File descriptor

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

File descriptor

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

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