cat | cat | ls

[jnspr]

Should behave like this:

• Press enter two times and you get back to your shell

Why it happens?

• ls writes to STDOUT and exits, the read end of the pipe is closed
• The user presses enter
• The first cat writes \n to its write end of the pipe
• The second cat reads it from the pipe
• The second cat writes to its write end, but the read end has been closed because ls has exited already
• The second cat exits aswell because write() returned zero or -1 (or it catches a SIGPIPE)
• The user presses enter again
• The first cat tries to write \n to the pipe but fails because the second cat exited aswell
• The first cat exits and the user is thrown back to the prompt

[jnspr]

For n number of cats, enter has to be pressed n times

[Dsite42]

fixed it by change the else to else if: else if (piping_data->prev_read != STDIN_FILENO)
in file input_redirections.c