Fcntl - various flag constants and helper functions from C's fcntl.h
use Fcntl;
use Fcntl qw(:DEFAULT :flock);
use Fcntl qw(F_GETFD F_SETFD FD_CLOEXEC);
This module provides flags and helper functions for use with "chmod" in perlfunc (S_*), "fcntl" in perlfunc (F_*), "flock" in perlfunc (LOCK_*), "seek" in perlfunc (SEEK_*), "stat" in perlfunc (S_*), "sysopen" in perlfunc (O_*), and "sysseek" in perlfunc (SEEK_*). They correspond to the C macros defined in fcntl.h.
Not all symbols are available on all systems. Except where noted otherwise, the constants and functions provided by this module will throw a runtime exception if the corresponding C macro is not available. Consult your system documentation to see the full description of each symbol and whether it is available on your platform: chmod(2), fcntl(2), flock(2), lseek(2), open(2), stat(2).
(In particular, some of the F_* symbols are highly non-portable because they only exist on a single platform or require system-specific C data structures to be passed as the third argument to fcntl
, which can't be portably constructed in pure Perl.)
The full list of default exports can be found below in "APPENDIX A".
In addition, the following export tags are available (see Exporter for more information on export tags):
:DEFAULT
Equivalent to the list of default export symbols (see "APPENDIX A").
:flock
Equivalent to all LOCK_* symbols listed below.
:mode
Equivalent to all S_* symbols listed below.
:seek
Equivalent to all SEEK_* symbols listed below.
:Fcompat
Equivalent to qw(FAPPEND FASYNC FCREAT FDEFER FDSYNC FEXCL FLARGEFILE FNDELAY FNONBLOCK FRSYNC FSYNC FTRUNC)
. These only exist for compatibility with old code (if your platform defines them at all) and should not be used in new code.
fcntl
F_ALLOCSP
File storage manipulation.
F_ALLOCSP64
File storage manipulation.
F_DUP2FD
Duplicate a file descriptor to the number specified in the third argument to fcntl
(if it refers to an open file, it is automatically closed first).
F_DUPFD
Duplicate a file descriptor to the lowest unused number greater than or equal to the third argument of fcntl
.
F_FREESP
File storage manipulation.
F_FREESP64
File storage manipulation.
F_FSYNC
Synchronize file data to disk.
F_FSYNC64
Synchronize file data to disk.
F_GETFD
Return (as a number) the set of file descriptor flags, in which the following bits may be set:
FD_CLOEXEC
During a successful exec
call, the file descriptor will be closed automatically.
F_GETFL
Return (as a number) the set of file description status flags (O_*) as set by open
and fcntl
. To determine the file access mode, perform a bitwise AND with "O_ACCMODE
" and see whether the result is equal to O_RDONLY
, O_WRONLY
, or O_RDWR
.
F_GETLEASE
Indicate the type of lease associated with the filehandle (if any) by returning one of the following flags:
F_GETLK
Test for the existence of record locks on the file.
F_GETLK64
Test for the existence of record locks on the file.
F_GETOWN
Return the ID of the process (as a positive number) or group (as a negative number) that is currently receiving signals for events on the file descriptor.
F_GETPIPE_SZ
Return the capacity of the pipe associated with the filehandle.
F_GETSIG
Return the number of the signal sent when input or output becomes possible on the filehandle. A return value of 0
means SIGIO
.
F_NOTIFY
File and directory change notification with signals.
F_SETFD
Set the file descriptor flags. See "F_GETFD
" for the list of available flags.
F_SETFL
Set the file description status flags (O_*). Only some flags can be changed this way.
F_SETLEASE
Set a file lease as specified by the third fnctl
argument, which must be one of the following:
F_SETLK
Acquire a record lock.
F_SETLK64
Acquire a record lock.
F_SETLKW
Acquire a record lock and wait for conflicting locks to be released.
F_SETLKW64
Acquire a record lock and wait for conflicting locks to be released.
F_SETOWN
Set the ID of the process (as a positive number) or group (as a negative number) that will receive signals for events on the file descriptor.
F_SETPIPE_SZ
Set the capacity of the pipe associated with the filehandle. Return the actual capacity reserved for the pipe, which may be higher than requested.
F_SETSIG
Set the number of the signal sent when input or output becomes possible on the filehandle. An argument of 0
means SIGIO
.
F_SHARE
Set share reservation.
F_UNSHARE
Remove share reservation.
F_COMPAT
F_EXLCK
F_NODNY
F_POSIX
F_RDACC
F_RDDNY
F_RWACC
F_RWDNY
F_SHLCK
F_WRACC
F_WRDNY
flock
LOCK_EX
Request an exclusive lock.
LOCK_MAND
Request a mandatory lock.
LOCK_NB
Make lock request non-blocking (can be combined with other LOCK_* flags using bitwise OR).
LOCK_READ
With LOCK_MAND
: Allow concurrent reads.
LOCK_RW
With LOCK_MAND
: Allow concurrent reads and writes.
LOCK_SH
Request a shared lock.
LOCK_UN
Release a held lock.
LOCK_WRITE
With LOCK_MAND
: Allow concurrent writes.
sysopen
O_ACCMODE
Bit mask for extracting the file access mode (read-only, write-only, or read/write) from the other flags. This is mainly useful in combination with "F_GETFL
".
O_ALIAS
(Mac OS) Open alias file (instead of the file that the alias refers to).
O_ALT_IO
(NetBSD) Use alternative I/O semantics.
O_APPEND
Open the file in append mode. Writes always go to the end of the file.
O_ASYNC
Enable signal-based I/O. When the file becomes readable or writable, a signal is sent.
O_BINARY
(Windows) Open the file in binary mode.
O_CREAT
If the file to be opened does not exist yet, create it.
O_DEFER
(AIX) Changes to the file are kept in memory and not written to disk until the program performs an explicit $fh->sync()
.
O_DIRECT
Perform direct I/O to/from user-space buffers; avoid caching at the OS level.
O_DIRECTORY
Fail if the filename to be opened does not refer to a directory.
O_DSYNC
Synchronize file data immediately, like calling fdatasync(2) after each write.
O_EVTONLY
(Mac OS) Open the file for event notifications, not reading or writing.
O_EXCL
If the file already exists, fail and set $!
to EEXIST
(this only makes sense in combination with O_CREAT
).
O_EXLOCK
When the file is opened, atomically obtain an exclusive lock.
O_IGNORE_CTTY
(Hurd) If the file to be opened is the controlling terminal for this process, don't recognize it as such. Operations on this filehandle won't trigger job control signals.
O_LARGEFILE
On 32-bit platforms, allow opening files whose size exceeds 2 GiB (2,147,483,647 bytes).
O_NDELAY
Compatibility symbol. Use O_NONBLOCK
instead.
O_NOATIME
Don't update the access time of the file when reading from it.
O_NOCTTY
If the process does not have a controlling terminal and the file to be opened is a terminal device, don't make it the controlling terminal of the process.
O_NOFOLLOW
If the final component of the filename is a symbolic link, fail and set $!
to ELOOP
.
O_NOINHERIT
(Windows) Don't let child processes inherit the opened file descriptor.
O_NOLINK
(Hurd) If the file to be opened is a symbolic link, don't follow it; open the link itself.
O_NONBLOCK
Open the file in non-blocking mode. Neither the open itself nor any read/write operations on the filehandle will block. (This is mainly useful for pipes and sockets. It has no effect on regular files.)
O_NOSIGPIPE
If the file to be opened is a pipe, then don't raise SIGPIPE
for write operations when the read end of the pipe is closed; make the write fail with EPIPE
instead.
O_NOTRANS
(Hurd) If the file to be opened is specially translated, don't invoke the translator; open the bare file itself.
O_RANDOM
(Windows) Indicate that the program intends to access the file contents randomly (without a predictable pattern). This is an optimization hint for the file cache (but may cause excessive memory use on large files).
O_RAW
(Windows) Same as O_BINARY
.
O_RDONLY
Open the file for reading (only).
O_RDWR
Open the file for reading and writing.
O_RSRC
(Mac OS) Open the resource fork of the file.
O_RSYNC
Extend the effects of O_SYNC
and O_DSYNC
to read operations. In particular, reading from a filehandle opened with O_SYNC | O_RSYNC
will wait until the access time of the file has been modified on disk.
O_SEQUENTIAL
(Windows) Indicate that the program intends to access the file contents sequentially. This is an optimization hint for the file cache.
O_SHLOCK
When the file is opened, atomically obtain a shared lock.
O_SYMLINK
If the file to be opened is a symbolic link, don't follow it; open the link itself.
O_SYNC
Synchronize file data and metadata immediately, like calling fsync(2) after each write.
O_TEMPORARY
(Windows) Delete the file when its last open file descriptor is closed.
O_TEXT
(Windows) Open the file in text mode.
O_TMPFILE
Create an unnamed temporary file. The filename argument specifies the directory the unnamed file should be placed in.
O_TRUNC
If the file already exists, truncate its contents to length 0.
O_TTY_INIT
If the file to be opened is a terminal that is not already open in any process, initialize its termios parameters.
O_WRONLY
Open the file for writing (only).
FAPPEND
Compatibility symbol. Use O_APPEND
instead.
FASYNC
Compatibility symbol. Use O_ASYNC
instead.
FCREAT
Compatibility symbol. Use O_CREAT
instead.
FDEFER
Compatibility symbol. Use O_DEFER
instead.
FDSYNC
Compatibility symbol. Use O_DSYNC
instead.
FEXCL
Compatibility symbol. Use O_EXCL
instead.
FLARGEFILE
Compatibility symbol. Use O_LARGEFILE
instead.
FNDELAY
Compatibility symbol. Use O_NDELAY
instead.
FNONBLOCK
Compatibility symbol. Use O_NONBLOCK
instead.
FRSYNC
Compatibility symbol. Use O_RSYNC
instead.
FSYNC
Compatibility symbol. Use O_SYNC
instead.
FTRUNC
Compatibility symbol. Use O_TRUNC
instead.
seek
and sysseek
SEEK_CUR
File offsets are relative to the current position in the file.
SEEK_END
File offsets are relative to the end of the file (i.e. mostly negative).
SEEK_SET
File offsets are absolute (i.e. relative to the beginning of the file).
stat
and chmod
S_ENFMT
Enforce mandatory file locks. (This symbol typically shares its value with S_ISGID
.)
S_IEXEC
Compatibility symbol. Use S_IXUSR
instead.
S_IFBLK
File type: Block device.
S_IFCHR
File type: Character device.
S_IFDIR
File type: Directory.
S_IFIFO
File type: Fifo/pipe.
S_IFLNK
File type: Symbolic link.
S_IFMT
Bit mask for extracting the file type bits. This symbol can also be used as a function: S_IFMT($mode)
acts like $mode & S_IFMT
. The result will be equal to one of the other S_IF* constants.
_S_IFMT
Bit mask for extracting the file type bits. This symbol is an actual constant and cannot be used as a function; otherwise it is identical to S_IFMT
.
S_IFREG
File type: Regular file.
S_IFSOCK
File type: Socket.
S_IFWHT
File type: Whiteout file (used to mark the absence/deletion of a file in overlays).
S_IMODE
Function for extracting the permission bits from a file mode.
S_IREAD
Compatibility symbol. Use S_IRUSR
instead.
S_IRGRP
Permissions: Readable by group.
S_IROTH
Permissions: Readable by others.
S_IRUSR
Permissions: Readable by owner.
S_IRWXG
Bit mask for extracting group permissions.
S_IRWXO
Bit mask for extracting other permissions.
S_IRWXU
Bit mask for extracting owner ("user") permissions.
S_ISBLK
Convenience function to check for block devices: S_ISBLK($mode)
is equivalent to S_IFMT($mode) == S_IFBLK
.
S_ISCHR
Convenience function to check for character devices: S_ISCHR($mode)
is equivalent to S_IFMT($mode) == S_IFCHR
.
S_ISDIR
Convenience function to check for directories: S_ISDIR($mode)
is equivalent to S_IFMT($mode) == S_IFDIR
.
S_ISFIFO
Convenience function to check for fifos: S_ISFIFO($mode)
is equivalent to S_IFMT($mode) == S_IFIFO
.
S_ISGID
Permissions: Set effective group ID from file (when running executables); mandatory locking (on non-group-executable files); new files inherit their group from the directory (on directories).
S_ISLNK
Convenience function to check for symbolic links: S_ISLNK($mode)
is equivalent to S_IFMT($mode) == S_IFLNK
.
S_ISREG
Convenience function to check for regular files: S_ISREG($mode)
is equivalent to S_IFMT($mode) == S_IFREG
.
S_ISSOCK
Convenience function to check for sockets: S_ISSOCK($mode)
is equivalent to S_IFMT($mode) == S_IFSOCK
.
S_ISTXT
Compatibility symbol. Use S_ISVTX
instead.
S_ISUID
Permissions: Set effective user ID from file (when running executables).
S_ISVTX
Permissions: Files in this directory can only be deleted/renamed by their owner (or the directory's owner), even if other users have write permissions to the directory ("sticky bit").
S_ISWHT
Convenience function to check for whiteout files: S_ISWHT($mode)
is equivalent to S_IFMT($mode) == S_IFWHT
.
S_IWGRP
Permissions: Writable by group.
S_IWOTH
Permissions: Writable by others.
S_IWRITE
Compatibility symbol. Use S_IWUSR
instead.
S_IWUSR
Permissions: Writable by owner.
S_IXGRP
Permissions: Executable/searchable by group.
S_IXOTH
Permissions: Executable/searchable by others.
S_IXUSR
Permissions: Executable/searchable by owner.
"chmod" in perlfunc, chmod(2), "fcntl" in perlfunc, fcntl(2), "flock" in perlfunc, flock(2), "seek" in perlfunc, fseek(3), "stat" in perlfunc, stat(2), "sysopen" in perlfunc, open(2), "sysseek" in perlfunc, lseek(2)
By default, if you say use Fcntl;
, the following symbols are exported:
FD_CLOEXEC
F_ALLOCSP
F_ALLOCSP64
F_COMPAT
F_DUP2FD
F_DUPFD
F_EXLCK
F_FREESP
F_FREESP64
F_FSYNC
F_FSYNC64
F_GETFD
F_GETFL
F_GETLK
F_GETLK64
F_GETOWN
F_NODNY
F_POSIX
F_RDACC
F_RDDNY
F_RDLCK
F_RWACC
F_RWDNY
F_SETFD
F_SETFL
F_SETLK
F_SETLK64
F_SETLKW
F_SETLKW64
F_SETOWN
F_SHARE
F_SHLCK
F_UNLCK
F_UNSHARE
F_WRACC
F_WRDNY
F_WRLCK
O_ACCMODE
O_ALIAS
O_APPEND
O_ASYNC
O_BINARY
O_CREAT
O_DEFER
O_DIRECT
O_DIRECTORY
O_DSYNC
O_EXCL
O_EXLOCK
O_LARGEFILE
O_NDELAY
O_NOCTTY
O_NOFOLLOW
O_NOINHERIT
O_NONBLOCK
O_RANDOM
O_RAW
O_RDONLY
O_RDWR
O_RSRC
O_RSYNC
O_SEQUENTIAL
O_SHLOCK
O_SYNC
O_TEMPORARY
O_TEXT
O_TRUNC
O_WRONLY