mkfifo(3)

💅 mkfifo(3) — bestie edition

okay so. this is the mkfifo(3) page from the Library Functions Manual, and it's literally about making named pipes. yes, the manual name is right there in the title, we move on 🫶

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✨ NAME ✨

mkfifo, mkfifoat — make a FIFO special file (a named pipe)

📚 LIBRARY 📚

Standard C library (libc, -lc)

🌸 SYNOPSIS 🌸

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

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

#include <fcntl.h>           /* Definition of AT_* constants */
#include <sys/stat.h>

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

🧚 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

mkfifoat():
    Since glibc 2.10:
        _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _ATFILE_SOURCE

💖 DESCRIPTION 💖

So mkfifo() makes a FIFO special file with name path. and mode is what sets the FIFO's permissions. ngl it gets modified by the process's umask the usual way, so the permissions of the created file are literally (mode & ~umask). the math is mathing 💅

A FIFO special file is like a pipe, except it gets created differently. instead of being an anonymous communications channel, a FIFO special file gets entered into the filesystem when you call mkfifo(). it's giving glow-up, honestly ✨

Once you've created a FIFO special file like this, any process can open it for reading or writing, same as an ordinary file. HOWEVER — plot twist 😭 — it has to be open at both ends simultaneously before you can proceed to do any input or output operations on it. Opening a FIFO for reading normally blocks until some other process opens the same FIFO for writing, and vice versa. so like, don't just stand there bestie. check fifo(7) for nonblocking handling of FIFO special files, iykyk.

🦋 mkfifoat() 🦋

mkfifoat() operates in exactly the same way as mkfifo(), except for the differences described here. and the differences are:

• If path is relative, then it's interpreted relative to the directory referred to by the file descriptor dirfd (rather than relative to the current working directory of the calling process, as is done by mkfifo() for a relative pathname).
• If path is relative and dirfd is the special value AT_FDCWD, then path is interpreted relative to the current working directory of the calling process (like mkfifo()).
• If path is absolute, then dirfd is ignored. periodt.

See openat(2) for an explanation of the need for mkfifoat().

🎀 RETURN VALUE 🎀

On success, mkfifo() and mkfifoat() return 0. that's the slay. 🥳

On error, -1 is returned and errno is set to indicate the error. the vibe check failed bestie 💀

🔥 ERRORS 🔥

• EACCES — one of the directories in path did not allow search (execute) permission. rude.
• EBADF — (mkfifoat()) path is relative but dirfd is neither AT_FDCWD nor a valid file descriptor.
• EDQUOT — the user's quota of disk blocks or inodes on the filesystem has been exhausted. no more room, no more slay.
• EEXIST — path already exists. and yes, this includes the case where path is a symbolic link, dangling or not. iconic behavior, honestly.
• ENAMETOOLONG — either the total size of path is greater than PATH_MAX, or an individual filename component has a length greater than NAME_MAX. In the GNU system, there is no imposed limit on overall filename length, but some filesystems may place limits on the length of a component.
• ENOENT — a directory component in path does not exist or is a dangling symbolic link. she's not home 💔
• ENOSPC — the directory or filesystem has no room for the new file.
• ENOTDIR — a component used as a directory in path is not, in fact, a directory.
• ENOTDIR — (mkfifoat()) path is relative and dirfd is a file descriptor referring to a file other than a directory. yes this one shows up twice in the original, we don't make the rules 💅
• EROFS — path refers to a read-only filesystem. read-only era, respect it.

👑 ATTRIBUTES 👑

For an explanation of the terms used in this section, see attributes(7).

• Interface: mkfifo(), mkfifoat()
• Attribute: Thread safety
• Value: MT-Safe

(that's the whole table, she's small but mighty 🫶)

⭐ VERSIONS ⭐

It is implemented using mknodat(2). lowkey that's the whole tea.

🌈 STANDARDS 🌈

POSIX.1-2008.

📜 HISTORY 📜

• mkfifo() — POSIX.1-2001.
• mkfifoat() — glibc 2.4. POSIX.1-2008.

💜 SEE ALSO 💜

mkfifo(1), close(2), open(2), read(2), stat(2), umask(2), write(2), fifo(7)

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that's the whole page bestie, go make some pipes 💖

signing off with the receipts: this is from Linux man-pages 6.20, dated 2026-02-08, and the page name up top was mkfifo(3). no cap, not one detail dropped. mwah 😘