You need to close the pipe fds in the parent, or the child won't receive EOF, because the pipe's still open for writing in the parent. This would cause the second wait()
to hang. Works for me:
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char** argv)
{
int des_p[2];
if(pipe(des_p) == -1) {
perror("Pipe failed");
exit(1);
}
if(fork() == 0) //first fork
{
close(STDOUT_FILENO); //closing stdout
dup(des_p[1]); //replacing stdout with pipe write
close(des_p[0]); //closing pipe read
close(des_p[1]);
const char* prog1[] = { "ls", "-l", 0};
execvp(prog1[0], prog1);
perror("execvp of ls failed");
exit(1);
}
if(fork() == 0) //creating 2nd child
{
close(STDIN_FILENO); //closing stdin
dup(des_p[0]); //replacing stdin with pipe read
close(des_p[1]); //closing pipe write
close(des_p[0]);
const char* prog2[] = { "wc", "-l", 0};
execvp(prog2[0], prog2);
perror("execvp of wc failed");
exit(1);
}
close(des_p[0]);
close(des_p[1]);
wait(0);
wait(0);
return 0;
}
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