MKFIFO(2) System Calls Manual MKFIFO(2)

mkfifo, mkfifoat — make a fifo file

#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);

() 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 file 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().

A 0 return value indicates success. A -1 return value indicates an error, and an error code is stored in errno.

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

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The kernel has not been configured to support fifo's.
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A component of the path prefix is not a directory.
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A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
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A component of the path prefix does not exist.
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Search permission is denied for a component of the path prefix.
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Too many symbolic links were encountered in translating the pathname.
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The named file resides on a read-only file system.
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The named file exists.
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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.
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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.
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Path points outside the process's allocated address space.
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The filename does not match the encoding rules.

In addition to the errors returned by the mkfifo(), the mkfifoat() function 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.
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The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

chmod(2), stat(2), umask(2)

The mkfifo function call conforms to IEEE Std 1003.1-1988 (“POSIX.1”).

June 4, 1993 macOS 15.2