---
name: "sigblock"
section: "2"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/sigblock"
---

# sigblock(2)

block signals

## NAME

**sigblock** – block signals

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*int*\

**sigblock**(*int mask*);

*int*\

**sigmask**(*signum*);

## DESCRIPTION

This interface is made obsolete by [sigprocmask(2)](/sigprocmask/2.md).

**Sigblock**() adds the signals specified in *mask* to the set of signals currently being blocked from delivery. Signals are blocked if the corresponding bit in *mask* is a 1; the macro **sigmask**() is provided to construct the mask for a given *signum*.

It is not possible to block SIGKILL or SIGSTOP; this restriction is silently imposed by the system.

## RETURN VALUES

The previous set of masked signals is returned.

## SEE ALSO

[kill(2)](/kill/2.md), [sigaction(2)](/sigaction/2.md), [sigprocmask(2)](/sigprocmask/2.md), [sigsetmask(2)](/sigsetmask/2.md), [sigsetops(3)](/sigsetops/3.md)

## HISTORY

The **sigblock**() function call appeared in 4.2BSD and has been deprecated.