---
name: "vfork"
section: "2freebsd"
platform: "linux"
package: "freebsd-manpages"
version: "12.2-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/vfork/2freebsd"
---

# vfork(2freebsd)

create a new process without copying the address space

## NAME

**vfork** – create a new process without copying the address space

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*pid\_t*\

**vfork**(*void*);

## DESCRIPTION

Since this function is hard to use correctly from application software, it is recommended to use [posix\_spawn(3)](/posix_spawn/3.md) or [fork(2)](/fork/2.md) instead.

The **vfork**() system call can be used to create new processes without fully copying the address space of the old process, which is inefficient in a paged environment. It is useful when the purpose of [fork(2)](/fork/2.md) would have been to create a new system context for an [execve(2)](/execve/2.md). The **vfork**() system call differs from [fork(2)](/fork/2.md) in that the child borrows the parent process's address space and the calling thread's stack until a call to [execve(2)](/execve/2.md) or an exit (either by a call to [\_exit(2)](/_exit/2.md) or abnormally). The calling thread is suspended while the child is using its resources. Other threads continue to run.

The **vfork**() system call returns 0 in the child's context and (later) the pid of the child in the parent's context.

Many problems can occur when replacing [fork(2)](/fork/2.md) with **vfork**(). For example, it does not work to return while running in the child's context from the procedure that called **vfork**() since the eventual return from **vfork**() would then return to a no longer existent stack frame. Also, changing process state which is partially implemented in user space such as signal handlers with [libthr(3)](/libthr/3.md) will corrupt the parent's state.

Be careful, also, to call [\_exit(2)](/_exit/2.md) rather than [exit(3)](/exit/3.md) if you cannot [execve(2)](/execve/2.md), since [exit(3)](/exit/3.md) will flush and close standard I/O channels, and thereby mess up the parent processes standard I/O data structures. (Even with [fork(2)](/fork/2.md) it is wrong to call [exit(3)](/exit/3.md) since buffered data would then be flushed twice.)

## RETURN VALUES

Same as for [fork(2)](/fork/2.md).

## SEE ALSO

[\_exit(2)](/_exit/2.md), [execve(2)](/execve/2.md), [fork(2)](/fork/2.md), [rfork(2)](/rfork/2.md), [sigaction(2)](/sigaction/2.md), [wait(2)](/wait/2.md), [exit(3)](/exit/3.md), [posix\_spawn(3)](/posix_spawn/3.md)

## HISTORY

The **vfork**() system call appeared in 3BSD.

## BUGS

To avoid a possible deadlock situation, processes that are children in the middle of a **vfork**() are never sent SIGTTOU or SIGTTIN signals; rather, output or [ioctl(2)](/ioctl/2.md) calls are allowed and input attempts result in an end-of-file indication.