Back Descriptor de fitxer Catalan Deskriptor souboru Czech Handle#Datei-Handle German Descriptor de archivo Spanish توصیفگر پرونده Persian Descripteur de fichier French Descritor de ficheiro Galician Descrittore di file Italian ファイル記述子 Japanese 파일 서술자 Korean
In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a process-unique identifier (handle) for a file or other input/output resource, such as a pipe or network socket.
File descriptors typically have non-negative integer values, with negative values being reserved to indicate "no value" or error conditions.
File descriptors are a part of the POSIX API. Each Unix process (except perhaps daemons) should have three standard POSIX file descriptors, corresponding to the three standard streams:
| Integer value | Name | <unistd.h> symbolic constant[1] | <stdio.h> file stream[2] |
|---|---|---|---|
| 0 | Standard input | STDIN_FILENO | stdin |
| 1 | Standard output | STDOUT_FILENO | stdout |
| 2 | Standard error | STDERR_FILENO | stderr |
- ^ The Open Group. "The Open Group Base Specifications Issue 7, IEEE Std 1003.1-2008, 2016 Edition". Retrieved 2017-09-21.
- ^ The Open Group. "The Open Group Base Specifications Issue 7, IEEE Std 1003.1-2008, 2016 Edition". <stdio.h>. Retrieved 2017-09-21.