The mkfifo() function creates a new FIFO special file named by the pathname pointed to by path. The file permission bits of the new FIFO are initialized from mode. The file permission bits of the mode argument are modified by the process's file creation mask (see umask(2)). Bits other than the file permission bits in mode are ignored.

The FIFO's user ID is set to the process's effective user ID. The FIFO's group ID is set to the group ID of the parent directory or to the effective group ID of the process.

The mkfifo() function calls mknod(2) to create the file.

Upon successful completion, mkfifo() marks for update the st_atime, st_ctime, and st_mtime fields of the file. Also, the st_ctime and st_mtime fields of the directory that contains the new entry are marked for update.

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

The mkfifo() function will fail if:

EACCES

A component of the path prefix denies search permission, or write permission is denied on the parent directory of the FIFO to be created.

EEXIST

The named file already exists.

ELOOP

A loop exists in symbolic links encountered during resolution of the path argument.

ENAMETOOLONG

The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

ENOENT

A component of the path prefix specified by path does not name an existing directory or path is an empty string.

ENOSPC

The directory that would contain the new file cannot be extended or the file system is out of file-allocation resources.

ENOTDIR

A component of the path prefix is not a directory.

EROFS

The named file resides on a read-only file system.

The mkfifo() function may fail if:

ELOOP

More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.

See attributes(5) for descriptions of the following attributes:

mkdir(1), chmod(2), exec(2), mknod(2), umask(2), stat(3HEAD), fs_ufs(4), attributes(5)