practical examples use dup or dup2

by

One example use would be I/O redirection. For this you fork a child process and close the stdin or stdout file descriptors (0 and 1) and then you do a dup() on another filedescriptor of your choice which will now be mapped to the lowest available file descriptor, which is in this case 0 or 1.

Using this you can now exec any child process which is possibly unaware of your application and whenever the child writes on the stdout (or reads from stdin, whatever you configured) the data gets written on the provided filedescriptor instead.

Shells use this to implement commands with pipes, e.g. /bin/ls | more by connecting the stdout of one process to the stdin of the other.

More Related Contents:

  1. How do I get a thread ID from an arbitrary pthread_t?
  2. How can I convert a file pointer ( FILE* fp ) to a file descriptor (int fd)?
  3. C reading from file
  4. how to enter a function to a file in c
  5. How to debug why my C code causes a segmentation fault? [closed]
  6. C: Reading strings from binary file
  7. How to read the content of a file to a string in C?
  8. what’s the differences between r and rb in fopen
  9. In C how do you redirect stdin/stdout/stderr to files when making an execvp() or similar call?
  10. Why is “while( !feof(file) )” always wrong?
  11. Color text in terminal applications in UNIX [duplicate]
  12. How to use EOF to run through a text file in C?
  13. How do you get a directory listing in C?
  14. read line by line in the most efficient way *platform specific*
  15. Getting absolute path of a file
  16. Why does open() create my file with the wrong permissions?
  17. Set environment variables in C
  18. C, reading from file into structure
  19. Understanding concurrent file writes from multiple processes
  20. fd leak, custom Shell
  21. Writing to stdin and reading from stdout (UNIX/LINUX/C Programming)
  22. *nix select and exceptfds/errorfds semantics
  23. How do I reimplement (or wrap) a syscall function on Linux?
  24. How to check if a file is already open by another process in C?
  25. What can cause a “Resource temporarily unavailable” on sock send() command
  26. How to read all files in a folder using C
  27. Executing a shared library on Unix
  28. Unix O_CREAT flag without mode specified
  29. How to declare a structure in a header that is to be used by multiple files in c?
  30. Where can I find system call source code?

Leave a Comment