File Descriptor and I/O Control

fcntl

Supported functionality in SCML:

ignore_flags = O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC;
can_change_flags = O_APPEND | O_ASYNC | O_DIRECT | O_NOATIME | O_NONBLOCK;

// Duplicate a file descriptor
fcntl(fd, cmd = F_DUPFD | F_DUPFD_CLOEXEC, arg);

// Retrieve file descriptor flags (F_GETFD), file status flags (F_GETFL)
// or SIGIO/SIGURG owner process (F_GETOWN)
fcntl(fd, cmd = F_GETFD | F_GETFL | F_GETOWN);

// Set file descriptor flags
fcntl(fd, cmd = F_SETFD, arg = FD_CLOEXEC);

// Set file status flags
fcntl(fd, cmd = F_SETFL, arg = <ignore_flags> | <can_change_flags>);

// Manage record locks: test (F_GETLK), non-blocking set (F_SETLK), blocking set (F_SETLKW)
fcntl(fd, cmd = F_GETLK | F_SETLK | F_SETLKW, arg);

// Assign SIGIO/SIGURG owner process
fcntl(fd, cmd = F_SETOWN, arg);

Unsupported commands:

• F_NOTIFY
• F_OFD_SETLK, F_OFD_SETLKW and F_OFD_GETLK
• F_GETOWN_EX and F_SETOWN_EX
• F_GETSIG and F_SETSIG
• F_SETLEASE and F_GETLEASE
• F_SETPIPE_SZ and F_GETPIPE_SZ
• F_ADD_SEALS and F_GET_SEALS
• F_GET_RW_HINT and F_SET_RW_HINT
• F_GET_FILE_RW_HINT and F_SET_FILE_RW_HINT

For more information, see the man page.

pipe and pipe2

Supported functionality in SCML:

// Create pipe
pipe(pipefd);

// Create pipe with enhanced behavior control
pipe2(pipefd, flags = O_CLOEXEC);

Silently-ignored flags:

• O_DIRECT
• O_NONBLOCK

For more information, see the man page.

eventfd and eventfd2

Supported functionality in SCML:

// Create event notification descriptor
eventfd(initval);

// Create event notification descriptor with enhanced behavior control
eventfd2(initval, flags = EFD_CLOEXEC);

Silently-ignored flags:

• EFD_NONBLOCK
• EFD_SEMAPHORE

For more information, see the man page.