1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)system.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd July 25, 2015 36.Dt SYSTEM 3 37.Os 38.Sh NAME 39.Nm system 40.Nd pass a command to the shell 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In stdlib.h 45.Ft int 46.Fn system "const char *string" 47.Sh DESCRIPTION 48The 49.Fn system 50function 51hands the argument 52.Fa string 53to the command interpreter 54.Xr sh 1 . 55The calling process waits for the shell 56to 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 71.Xr sh 1 72is available, and zero if it is not. 73.Sh RETURN VALUES 74The 75.Fn system 76function 77returns the exit status of the shell as returned by 78.Xr waitpid 2 , 79or \-1 if an error occurred when invoking 80.Xr fork 2 81or 82.Xr waitpid 2 . 83A return value of 127 means the execution of the shell 84failed. 85.Sh SEE ALSO 86.Xr sh 1 , 87.Xr execve 2 , 88.Xr fork 2 , 89.Xr waitpid 2 , 90.Xr popen 3 , 91.Xr posix_spawn 3 92.Sh STANDARDS 93The 94.Fn system 95function 96conforms to 97.St -isoC 98and is expected to be 99.St -p1003.2 100compatible. 101.Sh SECURITY CONSIDERATIONS 102The 103.Fn system 104function is easily misused in a manner that enables a malicious 105user to run arbitrary command, 106because all meta-characters supported by 107.Xr sh 1 108would be honored. 109User supplied parameters should always be carefully santized 110before they appear in 111.Fa string. 112