fork(2)fork(2)Namefork - create a new process
Syntax
#include <sys/types.h>
#include <unistd.h>
pid = fork()
pid_t pid;
Description
The system call 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 (that is, 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 a 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 processes resource utilizations are set to 0. For fur‐
ther information, see
Return Values
Upon successful completion, 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 the global variable errno is set to indicate
the error.
Diagnostics
The system call fails and no child process are created under the fol‐
lowing conditions:
[EAGAIN] The system-imposed limit {PROC_MAX} on the total number
of processes under execution would be exceeded.
[EAGAIN] The system-imposed limit {CHILD_MAX} on the total number
of processes under execution by a single user would be
exceeded.
[ENOMEM] There is insufficient swap space for the new process.
See Alsoexecve(2), wait(2)fork(2)
