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File control.

#include <fcntl.h>

fcntl(int fd, int cmd, ...);


The fcntl() system call provides for control over descriptors. The argument fd is a descriptor to be operated on by cmd as described below. Depending on the value of cmd, fcntl() can take an additional third argument int arg.

F_GETFL Get descriptor status flags, as described below (arg is ignored).
F_SETFL Set descriptor status flags to arg.

The flags for the F_GETFL and F_SETFL flags are as follows:

O_NONBLOCK Non-blocking I/O; if no data is available to a read() system call, or if a write() operation would block, the read or write call returns -1 with the error EAGAIN.

Return Values

Upon successful completion, the value returned depends on cmd as follows:
F_GETFL Value of flags.
Other Value other than -1.

The fcntl() system call will fail if:
EBADF The fd argument is not a valid open file descriptor.
EINVAL The specified cmd is invalid.


Versions Link to
INtime 4.0 netlib.lib
See Also