1.\" $NetBSD: system.3,v 1.17 2008/08/27 06:45:02 christos Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" the American National Standards Committee X3, on Information 8.\" Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)system.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd August 2, 2007 37.Dt SYSTEM 3 38.Os 39.Sh NAME 40.Nm system 41.Nd pass a command to the shell 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In stdlib.h 46.Ft int 47.Fn system "const char *string" 48.Sh DESCRIPTION 49The 50.Fn system 51function 52hands the argument 53.Fa string 54to the command interpreter 55.Xr sh 1 . 56The calling process waits for the shell to finish executing the command, 57ignoring 58.Dv SIGINT 59and 60.Dv SIGQUIT , 61and blocking 62.Dv SIGCHLD . 63.Pp 64If 65.Fa string 66is a 67.Dv NULL 68pointer, 69.Fn system 70will return non-zero, if the command interpreter is available, or zero if none 71is available. 72Otherwise, 73.Fn system 74returns the termination status of the shell in the format specified by 75.Xr waitpid 2 . 76.Sh RETURN VALUES 77If a child process cannot be created, or the termination status of 78the shell cannot be obtained, 79.Fn system 80returns -1 and sets 81.Va errno 82to indicate the error. 83If execution of the shell fails, 84.Fn system 85returns the termination status for a program that terminates with a call of 86.Fn exit 127 . 87.Sh SEE ALSO 88.Xr sh 1 , 89.Xr execve 2 , 90.Xr waitpid 2 , 91.Xr popen 3 , 92.Xr shquote 3 93.Sh STANDARDS 94The 95.Fn system 96function 97conforms to 98.St -ansiC 99and 100.St -p1003.2-92 . 101.Sh CAVEATS 102Never supply the 103.Fn system 104function with a command containing any part of an unsanitized user-supplied 105string. 106Shell meta-characters present will be honored by the 107.Xr sh 1 108command interpreter. 109