mkfifo

, mkfifoat

- make a FIFO special file

Synopsis

#include <sys/stat.h>

int mkfifo(const char *path, mode_t mode);

int mkfifoat(int fd, const char *path, mode_t mode);

Description

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.

If path names a symbolic link, mkfifo() fails and sets errno to EEXIST.

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.

The mkfifoat() function is equivalent to mkfifo() except in the case where path specifies a relative path. In this case the newly created FIFO is created relative to the directory associated with the file descriptor fd instead of the current working directory. If the file descriptor was opened without O_SEARCH, the function checks whether directory searches are permitted using the current permissions of the directory underlying the file descriptor. If the file descriptor was opened with O_SEARCH, the function does not perform the check

If mkfifoat() is passed the special value AT_FDCWD in the fd parameter, the current working directory is used and the is be identical to a call to mkfifo().

Return Values

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

Errors

The mkfifo() and mkfifoat() functions 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 mkfifoat() functions will fail if:

EACCES

fd was not opened with O_SEARCH and the permissions of the directory underlying fd do not permit directory searches.

EBADF

The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for reading or searching.

The mkfifo() and mkfifoat() functions may fail if:

ELOOP

Too many symbolic links were encountered in resolving path.

ENAMETOOLONG

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

The mkfifoat() functions may fail if:

ENOTDIR

The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

Examples

Example 1 Create a FIFO File

The following example demonstrates how to create a FIFO file named /home/cnd/mod_done with read and write permissions for the owner and read permissions for the group and others.

#include sys/stat.h>
int status;
...
status = mkfifo("/home/cnd/mod_done", S_IWUSR | S_IRUSR |
        S_IRGRP | S_IROTH);

Attributes

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

See Also

mkdir(1), chmod(2), exec(2), mknod(2), umask(2), stat.h(3HEAD), ufs(7FS), attributes(5), standards(5)