File descriptor

System resource identifier in operating systems / From Wikipedia, the free encyclopedia

Dear Wikiwand AI, let's keep it short by simply answering these key questions:

Can you list the top facts and stats about File descriptor?

Summarize this article for a 10 year old


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:

Table info: Integer value, Name, .mw-parser-output .monos...
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

Oops something went wrong: