WRITE_SIDE ( 1 ) pid_t childpid; /* för child-processens PID vid fork() */ /* * The generateWorkforce method automaticly creates it's own workforce with one process per taskset * Each unit in the work force will execute the parameters provided * As long as it's not the end of the workforce the unit will pipe its output to the next unit */ void generateWorkforce(int taskpointer, int totaltasks, int taskset[], char* tasks[]){ /* Create pipe then fork */ int pipe_filedesc[ 2 ]; int return_value; return_value = pipe( pipe_filedesc ); if( -1 == return_value ) {perror( "Cannot create pipe" ); exit( 1 );} childpid = fork(); if( 0 == childpid ) { /* Redirecting STDIN to now read from pipe instead and removing the pipe */ return_value = dup2( pipe_filedesc[ PIPE_READ_SIDE], STDIN_FILENO ); if( -1 == return_value){perror( "Cannot dup" ); exit( 1 );} return_value = close( pipe_filedesc[PIPE_READ_SIDE] ); if( -1 == return_value ){perror( "Cannot close read end" ); exit( 1 );} return_value = close( pipe_filedesc[ PIPE_WRITE_SIDE ] ); if( -1 == return_value ){perror( "Cannot close write end" ); exit( 1 );} if(taskpointer &lt; totaltasks-1){ generateWorkforce((taskpointer+taskset[taskpointer]), totaltasks, taskset, tasks); } else { kill(getppid, SIGINT); execlp(tasks[taskpointer], tasks[taskpointer], (char *) 0); /* exec only returns if an error occured */ perror( "Cannot exec execute[pointer]" ); exit( 1 ); } } else { if( -1 == childpid ){ perror( "Cannot fork()" ); exit( 1 );} /* Redirecting STDOUT to write to pipe instead and thereafter removes the pipe */ return_value = dup2( pipe_filedesc[ PIPE_WRITE_SIDE], STDOUT_FILENO ); if( -1 == return_value){perror( "Cannot dup" ); exit( 1 );} return_value = close( pipe_filedesc[ PIPE_WRITE_SIDE ] ); if( -1 == return_value ){perror( "Cannot close write end" ); exit( 1 );} return_value = close( pipe_filedesc[ PIPE_READ_SIDE ] ); if( -1 == return_value ){perror( "Cannot close read end" ); exit( 1 );} waitpid(childpid, NULL, 0); /* Will define what task to execute and how many parameters it needs */ if(taskset[taskpointer] &gt; 1){ char* execute[taskset[taskpointer]+1]; int i; char* executeHead = tasks[taskpointer]; execute[0] = tasks[taskpointer]; for(i = 1;i&lt;taskset[taskpointer];i++){ execute[i] = tasks[taskpointer+i]; } execute[taskset[taskpointer]] = (char *) 0; (void) execvp( executeHead, execute ); } else{ (void) execlp( tasks[taskpointer], tasks[taskpointer], (char *) 0 ); } /* exec only returns if an error occured */ perror( "Cannot exec tasks[taskpointer]" ); exit( 1 ); } } int main( int argc, char * argv[] ) { /* The following block will determine how many tasksets was in the input */ char * separator = "0"; int i; int j; int tasknr = 1; for(i = 1, j = 1;i&lt;(argc);i++) { if(!(strcmp(argv[(i)], separator ))){ j++; } else{ tasknr++; } } char* execute[tasknr]; int taskset[j+1]; /* Will fill the taskset array and execute array */ if(getenv("PAGER")) execute[(tasknr-1)] = getenv("PAGER"); else execute[(tasknr-1)] = "less"; taskset[j] = 1; taskset[0] = 0; int k = 0; for(i = 1, j = 0;i&lt;(argc);i++) { if(!(strcmp(argv[(i)], separator ))){ j++; taskset[j] = 0; } else{ execute[k] = argv[i]; taskset[j]++; k++; } } generateWorkforce(0, tasknr, taskset, execute); exit( 0 ); } </code></pre> <p>EDIT: the kill(getppid, SIGINT); was an attempt to stop the wait!</p>
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    1. USDavid Ekermann
    1. USDavid Ekermann
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    1. CO-1 != waitpid( pid, &status, WNOHANG ) <<< can you use that in the mainloop?
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      1. POParent process needs to wait for child to finnish setup
      1. USJekyll
    2. COChanged the waitpid I had for that, but it ended up being the same as not waiting at all.
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      1. USDavid Ekermann
    3. COSo the main(starter) process creates a child and the child creates another one - like a process list, correct? And you want the main proc to not wait at all, right?
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      1. POParent process needs to wait for child to finnish setup
      1. USChris
 

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