<fcntl.h>(P) POSIX Programmer s Manual <fcntl.h>(P)

PROLOG This manual page is part of the POSIX Programmer s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME fcntl.h - file control options

SYNOPSIS #include <fcntl.h>

DESCRIPTION The <fcntl.h> header shall define the following requests and arguments for use by the functions fcntl() and open().

Values for cmd used by fcntl() (the following values are unique) are as follows:

F_DUPFD Duplicate file descriptor.

F_GETFD Get file descriptor flags.

F_SETFD Set file descriptor flags.

F_GETFL Get file status flags and file access modes.

F_SETFL Set file status flags.

F_GETLK Get record locking information.

F_SETLK Set record locking information.

F_SETLKW Set record locking information; wait if blocked.

F_GETOWN Get process or process group ID to receive SIGURG signals.

F_SETOWN Set process or process group ID to receive SIGURG signals.

File descriptor flags used for fcntl() are as follows:

FD_CLOEXEC Close the file descriptor upon execution of an exec family func- tion.

Values for l_type used for record locking with fcntl() (the following values are unique) are as follows:

F_RDLCK Shared or read lock.

F_UNLCK Unlock.

F_WRLCK Exclusive or write lock.

The values used for l_whence, SEEK_SET, SEEK_CUR, and SEEK_END shall be defined as described in <unistd.h> .

The following values are file creation flags and are used in the oflag value to open(). They shall be bitwise-distinct.

O_CREAT Create file if it does not exist.

O_EXCL Exclusive use flag.

O_NOCTTY Do not assign controlling terminal.

O_TRUNC Truncate flag.

File status flags used for open() and fcntl() are as follows:

O_APPEND Set append mode.

O_DSYNC Write according to synchronized I/O data integrity completion.

O_NONBLOCK Non-blocking mode.

O_RSYNC Synchronized read I/O operations.

O_SYNC Write according to synchronized I/O file integrity completion.

Mask for use with file access modes is as follows:

O_ACCMODE Mask for file access modes.

File access modes used for open() and fcntl() are as follows:

O_RDONLY Open for reading only.

O_RDWR Open for reading and writing.

O_WRONLY Open for writing only.

The symbolic names for file modes for use as values of mode_t shall be defined as described in <sys/stat.h> .

Values for advice used by posix_fadvise() are as follows:

POSIX_FADV_NORMAL

The application has no advice to give on its behavior with respect to the specified data. It is the default characteristic if no advice is given for an open file.

POSIX_FADV_SEQUENTIAL

The application expects to access the specified data sequen- tially from lower offsets to higher offsets.

POSIX_FADV_RANDOM

The application expects to access the specified data in a random order.

POSIX_FADV_WILLNEED

The application expects to access the specified data in the near future.

POSIX_FADV_DONTNEED

The application expects that it will not access the specified data in the near future.

POSIX_FADV_NOREUSE

The application expects to access the specified data once and then not reuse it thereafter.

The structure flock describes a file lock. It shall include the follow- ing members:

short l_type Type of lock; F_RDLCK, F_WRLCK, F_UNLCK. short l_whence Flag for starting offset. off_t l_start Relative offset in bytes. off_t l_len Size; if 0 then until EOF. pid_t l_pid Process ID of the process holding the lock; returned with F_GETLK.

The mode_t, off_t, and pid_t types shall be defined as described in <sys/types.h> .

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

int creat(const char *, mode_t); int fcntl(int, int, ...); int open(const char *, int, ...);

int posix_fadvise(int, off_t, size_t, int); int posix_fallocate(int, off_t, size_t);

Inclusion of the <fcntl.h> header may also make visible all symbols from <sys/stat.h> and <unistd.h>.

The following sections are informative.

APPLICATION USAGE None.

RATIONALE None.

FUTURE DIRECTIONS None.

SEE ALSO <sys/stat.h> , <sys/types.h> , <unistd.h> , the System Interfaces vol- ume of IEEE Std 1003.1-2001, creat(), exec, fcntl(), open(), posix_fad- vise(), posix_fallocate(), posix_madvise()

COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group 2003 <fcntl.h>(P)