---
name: "setpgrp"
section: "2"
platform: "macos"
package: "xnu"
version: "12377.121.6"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/setpgid/2"
---

# setpgrp(2)

set process group

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

## NAME

**setpgid**, **setpgrp** – set process group

## SYNOPSIS

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

*int*\

**setpgid**(*pid\_t pid*, *pid\_t pgid*);

*pid\_t*\

**setpgrp**(*void*);

## DESCRIPTION

**setpgid**() sets the process group of the specified process *pid* to the specified *pgid*. If *pid* is zero, then the call applies to the current process.

If the invoker is not the super-user, then the affected process must have the same effective user-id as the invoker or be a descendant of the invoking process.

## RETURN VALUES

**setpgid**() returns 0 when the operation was successful. If the request failed, -1 is returned and the global variable *errno* indicates the reason.

## ERRORS

**setpgid**() will fail and the process group will not be altered if:

- \[EACCES\]

  The value of the *pid* argument matches the process ID of a child process of the calling process,  and the child process has successfully executed one of the exec functions.

- \[EINVAL\]

  The value of the *pgid* argument is less than 0 or is not a value supported by the implementation.

- \[EPERM\]

  The process indicated by the *pid* argument is a session leader.

- \[EPERM\]

  The effective user ID of the requested process is different from that of the caller and the process is not a descendant of the calling process.

- \[EPERM\]

  The value of the *pgid*, *argument* is valid, but does not match the process ID of the process indicated by the *pid* argument and there is no process with a process group ID that matches the value of the *pgid* argument in the same session as the calling process.

- \[ESRCH\]

  The value of the  *pid* argument does not match the process ID of the calling process or of a  child process of the calling process.

## LEGACY SYNOPSIS

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

*int*\
 **setpgrp**(*pid\_t pid*, *pid\_t pgid*);

The legacy **setpgrp**() function is a clone of the **setpgid**() function, retained for calling convention compatibility with historical versions of BSD.

## COMPATIBILITY

Use of the legacy version of the **setpgrp**() call will cause compiler diagnostics. Use **setpgid**() instead.

Use of private (and conflicting) prototypes for **setpgrp**() will cause compiler diagnostics. Delete the private prototypes and include ⟨unistd.h⟩.

## SEE ALSO

[getpgrp(2)](/getpgrp/2.md), [compat(5)](/compat/5.md)

## STANDARDS

The **setpgid**() function conforms to  IEEE Std 1003.1-1988 (“POSIX.1”).