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fork(2) [ultrix man page]

fork(2) 							System Calls Manual							   fork(2)

Name
       fork - 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:

       o    The child process has a unique process ID.

       o    The child process has a different parent process ID (that is, the process ID of the parent process).

       o    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.

       o    The child processes resource utilizations are set to 0.  For further 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 following 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 Also
       execve(2), wait(2)

																	   fork(2)

Check Out this Related Man Page

FORK(2) 							System Calls Manual							   FORK(2)

NAME
fork - create a new process SYNOPSIS
pid = fork() int pid; 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 processes resource utilizations are set to 0; see setrlimit(2). 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 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. [EAGAIN] The system-imposed limit MAXUPRC (<sys/param.h>) 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 ALSO
execve(2), wait(2) 3rd Berkeley Distribution May 22, 1986 FORK(2)
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