---
name: "sigset"
section: "2"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/sighold"
---

# sigset(2)

legacy interface for signal management

Part of [sighold(2)](/sighold/2.md).

## NAME

**sighold**, **sigignore**, **sigpause**, **sigrelse**, **sigset** – legacy interface for signal management

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<signal.h\>**

*int*\

**sighold**(*int sig*);

*int*\

**sigignore**(*int sig*);

*int*\

**xsi\_sigpause**(*int sigmask*);

*int*\

**sigrelse**(*int sig*);

*void* *(\*)(int)*\

**sigset**(*int*, *void (\*disp)(int)*);

*int*\

**sigpause**(*int sigmask*);

## DESCRIPTION

**This** **interface** **is** **made** **obsolete** **by** [sigsuspend(2)](/sigsuspend/2.md) **and** [sigaction(2)](/sigaction/2.md).

The **sigset**() function modifies signal dispositions. The *sig* argument specifies the signal, which may be any signal except SIGKILL and SIGSTOP. The *disp* argument specifies the signal's disposition, which may be SIG\_DFL, SIG\_IGN, or the address of a signal handler. If **sigset**() is used, and *disp* is the address of a signal handler, the system adds *sig* to the signal mask of the calling process before executing the signal handler; when the signal handler returns, the system restores the signal mask of the calling process to its state prior to the delivery of the signal. In addition, if **sigset**() is used, and *disp* is equal to SIG\_HOLD, *sig* is added to the signal mask of the calling process and *sig*, *'s* disposition remains unchanged. If **sigset**() is used, and *disp* is not equal to SIG\_HOLD, *sig* is removed from the signal mask of the calling process.

The **sighold**() function adds *sig* to the signal mask of the calling process.

The **sigrelse**() function removes *sig* from the signal mask of the calling process.

The **sigignore**() function sets the disposition of *sig* to SIG\_IGN.

The **xsi\_sigpause**() function removes *sig* from the signal mask of the calling process and suspend the calling process until a signal is received. The **xsi\_sigpause**() function restores the signal mask of the process to its original state before returning.

The **sigpause**() function assigns *sigmask* to the set of masked signals and then waits for a signal to arrive; on return the set of masked signals is restored. The *sigmask* argument is usually 0 to indicate that no signals are to be blocked.

## RETURN VALUES

The **sigpause**() and **xsi\_sigpause**() functions always terminate by being interrupted, returning -1 with *errno* set to EINTR.

Upon successful completion, **sigset**() returns SIG\_HOLD if the signal had been blocked and the signal's previous disposition if it had not been blocked. Otherwise, SIG\_ERR is returned and *errno* set to indicate the error.

For all other functions, upon successful completion, 0 is returned. Otherwise, -1 is returned and *errno* is set to indicate the error:

- \[EINVAL\]

  The *sig* argument is not a valid signal number.

- \[EINVAL\]

  For **sigset**() and **sigignore**() functions, an attempt was made to catch or ignore SIGKILL or SIGSTOP.

## SEE ALSO

[kill(2)](/kill/2.md), [sigaction(2)](/sigaction/2.md), [sigblock(2)](/sigblock/2.md), [sigprocmask(2)](/sigprocmask/2.md), [sigsuspend(2)](/sigsuspend/2.md), [sigvec(2)](/sigvec/2.md)

## STANDARDS

The **sigpause**() function is implemented for compatibility with historic 4.3BSD applications. An incompatible interface by the same name, which used a single signal number rather than a mask, was present in AT&T System V UNIX, and was copied from there into the **X/Open** **System** **Interfaces** (XSI) option of IEEE Std 1003.1-2001 (“POSIX.1”). FreeBSD implements it under the name **xsi\_sigpause**(). The **sighold**(), **sigignore**(), **sigrelse**() and **sigset**() functions are implemented for compatibility with **System** **V** and **XSI** interfaces.

## HISTORY

The **sigpause**() function appeared in 4.2BSD and has been deprecated. All other functions appeared in FreeBSD 8.1 and were deprecated before being implemented.