c - Why does using `execl` instead of `system` stops my program from working? -


i'm trying basic ipc using pipes. spent hours searching internet, doing , that, reading api documentations, , ended code below. not work, quite expected. making code 'work' many thanks.

<edit>
i've found using system instead of execl makes program run expected. going wrong here when use execl, while doesn't happen system function?
</edit>

#include <stdio.h> #include <stdlib.h> #include <unistd.h>  int main(void){     int hinpipe[2];     int houtpipe[2];     file *hinfile;     file *houtfile;     char *s;      pipe(hinpipe);     pipe(houtpipe);     if(fork()){         close(hinpipe[0]);         close(houtpipe[1]);         hinfile=fdopen(hinpipe[1],"w");         fprintf(hinfile,"2^100\n");         fclose(hinfile);         houtfile=fdopen(houtpipe[0],"r");         fscanf(houtfile,"%ms",&s);         fclose(houtfile);         printf("%s\n",s);         free(s);     }else{         dup2(hinpipe[0],stdin_fileno);         dup2(houtpipe[1],stdout_fileno);         close(hinpipe[0]);         close(hinpipe[1]);         close(houtpipe[0]);         close(houtpipe[1]);          system("bc -q");/*this works*/         /*execl("bc","-q",null);*/ /*but doesn't*/     } }

read fine man page. :)

execl(const char *path, const char *arg0, ... /*, (char *)0 */);

arg0 (aka argv[0], name program told invoked under) not same argument path (the location of executable said program). moreover, execl takes, first argument, fully-qualified pathname.

thus, want:

execl("/usr/bin/bc", "bc", "-q", null);

...or, search path bc rather hardcoding location:

execlp("bc", "bc", "-q", null);

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