---
name: "wait4"
section: "2"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/wait4"
---

# wait4(2)

wait for process to change state, BSD style

## NAME

wait3, wait4 - wait for process to change state, BSD style

## LIBRARY

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

## SYNOPSIS

```
#include <sys/wait.h>
```

**pid\_t wait3(int \*\_Nullable** *wstatus***, int** *options***,**             **struct rusage \*\_Nullable** *rusage***);** **pid\_t wait4(pid\_t** *pid***, int \*\_Nullable** *wstatus***, int** *options***,**             **struct rusage \*\_Nullable** *rusage***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**wait3**():

```
    Since glibc 2.26:
        _DEFAULT_SOURCE
            || (_XOPEN_SOURCE >= 500 &&
                ! (_POSIX_C_SOURCE >= 200112L
                   || _XOPEN_SOURCE >= 600))
    From glibc 2.19 to glibc 2.25:
        _DEFAULT_SOURCE || _XOPEN_SOURCE >= 500
    glibc 2.19 and earlier:
        _BSD_SOURCE || _XOPEN_SOURCE >= 500
```

**wait4**():

```
    Since glibc 2.19:
        _DEFAULT_SOURCE
    glibc 2.19 and earlier:
        _BSD_SOURCE
```

## DESCRIPTION

These functions are nonstandard; in new programs, the use of [**waitpid**(2)](/waitpid/2.md) or [**waitid**(2)](/waitid/2.md) is preferable.

The **wait3**() and **wait4**() system calls are similar to [**waitpid**(2)](/waitpid/2.md), but additionally return resource usage information about the child in the structure pointed to by *rusage*.

Other than the use of the *rusage* argument, the following **wait3**() call:

```
wait3(wstatus, options, rusage);
```

is equivalent to:

```
waitpid(-1, wstatus, options);
```

Similarly, the following **wait4**() call:

```
wait4(pid, wstatus, options, rusage);
```

is equivalent to:

```
waitpid(pid, wstatus, options);
```

In other words, **wait3**() waits of any child, while **wait4**() can be used to select a specific child, or children, on which to wait. See [**wait**(2)](/wait/2.md) for further details.

If *rusage* is not NULL, the *struct rusage* to which it points will be filled with accounting information about the child. See [**getrusage**(2)](/getrusage/2.md) for details.

## RETURN VALUE

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

## ERRORS

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

## STANDARDS

None.

## HISTORY

4\.3BSD.

SUSv1 included a specification of **wait3**(); SUSv2 included **wait3**(), but marked it LEGACY; SUSv3 removed it.

Including *\<sys/time.h\>* is not required these days, but increases portability. (Indeed, *\<sys/resource.h\>* defines the *rusage* structure with fields of type *struct timeval* defined in *\<sys/time.h\>*.)

### C library/kernel differences

On Linux, **wait3**() is a library function implemented on top of the **wait4**() system call.

## SEE ALSO

[**fork**(2)](/fork/2.md), [**getrusage**(2)](/getrusage/2.md), [**sigaction**(2)](/sigaction/2.md), [**signal**(2)](/signal/2.md), [**wait**(2)](/wait/2.md), [**signal**(7)](/signal/7.md)