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MKFIFO(2) System Calls Manual MKFIFO(2)

mkfifo, mkfifoat — make a fifo file

library “libc”

#include <sys/types.h>
#include <sys/stat.h>

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

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

The () system call creates a new fifo file with name path. The access permissions are specified by mode and restricted by the umask(2) of the calling process.

The fifo's owner ID is set to the process's effective user ID. The fifo's group ID is set to that of the parent directory in which it is created.

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

The mkfifo() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

The mkfifo() system call will fail and no fifo will be created if:

[]
The kernel has not been configured to support fifo's.
[]
A component of the path prefix is not a directory.
[]
A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
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A component of the path prefix does not exist.
[]
A component of the path prefix denies search permission, or write permission is denied on the parent directory of the fifo to be created.
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Too many symbolic links were encountered in translating the pathname.
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The named file would reside on a read-only file system.
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The named file exists.
[]
The parent directory of the named file has its immutable flag set, see the chflags(2) manual page for more information.
[]
The directory in which the entry for the new fifo is being placed cannot be extended because there is no space left on the file system containing the directory.
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There are no free inodes on the file system on which the fifo is being created.
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The directory in which the entry for the new fifo is being placed cannot be extended because the user's quota of disk blocks on the file system containing the directory has been exhausted.
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The user's quota of inodes on the file system on which the fifo is being created has been exhausted.
[]
An I/O error occurred while making the directory entry or allocating the inode.
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An I/O error occurred while reading from or writing to the file system.
[]
The path argument points outside the process's allocated address space.

In addition to the errors returned by the mkfifo(), the mkfifoat() may fail if:

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The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
[]
The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

chflags(2), chmod(2), mknod(2), stat(2), umask(2)

The mkfifo() system call is expected to conform to IEEE Std 1003.1-1990 (“POSIX.1”). The mkfifoat() system call follows The Open Group Extended API Set 2 specification.

The mkfifoat() system call appeared in FreeBSD 8.0.

April 10, 2008 FreeBSD-12.0