Implementing shell in C and need help handling input/output redirection

Question

Round 2

After reading some of the answers, my revised code is:

int pid = fork();

if (pid == -1) {
    perror(\"fork\");
} else if (pid == 0) {   
         


        

Answer 1

Here's what's happening. After you call fork() there are two processes executing that are duplicates of the original process. The difference is in the return value of fork() which is stored in pid.

Then both processes (the shell and the child) redirect their stdin and stdout to the same files. I think you were trying to save the previous fd in current_out, but as Seth Robertson points out, this doesn't currently work, since the wrong file descriptor is being saved. The parent also restores its stdout, but not stdin.

You could fix this bug, but you can do better. You don't actually have to redirect parent's output, just the child's. So simply check pid first. Then there is also no need to restore any file descriptors.