How to pipe different processes? (C) - c

Question

I'm trying to pipe two different processes to implement the terminal's functionality "|".
I need the new child to execute a command itself, and fork another process to execute a different command using the first process's output, then output the final process's results on the terminal.
Here's my code, I keep the original parent untouched because I need to continue executing the other parts of my program afterwards.
int exec_pipe(char **args, int index, int *i, char**** jobs){
int fd1[2];
pid_t pid, wpid;
int status;
int savedStdOut = dup(1);
int savedStdIn = dup(fileno(stdin));
if (pipe(fd1)==-1)
{
fprintf(stderr, "Pipe Failed" );
return 1;
}
pid = fork();
if (pid < 0)
{
fprintf(stderr, "fork Failed" );
return 1;
}else if (pid == 0)
{
// Child process
close(fd1[0]);
dup2(fd1[1], 1);
printf("%s\n", args[index - 1]);
if (execvp(args[0], args) == -1)
{
printf("command not found\n");
}
int childId = fork();
if(childId < 0){
fprintf(stderr, "fork Failed" );
return 1;
}else if(childId == 0){
// child of child of parent
fdopen(fd1[1], "r");
dup2(fd1[1], savedStdOut);
if (execvp(args[index + 1], args) == -1)
{
printf("command not found\n");
}
exit(EXIT_FAILURE);
}else {
// parent of child of child of parent
do
{
wpid = waitpid(pid, &status, WUNTRACED);
} while (!WIFEXITED(status) && !WIFSIGNALED(status)); // wait for child until it's exited or been killed
fdopen(savedStdIn, "r");
close(fd1[0]);
close(fd1[1]);
}
}else{
// Parent process
do
{
wpid = waitpid(pid, &status, WUNTRACED);
} while (!WIFEXITED(status) && !WIFSIGNALED(status)); // wait for child until it's exited or been killed
}
return 1;
}
I'm getting a "No such file or directory" error with the program ending with exit code 9.

Answer 1

Solved it based on some comments, thanks all!
int fd1[2];
pid_t pid;
// allocate two pipe sets
if (pipe(fd1) < 0)
{
perror("Failed to create pipe.");
return EXIT_FAILURE;
}
// launch first child process.
if ((pid = fork()) < 0)
{
perror("Failed to fork child(1)");
return EXIT_FAILURE;
}
if (pid == 0)
{
// child
// stdout = fd1(write)
if(strcmp(args[0], args[index - 1]) == 0)
{
dup2(fd1[WRITE], STDOUT_FILENO);
close(fd1[READ]);
close(fd1[WRITE]);
execlp(args[0], args[0], (char*) NULL);
fprintf(stderr, "failed to execute '%s'\n", args[0]);
exit(1);
}else{
dup2(fd1[WRITE], STDOUT_FILENO);
close(fd1[READ]);
close(fd1[WRITE]);
execlp(args[0], args[0], args[index - 1], (char*) NULL);
fprintf(stderr, "failed to execute '%s'\n", args[0]);
exit(1);
}
}else
{
// parent
// fork once more.
if ((pid = fork()) < 0)
{
perror("Failed to fork child(2)");
return EXIT_FAILURE;
}
if (pid == 0)
{
// child of child
// stdin = fd1(read)
dup2(fd1[READ], STDIN_FILENO);
close(fd1[WRITE]);
close(fd1[READ]);
execlp(args[index + 1], args[index + 1], (char*) NULL);
fprintf(stderr, "failed to execute '%s'\n", args[index + 1]);
exit(1);
}else{
int status;
close(fd1[READ]);
close(fd1[WRITE]);
waitpid(pid, &status, 0);
}
}