NAME
fork - create a new process
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
pid_t fork(void)
DESCRIPTION
Fork causes creation of a new process. The new process
(child process) is an exact copy of the calling process
except for the following:
The child process has a unique process ID.
The child process has a different parent process ID
(i.e., the process ID of the parent process).
The child process has its own copy of the parent's
descriptors. These descriptors reference the same
underlying objects, so that, for instance, file
pointers in file objects are shared between the child
and the parent, so that an lseek(2) on a descriptor in
the child process can affect a subsequent read or write
by the parent. This descriptor copying is also used by
the shell to establish standard input and output for
newly created processes as well as to set up pipes.
The child starts with no pending signals and an inac-
tive alarm timer.
RETURN VALUE
Upon successful completion, fork returns a value of 0 to the
child process and returns the process ID of the child pro-
cess to the parent process. Otherwise, a value of -1 is
returned to the parent process, no child process is created,
and the global variable errno is set to indicate the error.
ERRORS
Fork will fail and no child process will be created if one
or more of the following are true:
[EAGAIN] The system-imposed limit on the total number
of processes under execution would be
exceeded. This limit is configuration-
dependent. (The kernel variable NR_PROCS in
<minix/config.h> (Minix), or <minix/const.h>
(Minix-vmd).)
[ENOMEM] There is insufficient (virtual) memory for
the new process.
SEE ALSO
execve(2), wait(2).