fcntl(5) — PUBLIC FILES, TABLES, AND TROFF MACROS
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 [see fcntl(2)] and open [see 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 | ||
| F_CHKFL | Unused | |
| F_ALLOCSP | Reserved | |
| F_FREESP | Free file space | |
| F_ISSTREAM | Is the file desc. a stream | |
| F_BLOCKS | Get number of BLKSIZE | |
| blocks allocated | ||
| F_BLKSIZE | Get optimal I/O block size | |
| F_RSETLK | Remote SETLK for NFS | |
| F_RGETLK | Remote GETLK for NFS | |
| F_RSETLKW | Remote SETLKW for NFS | |
| F_GETOWN | Get owner (socket emulation, M88000 only) | |
| F_SETOWN | Set owner (socket emulation, M88000 only) | |
| 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_SYNC | Synchronous writes | |
| O_DSYNC | Synchronous data writes (POSIX 1003.4) | |
| O_PRIV | Private access to file | |
| 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:
short l_type; /∗ Type of lock ∗/
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; /∗ Returned with F_GETLK ∗/
short l_sysid; /∗ Returned with F_GETLK ∗/