BINDAT(2)

💅 BINDAT(2) — the bind but make it directory-relative page

okay so this is a system calls manual page, from section 2, and it's giving "we made bind(2) but with a file descriptor glow-up". Let's get into it bestie 🎀

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✨ NAME ✨

bindat — assign a local protocol address to a socket

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📚 LIBRARY 📚

Standard C Library (libc, -lc)

like, that's the one you already link against, no cap.

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🌸 SYNOPSIS 🌸

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

#include <fcntl.h>

int
bindat(int fd, int s, const struct sockaddr *addr, socklen_t addrlen);

so the four things you're handing over are fd, s, addr, and addrlen. and yes you need all those headers, don't fight it 💖

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🦋 DESCRIPTION 🦋

The bindat() system call assigns the local protocol address to a socket. periodt.

When you pass the special value AT_FDCWD in the fd parameter, the behavior is identical to a call to bind(2). like, literally the same thing. no notes.

Otherwise, bindat() works like the bind(2) system call with exactly two exceptions, and bestie these are the whole personality:

1. It is limited to sockets in the PF_LOCAL domain. 👑 only local-domain girlies allowed.
2. If the file path stored in the sun_path field of the sockaddr_un structure is a relative path, it is located relative to the directory associated with the file descriptor fd.

so yeah, that's the whole bit — relative paths get resolved against fd instead of wherever your process happens to be chillin. iykyk 💅

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⭐ RETURN VALUES ⭐

• The bindat() function returns the value 0 if successful ✨
• otherwise the value -1 is returned and the global variable errno is set to indicate the error 😭

zero means slay, negative one means check errno. that's it that's the vibe check.

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💀 ERRORS 💀

The bindat() system call may fail with the same errors as the bind(2) system call, or with the following errors:

• [EBADF] — The sun_path field does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor. 🙈
• [ENOTDIR] — The sun_path field is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

ngl both of these are the "you gave me a relative path AND a bad fd" combo special. the path being relative is fine, the fd being trash is not. 🫶

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🔥 SEE ALSO 🔥

• bind(2)
• connectat(2)
• socket(2)
• unix(4)

go read the friends, they're all iconic in their own way 💜

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🎀 AUTHORS 🎀

The bindat was developed by Pawel Jakub Dawidek <pawel@dawidek.net> under sponsorship from the FreeBSD Foundation. 🫶 giving patron-energy, honestly.

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and that's the whole page bestie!! this one came from Debian, dated February 13, 2013, and it lives in BINDAT(2) — section 2, system calls manual. mwah 💋 go bind something responsibly ✨