FGETFD

FGETFD is a system call in Unix-like operating systems that retrieves the file descriptor flags associated with a given file descriptor. File descriptors are small, non-negative integers that represent open files, sockets, or other I/O resources within a process. These flags control various aspects of the file descriptor's behavior, such as whether it is set to non-blocking mode or close-on-exec mode.

The FGETFD system call takes a single argument, the file descriptor for which the flags are to be retrieved. It returns the current flags associated with the file descriptor. The flags are represented as a bitmask, where each bit corresponds to a specific flag. For example, the FD_CLOEXEC flag indicates that the file descriptor should be closed when an exec function is called.

FGETFD is typically used in conjunction with other system calls, such as FSETFD, which sets the file descriptor flags, and FCNTL, which can be used to perform various operations on file descriptors, including getting and setting flags. It is a low-level system call that provides fine-grained control over the behavior of file descriptors, allowing developers to optimize their applications for performance and security.