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.Dd July 25, 2015 33.Dt SYSTEM 3 34.Os 35.Sh NAME 36.Nm system 37.Nd pass a command to the shell 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In stdlib.h 42.Ft int 43.Fn system "const char *string" 44.Sh DESCRIPTION 45The 46.Fn system 47function 48hands the argument 49.Fa string 50to the command interpreter 51.Xr sh 1 . 52The calling process waits for the shell 53to finish executing the command, 54ignoring 55.Dv SIGINT 56and 57.Dv SIGQUIT , 58and blocking 59.Dv SIGCHLD . 60.Pp 61If 62.Fa string 63is a 64.Dv NULL 65pointer, 66.Fn system 67will return non-zero if the command interpreter 68.Xr sh 1 69is available, and zero if it is not. 70.Sh RETURN VALUES 71The 72.Fn system 73function 74returns the exit status of the shell as returned by 75.Xr waitpid 2 , 76or \-1 if an error occurred when invoking 77.Xr fork 2 78or 79.Xr waitpid 2 . 80A return value of 127 means the execution of the shell 81failed. 82.Sh SEE ALSO 83.Xr sh 1 , 84.Xr execve 2 , 85.Xr fork 2 , 86.Xr waitpid 2 , 87.Xr popen 3 , 88.Xr posix_spawn 3 89.Sh STANDARDS 90The 91.Fn system 92function 93conforms to 94.St -isoC 95and is expected to be 96.St -p1003.2 97compatible. 98.Sh SECURITY CONSIDERATIONS 99The 100.Fn system 101function is easily misused in a manner that enables a malicious 102user to run arbitrary command, 103because all meta-characters supported by 104.Xr sh 1 105would be honored. 106User supplied parameters should always be carefully santized 107before they appear in 108.Fa string . 109