75 lines
2.1 KiB
Groff
75 lines
2.1 KiB
Groff
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.\" Copyright (c) 1980 Regents of the University of California.
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.\" All rights reserved. The Berkeley software License Agreement
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.\" specifies the terms and conditions for redistribution.
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.\"
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.\" @(#)fork.2 6.4 (Berkeley) 5/22/86
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.\"
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.TH FORK 2 "May 22, 1986"
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.UC
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.SH NAME
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fork \- create a new process
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.SH SYNOPSIS
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.nf
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.ft B
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#include <sys/types.h>
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#include <unistd.h>
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pid_t fork(void)
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.ft R
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.fi
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.SH DESCRIPTION
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.de SP
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.if t .sp 0.4
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.if n .sp
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..
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.B Fork
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causes creation of a new process.
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The new process (child process) is an exact copy of the
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calling process except for the following:
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.RS
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.SP
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The child process has a unique process ID.
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.SP
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The child process has a different parent process ID (i.e.,
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the process ID of the parent process).
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.SP
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The child process has its own copy of the parent's descriptors.
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These descriptors reference the same underlying objects, so that,
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for instance, file pointers in file objects are shared between
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the child and the parent, so that an
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.BR lseek (2)
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on a descriptor in the child process can affect a subsequent
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.B read
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or
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.B write
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by the parent.
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This descriptor copying is also used by the shell to
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establish standard input and output for newly created processes
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as well as to set up pipes.
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.SP
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The child starts with no pending signals and an inactive alarm timer.
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.RE
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.SH "RETURN VALUE
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Upon successful completion, \fBfork\fP returns a value
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of 0 to the child process and returns the process ID of the child
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process to the parent process. Otherwise, a value of \-1 is returned
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to the parent process, no child process is created, and the global
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variable \fBerrno\fP is set to indicate the error.
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.SH ERRORS
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.B Fork
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will fail and no child process will be created if one or more of the
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following are true:
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.TP 15
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[EAGAIN]
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The system-imposed limit on the total
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number of processes under execution would be exceeded.
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This limit is configuration-dependent.
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(The kernel variable NR_PROCS in <minix/config.h> (Minix), or
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<minix/const.h> (Minix-vmd).)
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.TP 15
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[ENOMEM]
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There is insufficient (virtual) memory for the new process.
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.SH "SEE ALSO"
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.BR execve (2),
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.BR wait (2).
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