how to control popen stdin, stdout, stderr redirection?

by

popen(3) is just a library function, which relies on fork(2) and pipe(2) to do the real work.

However pipe(2) can only create unidirectional pipes. To send the child process input, and also capture the output, you need to open two pipes.

If you want to capture the stderr too, that’s possible, but then you’ll need three pipes, and a select loop to arbitrate reads between the stdout and stderr streams.

There’s an example here for the two-pipe version.

More Related Contents:

  1. printf anomaly after “fork()”
  2. How to make child process die after parent exits?
  3. Differences between fork and exec
  4. How to get the current directory in a C program?
  5. How to capture Control+D signal?
  6. Why does this program print “forked!” 4 times?
  7. Re-opening stdout and stdin file descriptors after closing them
  8. Using SO_REUSEADDR – What happens to previously open socket?
  9. Turn a simple socket into an SSL socket
  10. What are .a and .so files?
  11. Are there any platforms where using structure copy on an fd_set (for select() or pselect()) causes problems?
  12. After forking, are global variables shared?
  13. how to convert datetime to unix timestamp in c?
  14. Are file descriptors shared when fork()ing?
  15. Detecting 64bit compile in C
  16. What are the differences between poll and select?
  17. practical examples use dup or dup2
  18. Is it necessary to reset the fd_set between select system call?
  19. Socketpair() in C/Unix
  20. fork and existing threads?
  21. Why the address of variable of child process and parent process is same
  22. *nix select and exceptfds/errorfds semantics
  23. Questions about putenv() and setenv()
  24. In C, what’s the size of stdout buffer?
  25. What do pty and tty mean?
  26. fork() and wait() with two child processes
  27. Executing a shared library on Unix
  28. How can I flush unread data from a tty input queue on a UNIX system?
  29. ungetc: number of bytes of pushback
  30. What’s the difference between “C system calls” and “C library routines”?

Leave a Comment