Is close/fclose on stdin guaranteed to be correct?

by

fclose(stdin) causes any further use of stdin (implicit or explicit) to invoke undefined behavior, which is a very bad thing. It does not “inhibit input”.

close(fileno(stdin)) causes any further attempts at input from stdin, after the current buffer has been depleted, to fail with EBADF, but only until you open another file, in which case that file will become fd #0 and bad things will happen.

A more robust approach might be:

int fd = open("/dev/null", O_WRONLY);
dup2(fd, 0);
close(fd);

with a few added error checks. This will ensure that all reads (after the current buffer is depleted) result in errors. If you just want them to result in EOF, not an error, use O_RDONLY instead of O_WRONLY.

More Related Contents:

  1. ‘ ‘, ‘\n’ , scanf() and output screen
  2. How to work with a variable number of variables in C?
  3. How to read / parse input in C? The FAQ
  4. Rerouting stdin and stdout from C
  5. What are the rules of automatic stdout buffer flushing in C?
  6. Code for printf function in C [duplicate]
  7. Reading a line using scanf() not good?
  8. stdlib and colored output in C
  9. What’s the best way to return a random line in a text file using C?
  10. What will happen if ‘&’ is not put in a ‘scanf’ statement?
  11. Is there a Windows equivalent to fdopen for HANDLEs?
  12. GCC fatal error: stdio.h: No such file or directory
  13. How can you flush a write using a file descriptor?
  14. What is the difference between getch() and getchar()?
  15. C equivalent to fstream’s peek
  16. printf not printing to screen
  17. Why does forking my process cause the file to be read infinitely
  18. What exactly is the FILE keyword in C?
  19. Unable to open a file with fopen()
  20. whitespace in the format string (scanf)
  21. Why does this code print two times? [duplicate]
  22. How can one flush input stream in C?
  23. ftell at a position past 2GB
  24. Tried and true simple file copying code in C?
  25. ungetc: number of bytes of pushback
  26. How do you type something on the same line of text in C [closed]
  27. How to create type safe enums?
  28. sem_init on OS X
  29. Why is printf round floating point numbers up?
  30. Why can I change the value of a const char* variable?

Leave a Comment