PIPE(3)

💖 PIPE(3) — Library Functions Manual 💖

okay bestie, welcome to the pipe page, this is PIPE(3) from the Library Functions Manual and honestly it's giving "small function, chaotic lore" energy so let's get into it 🫶

✨ NAME ✨

pipe — create an interprocess channel 💅

🌸 SYNOPSIS 🌸

#include <u.h>
#include <libc.h>

int pipe(int fd[2])

🦋 DESCRIPTION 🦋

okay so Pipe creates a buffered channel for interprocess I/O communication ✨. That's the whole vibe. Two file descriptors come back to you inside fd — literally two, no more no less, it's a duo 💅.

And here's the cute part: data written to fd[1] is available for reading from fd[0], and data written to fd[0] is available for reading from fd[1]. It goes both ways bestie, it's mutual 🌈.

Once the pipe is established, cooperating processes created by subsequent fork(2) calls may pass data through the pipe with read and write calls. group chat, but for processes, no cap 🎀

When all the data has been read from a pipe and the writer has closed the pipe or exited, read(3) will return 0 bytes — that's the "they left the chat" signal, iconic 💀.

⚠️ Writes to a pipe with no reader will generate a note sys: write on closed pipe. like yelling into a void, but the void files a complaint 😭

🧚 SOURCE 🧚

/src/lib9/pipe.c

⭐ SEE ALSO ⭐

• intro(3)
• read(3)

(iykyk, go read them, they're literally connected 💜)

🎀 DIAGNOSTICS 🎀

Sets errstr. that's it, that's the diagnostic, she's efficient 🦋

💀 BUGS 💀

okay this section is a lot, buckle up:

• If a read or a write of a pipe is interrupted, some unknown number of bytes may have been transferred. like, unknown unknown. we don't know. nobody knows. 🙈
• Pipe is a macro defined as p9pipe to avoid name conflicts with Unix's pipe system call. it's a nickname situation 👑
• Unix pipes are not guaranteed to be bidirectional. In order to ensure a bidirectional channel, p9pipe creates Unix domain sockets via the socketpair(2) instead of Unix pipes. so she's not even a pipe pipe, she's a socket in a trench coat 🧥✨
• The implementation of pipes as Unix domain sockets causes problems with some Unix implementations of /dev/fd, Unix's dup device. If a Unix domain socket is open as file descriptor 0, some implementations disallow the opening of /dev/fd/0; instead one must connect(2) to it. the audacity honestly 😤
• If this functionality is important (as it is for rc(1)), one must #undef pipe and fall back on the (possibly unidirectional) Unix pipes. so you gotta let go of the good version to get the compatible version, we've all been there 💅

🌸 that's the whole page bestie, go make some channels 🌸

💖 from PIPE(3), Library Functions Manual, footer says PIPE(3) and like, that's the version and date situation — signed off with love, xoxo 🎀🫶