Fcntl#

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Symbolic constants for fcntl(2), flock(2), seek(2), and file-mode bits - everything you need to call sysopen, fcntl, flock, seek, and to interpret the mode word returned by stat.

Import individual names, or a named group via one of the export tags: :DEFAULT (open and file-descriptor flags), :flock (advisory locks), :seek (whence positions), :mode (mode bits and S_IS* predicates), :Fcompat (BSD-style flock aliases).

Open flags (sysopen)#

  • O_RDONLY, O_WRONLY, O_RDWR - access mode.

  • O_CREAT - create the file if it does not exist.

  • O_EXCL - with O_CREAT, fail if the file already exists.

  • O_TRUNC - truncate to zero length on open.

  • O_APPEND - every write seeks to end of file first.

  • O_NONBLOCK - open without blocking; I/O returns EAGAIN instead.

  • O_NOCTTY, O_NOFOLLOW, O_BINARY - additional platform flags (O_BINARY is a no-op on Linux).

File-descriptor control (fcntl)#

  • F_DUPFD - duplicate a descriptor.

  • F_GETFD, F_SETFD - read / set the close-on-exec flag FD_CLOEXEC.

  • F_GETFL, F_SETFL - read / set the open-file status flags.

Lock types (flock)#

  • LOCK_SH - shared lock.

  • LOCK_EX - exclusive lock.

  • LOCK_UN - release lock.

  • LOCK_NB - OR with the above to request a non-blocking attempt.

Seek whence#

  • SEEK_SET - from start of file.

  • SEEK_CUR - from current position.

  • SEEK_END - from end of file.

File mode bits (stat)#

  • Type mask and values: S_IFMT, S_IFREG, S_IFDIR, S_IFCHR, S_IFBLK, S_IFIFO, S_IFLNK, S_IFSOCK.

  • Permission triplets: S_IRWXU, S_IRWXG, S_IRWXO and the per-bit S_IRUSR / S_IWUSR / S_IXUSR (and the GRP, OTH variants).

  • Setuid / setgid / sticky bits: S_ISUID, S_ISGID, S_ISVTX.

Mode test helpers#

Function-form predicates over a stat-mode value: S_ISREG, S_ISDIR, S_ISCHR, S_ISBLK, S_ISFIFO, S_ISLNK, S_ISSOCK, plus S_IFMT (extract file-type bits) and S_IMODE (extract permission bits).

ביצועים#

Every constant in this module is resolved at compile time - using O_CREAT in an expression costs exactly what writing the integer literal would cost. No per-call lookup.

Functions#

Mode test helpers#

s_ifmt#

Extract the file-type bits from a stat-mode value.

s_imode#

Extract the permission bits from a stat-mode value.

s_isreg#

True if a stat-mode value names a regular file.

s_isdir#

True if a stat-mode value names a directory.

s_ischr#

True if a stat-mode value names a character-special device.

s_isblk#

True if a stat-mode value names a block-special device.

s_isfifo#

True if a stat-mode value names a named pipe (FIFO).

s_islnk#

True if a stat-mode value names a symbolic link.

s_issock#

True if a stat-mode value names a socket.