bsd_signal(3)

💖 bsd_signal — bestie, it's signal handling but with BSD flavor 💖

okay so you know signal(2)? this is that, but from the ✨BSD✨ side of the family. it lives in the Standard C library (libc, link that bad boy with -lc). let's get into it 🌸

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✨ SYNOPSIS ✨

#include <signal.h>

typedef typeof(void (int))  *sighandler_t;

sighandler_t bsd_signal(int signum, sighandler_t handler);

🎀 Feature Test Macro Requirements for glibc (peep feature_test_macros(7) for the tea)

• bsd_signal():
  • Since glibc 2.26:

_XOPEN_SOURCE >= 500
    && ! (_POSIX_C_SOURCE >= 200809L)

• glibc 2.25 and earlier:

_XOPEN_SOURCE

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🌈 DESCRIPTION 🌈

so bsd_signal() takes the exact same arguments and does the exact same job as signal(2). same energy, same task, no cap 🫶

the difference?? the whole difference, and it's lowkey the important part: bsd_signal() is guaranteed to give you reliable signal semantics. which means:

1. the disposition of the signal is not reset to the default when the handler gets invoked 🙅
2. delivery of further instances of the signal is blocked while the signal handler is executing 🔒
3. if the handler interrupts a blocking system call, then that system call is automatically restarted 🔁

meanwhile a portable application literally cannot rely on signal(2) to give you any of those guarantees. so like… note that, bestie 📝

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💫 RETURN VALUE 💫

bsd_signal() hands you back the previous value of the signal handler, or SIG_ERR if something went wrong. SIG_ERR is giving 💀, the previous value is giving 👑

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🚨 ERRORS 🚨

same as signal(2), fr fr. go read that one.

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👑 ATTRIBUTES 👑

for an explanation of the terms used in this section, see attributes(7). since we can't do tables here (the vibes forbid it), here's the tea in list form:

• bsd_signal() — Thread safety: MT-Safe 🧵✨ (yes bestie, it's thread-safe, we love to see it)

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💅 VERSIONS 💅

okay real talk:

Use of bsd_signal() should be avoided; use sigaction(2) instead.

not me being dramatic, that's literally what it says. use sigaction(2). periodt.

on modern Linux systems, bsd_signal() and signal(2) are equivalent. but on older systems, signal(2) provided unreliable signal semantics — check signal(2) for the details if you're curious 👀

and psa: the use of sighandler_t is a GNU extension 🐂 — this type is defined only if the _GNU_SOURCE feature test macro is defined. so if it's not showing up, that's why, and now you know 🎀

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📜 STANDARDS 📜

None. that's it. that's the whole section. iconic behaviour honestly 💀

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🦋 HISTORY 🦋

• 4.2BSD, POSIX.1-2001.
• Removed in POSIX.1-2008, recommending the use of sigaction(2) instead. so it got un-invited from the party 🥲

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🌟 SEE ALSO 🌟

• sigaction(2)
• signal(2)
• sysv_signal(3)
• signal(7)

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k that's the whole page bestie, go handle your signals responsibly 🫶✨

this was Linux man-pages 6.20, dated 2026-02-08 — mwah, love that for us 💜