This section describes how you can perform various other operations on file descriptors, such as inquiring about or setting flags describing the status of the file descriptor, manipulating record locks, and the like. All of these operations are performed by the function fcntl . The second argument to the fcntl function is a command that specifies which operation to perform. The fcntl function performs the operation specified by command on the file descriptor filedes .
Some commands require additional arguments to be supplied.
These additional arguments and the return value and error conditions are given in the detailed descriptions of the individual commands. Briefly, here is a list of what the various commands are. See Duplicating Descriptors . Get flags associated with the file descriptor. See Descriptor Flags .