.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)system.3	8.1 (Berkeley) 6/4/93
.\" %FreeBSD: src/lib/libc/stdlib/system.3,v 1.6.2.4 2001/12/14 18:33:58 ru Exp %
.\"
.\" $FreeBSD$
.Dd June 4, 1993
.Dt SYSTEM 3
.Os
.Sh 名称
.Nm system
.Nd コマンドをシェルに渡す
.Sh ライブラリ
.Lb libc
.Sh 書式
.In stdlib.h
.Ft int
.Fn system "const char *string"
.Sh 解説
.Fn system
関数は、引数
.Fa string
をコマンドインタプリタ
.Xr sh 1
に渡します。
呼び出し元プロセスは、シェルがそのコマンドの実行を
完了するまで待ち、
.Dv SIGINT
および
.Dv SIGQUIT
を無視し、
.Dv SIGCHLD
をブロックします。
.Pp
.Fa string
が
.Dv NULL
ポインタの場合、
.Fn system
はコマンドインタプリタ
.Xr sh 1
が利用できる場合は 0 以外の値を返し、
利用できない場合は 0 を返します。
.Pp
.Xr fork 2
もしくは
.Xr waitpid 2
を呼び出したときにエラーが発生した場合、
.Fn system
関数は、
.Xr waitpid 2
で返されるシェルの終了状態、
あるいは
\-1 を返します。
戻り値 127 は、シェルの実行が
失敗したことを意味します。
.Sh 関連項目
.Xr sh 1 ,
.Xr execve 2 ,
.Xr wait 2 ,
.Xr fork 2 ,
.Xr waitpid 2 ,
.Xr popen 3
.Sh 規格
.Fn system
関数は、
.St -isoC
に適合しており、
.St -p1003.2
と互換性があると思われます。