F_GETFD2const
Get/set file descriptor flags
Usage
#include <fcntl.h>
int fcntl(int fd, F_GETFD); int fcntl(int fd, F_SETFD, int arg);
Library
Standard C library (libc, -lc)
Overview
These operations manipulate the flags associated with a file descriptor. Currently, only one such flag is defined: FD_CLOEXEC, the close-on-exec flag. If the FD_CLOEXEC bit is set, the file descriptor will automatically be closed during a successful execve(2). (If the execve(2) fails, the file descriptor is left open.) If the FD_CLOEXEC bit is not set, the file descriptor will remain open across an execve(2).
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Return (as the function result) the file descriptor flags; arg is ignored. |
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Set the file descriptor flags to the value specified by arg. |
Return value
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Value of file descriptor flags. |
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Zero. |
On error, -1 is returned, and errno is set to indicate the error.
Errors
See fcntl(2).
Caveats
In multithreaded programs, using fcntl(2) F_SETFD to set the close-on-exec flag at the same time as another thread performs a fork(2) plus execve(2) is vulnerable to a race condition that may unintentionally leak the file descriptor to the program executed in the child process. See the discussion of the O_CLOEXEC flag in open(2) for details and a remedy to the problem.