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.\" 34.Dd July 25, 2015 35.Dt SYSTEM 3 36.Os 37.Sh NAME 38.Nm system 39.Nd pass a command to the shell 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In stdlib.h 44.Ft int 45.Fn system "const char *string" 46.Sh DESCRIPTION 47The 48.Fn system 49function 50hands the argument 51.Fa string 52to the command interpreter 53.Xr sh 1 . 54The calling process waits for the shell 55to finish executing the command, 56ignoring 57.Dv SIGINT 58and 59.Dv SIGQUIT , 60and blocking 61.Dv SIGCHLD . 62.Pp 63If 64.Fa string 65is a 66.Dv NULL 67pointer, 68.Fn system 69will return non-zero if the command interpreter 70.Xr sh 1 71is available, and zero if it is not. 72.Sh RETURN VALUES 73The 74.Fn system 75function 76returns the exit status of the shell as returned by 77.Xr waitpid 2 , 78or \-1 if an error occurred when invoking 79.Xr fork 2 80or 81.Xr waitpid 2 . 82A return value of 127 means the execution of the shell 83failed. 84.Sh SEE ALSO 85.Xr sh 1 , 86.Xr execve 2 , 87.Xr fork 2 , 88.Xr waitpid 2 , 89.Xr popen 3 , 90.Xr posix_spawn 3 91.Sh STANDARDS 92The 93.Fn system 94function 95conforms to 96.St -isoC 97and is expected to be 98.St -p1003.2 99compatible. 100.Sh SECURITY CONSIDERATIONS 101The 102.Fn system 103function is easily misused in a manner that enables a malicious 104user to run arbitrary command, 105because all meta-characters supported by 106.Xr sh 1 107would be honored. 108User supplied parameters should always be carefully santized 109before they appear in 110.Fa string . 111