fcntl(5)
NAME
fcntl − file control options
SYNOPSIS
#include <fcntl.h>
DESCRIPTION
The <fcntl.h> header defines the following requests and arguments for use by the functions fcntl(2) and open(2).
| Values for cmd used by fcntl (the following values are unique): | ||
| F_DUPFD | Duplicate file descriptor | |
| F_GETFD | Get file descriptor flags | |
| F_SETFD | Set file descriptor flags | |
| F_GETFL | Get file status flags | |
| 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 | ||
| File descriptor flags used for fcntl: | ||
| FD_CLOEXEC | Close the file descriptor upon | |
| execution of an exec function (see exec(2)) | ||
| Values for l_type used for record locking with fcntl | ||
| (the following values are unique): | ||
| F_RDLCK | Shared or read lock | |
| F_UNLCK | Unlock | |
| F_WRLCK | Exclusive or write lock | |
| The following three sets of values are bitwise distinct: | ||
| Values for oflag used by open | ||
| O_CREAT | Create file if it does not exist | |
| O_EXCL | Exclusive use flag | |
| O_NOCTTY | Do not assign controlling tty | |
| O_TRUNC | Truncate flag | |
| File status flags used for open and fcntl: | ||
| O_APPEND | Set append mode | |
| O_NDELAY | Non-blocking mode | |
| O_NONBLOCK | Non-blocking mode (POSIX) | |
| O_DSYNC | Write I/O operations on the file descriptor complete | |
| as defined by synchronized I/O data integrity completion | ||
| O_RSYNC | Read I/O operations on the file descriptor complete at the | |
| same level of integrity as specified by the the O_DSYNC | ||
| and O_SYNC flags. If both O_DSYNC and O_RSYNC are set | ||
| in oflag, all I/O operations on the file descriptor complete as | ||
| defined by synchronized I/O data integrity completion. If both | ||
| O_SYNC and O_RSYNC are set in oflag, all I/O operations on | ||
| the file descriptor complete as defined by synchronized I/O file | ||
| integrity completion. | ||
| O_SYNC | When opening a regular file, this flag affects subsequent writes. | |
| If set, each write (2) will wait for both the file data and | ||
| file status to be physically updated. Write I/O operations on the | ||
| file descriptor complete as defined by synchronized I/O file | ||
| integrity completion. | ||
| Mask for use with file access modes: | ||
| O_ACCMODE | Mask for file access modes |
|
| File access modes used for open and fcntl: | ||
| O_RDONLY | Open for reading only | |
| O_RDWR | Open for reading and writing | |
| O_WRONLY | Open for writing only | |
The structure flock describes a file lock. It includes the following members:
shortl_type;/∗ Type of lock ∗/
shortl_whence;/∗ Flag for starting offset ∗/
off_tl_start;/∗ Relative offset in bytes ∗/
off_tl_len;/∗ Size; if 0 then until EOF ∗/
longl_sysid;/∗ Returned with F_GETLK ∗/
pid_tl_pid;/∗ Returned with F_GETLK ∗/
SEE ALSO
creat(2), exec(2), fcntl(2), open(2), fsync(3C), fdatasync(3R)
NOTES
Data is successfully transferred for a write operation to a regular file when the system ensures that all data written is readable on any subsequent open of the file (even one that follows a system or power failure) in the absense of a failure of the physical storage medium.
Data is successfully transferred for a read operation when an image of the data on the physical storage medium is available to the requesting process.
Synchronized I/O data integrity completion (see fdatasync(3R)):
For reads, the operation has been completed or diagnosed if unsuccessful. The read is complete only when an image of the data has been successfully transferred to the requesting process. If there were any pending write requests affecting the data to be read at the time that the synchronized read operation was requested, these write requests will be successfully transferred prior to reading the data.
For writes, the operation has been completed or diagnosed if unsuccessful. The write is complete only when the data specified in the write request is successfully transferred, and all file system information required to retrieve the data is successfully transferred.
File attributes that are not necessary for data retrieval (access time, modification time, status change time) need not be successfully transferred prior to returning to the calling process.
Synchronized I/O file integrity completion (see fsync(3C)):
Identical to a synchronized I/O data integrity completion with the addition that all file attributes relative tothe I/O operation (including access time, modification time, status change time) will be successfully transferred prior to returning to the calling process.
Sun Microsystems — Last change: 3 Jul 1990