---
name: "sigsetops"
section: "3"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/sigsetops"
---

# sigsetops(3)

manipulate signal sets

## NAME

**sigaddset**, **sigdelset**, **sigemptyset**, **sigfillset**, **sigismember** – manipulate signal sets

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*int*\

**sigaddset**(*sigset\_t \*set*, *int signo*);

*int*\

**sigdelset**(*sigset\_t \*set*, *int signo*);

*int*\

**sigemptyset**(*sigset\_t \*set*);

*int*\

**sigfillset**(*sigset\_t \*set*);

*int*\

**sigismember**(*const sigset\_t \*set*, *int signo*);

## DESCRIPTION

These functions manipulate signal sets, stored in a *sigset\_t*. Either **sigemptyset**() or **sigfillset**() must be called for every object of type *sigset\_t* before any other use of the object.

The **sigemptyset**() function initializes a signal set to be empty.

The **sigfillset**() function initializes a signal set to contain all signals.

The **sigaddset**() function adds the specified signal *signo* to the signal set.

The **sigdelset**() function deletes the specified signal *signo* from the signal set.

The **sigismember**() function returns whether a specified signal *signo* is contained in the signal set.

These functions are provided as macros in the include file \<signal.h\>. Actual functions are available if their names are undefined (with #undef *name*).

## RETURN VALUES

The **sigismember**() function returns 1 if the signal is a member of the set, 0 otherwise. The other functions return 0.

## ERRORS

Currently, no errors are detected.

## SEE ALSO

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

## STANDARDS

These functions are defined by IEEE Std 1003.1-1988 (“POSIX.1”).