Implement Pipe in C -

i implementing pipe in c. when try command 'cat aa | grep "something" ' in program. grep process hanging there, seems waiting input. don't know why. here core code. take executecommand call execve function , arguments correctly passed.

if ((pid = fork()) < 0) {     perror("fork failed\n");     exit(1); }                if (pid) {   // parent pipe writer     close(pd[0]);     close(1);     // replace input pipe     dup(pd[1]);      // recursively call next commands     executecommand(cmds, env);     freecommandsarray(&cmds);      exit(0); } else {   // child pipe reader     close(pd[1]);     close(0); // close read end     dup(pd[0]);     executecommand(*(++splitcmds), env);     freecommandsarray(&cmds);     exit(0); } 

the full code open. problem have use full path of command file first parameter execve (e.g. /bin/ls ls), otherwise, got error message, no such file existed.

it quotation mark @ first argument of grep cause problem. works if rid of on input. e.g 'cat aa | grep drw' instead of 'cat aa | grep "something"'