---
name: "bsd_signal"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/bsd_signal"
---

# bsd\_signal(3)

signal handling with BSD semantics

## NAME

bsd\_signal - signal handling with BSD semantics

## LIBRARY

Standard C library (*libc*, *-lc*)

## 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 (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**bsd\_signal**():

```
    Since glibc 2.26:
        _XOPEN_SOURCE >= 500
            && ! (_POSIX_C_SOURCE >= 200809L)
    glibc 2.25 and earlier:
        _XOPEN_SOURCE
```

## DESCRIPTION

The **bsd\_signal**() function takes the same arguments, and performs the same task, as [**signal**(2)](/signal/2.md).

The difference between the two is that **bsd\_signal**() is guaranteed to provide reliable signal semantics, that is: a) the disposition of the signal is not reset to the default when the handler is invoked; b) delivery of further instances of the signal is blocked while the signal handler is executing; and c) if the handler interrupts a blocking system call, then the system call is automatically restarted. A portable application cannot rely on [**signal**(2)](/signal/2.md) to provide these guarantees.

## RETURN VALUE

The **bsd\_signal**() function returns the previous value of the signal handler, or **SIG\_ERR** on error.

## ERRORS

As for [**signal**(2)](/signal/2.md).

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **bsd\_signal**() | Thread safety | MT-Safe |

## VERSIONS

Use of **bsd\_signal**() should be avoided; use [**sigaction**(2)](/sigaction/2.md) instead.

On modern Linux systems, **bsd\_signal**() and [**signal**(2)](/signal/2.md) are equivalent. But on older systems, [**signal**(2)](/signal/2.md) provided unreliable signal semantics; see [**signal**(2)](/signal/2.md) for details.

The use of *sighandler\_t* is a GNU extension; this type is defined only if the **\_GNU\_SOURCE** feature test macro is defined.

## STANDARDS

None.

## HISTORY

4\.2BSD, POSIX.1-2001. Removed in POSIX.1-2008, recommending the use of [**sigaction**(2)](/sigaction/2.md) instead.

## SEE ALSO

[**sigaction**(2)](/sigaction/2.md), [**signal**(2)](/signal/2.md), [**sysv\_signal**(3)](/sysv_signal/3.md), [**signal**(7)](/signal/7.md)