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

# sigwaitinfo(2)

wait for queued signals (REALTIME)

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

## NAME

**sigtimedwait**, **sigwaitinfo** – wait for queued signals (REALTIME)

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*int*\

**sigtimedwait**(*const sigset\_t \*restrict set*, *siginfo\_t \*restrict info*, *const struct timespec \*restrict timeout*);

*int*\

**sigwaitinfo**(*const sigset\_t \* restrict set*, *siginfo\_t \* restrict info*);

## DESCRIPTION

The **sigtimedwait**() system call is equivalent to **sigwaitinfo**() except that if none of the signals specified by *set* are pending, **sigtimedwait**() waits for the time interval specified in the *timespec* structure referenced by *timeout*. If the *timespec* structure pointed to by *timeout* is zero-valued and if none of the signals specified by *set* are pending, then **sigtimedwait**() returns immediately with an error. If *timeout* is the NULL pointer, **sigtimedwait**() blocks indefinitely. CLOCK\_MONOTONIC clock is used to measure the time interval specified by the *timeout* argument.

The **sigwaitinfo**() system call selects the pending signal from the set specified by *set*. Should any of multiple pending signals in the range SIGRTMIN to SIGRTMAX be selected, it shall be the lowest numbered one. The selection order between realtime and non-realtime signals, or between multiple pending non-realtime signals, is unspecified. If no signal in *set* is pending at the time of the call, the calling thread is suspended until one or more signals in *set* become pending or until it is interrupted by an unblocked, caught signal.

The **sigwaitinfo**() system call is equivalent to the **sigwait**() system call if the *info* argument is NULL. If the *info* argument is non-NULL, the **sigwaitinfo**() function is equivalent to **sigwait**(), except that the selected signal number shall be stored in the *si\_signo* member, and the cause of the signal shall be stored in the *si\_code* member. Besides this, the **sigwaitinfo**() and **sigtimedwait**() system calls may return EINTR if interrupted by signal, which is not allowed for the **sigwait**() function.

If any value is queued to the selected signal, the first such queued value is dequeued and, if the info argument is non-NULL, the value is stored in the *si\_value* member of *info*. The system resource used to queue the signal is released and returned to the system for other use. If no value is queued, the content of the *si\_value* member is zero-valued. If no further signals are queued for the selected signal, the pending indication for that signal is reset.

## RETURN VALUES

Upon successful completion (that is, one of the signals specified by *set* is pending or is generated) **sigwaitinfo**() and **sigtimedwait**() return the selected signal number. Otherwise, the functions return a value of -1 and set the global variable *errno* to indicate the error.

## ERRORS

The **sigtimedwait**() system call will fail if:

- \[EAGAIN\]

  No signal specified by set was generated within the specified timeout period.

The **sigtimedwait**() and **sigwaitinfo**() system calls fail if:

- \[EINTR\]

  The wait was interrupted by an unblocked, caught signal.

The **sigtimedwait**() system call may also fail if:

- \[EINVAL\]

  The *timeout* argument specified a *tv\_nsec* value less than zero or greater than or equal to 1000 million. Kernel only checks for this error if no signal is pending in set and it is necessary to wait.

## SEE ALSO

[sigaction(2)](/sigaction/2.md), [sigpending(2)](/sigpending/2.md), [sigqueue(2)](/sigqueue/2.md), [sigsuspend(2)](/sigsuspend/2.md), [sigwait(2)](/sigwait/2.md), [pause(3)](/pause/3.md), [pthread\_sigmask(3)](/pthread_sigmask/3.md), [siginfo(3)](/siginfo/3.md)

## STANDARDS

The **sigtimedwait**() and **sigwaitinfo**() system calls conform to ISO/IEC 9945-1:1996 (“POSIX.1”). POSIX leaves the behavior of **sigtimedwait**() with a NULL *timeout* pointer unspecified.