HP-UX Reference (11i v2 04/09) - 2 System Calls (vol 5)

fork(2) fork(2)

If a parent and child process both have a ﬁle opened and the parent or child closes the ﬁle, the ﬁle is still

open for the other process.

RETURN VALUE

Upon successful completion,

fork() returns a value of

0 to the child process and returns the process ID

of the child process to the parent process. Otherwise, a value of −1 is returned to the parent process, no

child process is created, and

errno is set to indicate the error.

The parent and child processes resume execution immediately after the

fork() call; they are dis-

tinguished by the value returned by

fork.

ERRORS

fork() fails, errno is set to one of the following values.

[EAGAIN] The system-imposed limit on the total number of processes under execution would

be exceeded.

[EAGAIN] The system-imposed limit on the total number of processes under execution by a

single user would be exceeded.

[ENOMEM] There is insufﬁcient swap space and/or physical memory available in which to

create the new process.

WARNINGS

Standard I/O streams (see stdio (3S)) are duplicated in the child. Therefore, if

fork is called after a

buffered I/O operation without ﬁrst closing or ﬂushing the associated standard I/O stream (see fclose (3S)),

the buffered input or output might be duplicated.

DEPENDENCIES

HP Process Resource Manager

If the optional HP Process Resource Manager (PRM) software is installed and conﬁgured, the child pro-

cess inherits the parent’s process resource group ID. See prmconﬁg(1) for a description of how to

conﬁgure HP PRM, and prmconf(4) for the deﬁnition of process resource group.

AUTHOR

fork() was developed by AT&T, the University of California, Berkeley, and HP.