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Our manual page currently states that system() will return 127 if it fails to execute the shell. The actual return value is, to quote POSIX, “as if the command language interpreter had terminated using exit(127) or _exit(127)”. MFC after: 1 week Sponsored by: Klara, Inc. Reviewed by: bnovkov, kevans Differential Revision: https://reviews.freebsd.org/D55483 (cherry picked from commit 7305604b29d3db29c9bb5de6e7a25829fb541d1e)
110 lines
3.1 KiB
Groff
110 lines
3.1 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd February 24, 2026
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.Dt SYSTEM 3
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.Os
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.Sh NAME
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.Nm system
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.Nd pass a command to the shell
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft int
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.Fn system "const char *string"
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.Sh DESCRIPTION
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The
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.Fn system
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function
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hands the argument
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.Fa string
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to the command interpreter
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.Xr sh 1 .
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The calling process waits for the shell
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to finish executing the command,
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ignoring
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.Dv SIGINT
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and
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.Dv SIGQUIT ,
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and blocking
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.Dv SIGCHLD .
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.Pp
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If
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.Fa string
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is a
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.Dv NULL
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pointer,
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.Fn system
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will return non-zero if the command interpreter
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.Xr sh 1
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is available, and zero if it is not.
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.Sh RETURN VALUES
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The
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.Fn system
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function
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returns the exit status of the shell as returned by
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.Xr waitpid 2 ,
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or \-1 if an error occurred when invoking
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.Xr fork 2
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or
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.Xr waitpid 2 .
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If the child process fails to execute the shell, it will terminate
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with an exit code of 127 and
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.Nm
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will return the corresponding exit status.
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.Sh SEE ALSO
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.Xr sh 1 ,
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.Xr execve 2 ,
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.Xr fork 2 ,
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.Xr waitpid 2 ,
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.Xr popen 3 ,
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.Xr posix_spawn 3
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.Sh STANDARDS
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The
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.Fn system
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function
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conforms to
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.St -isoC
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and is expected to be
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.St -p1003.2
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compatible.
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.Sh SECURITY CONSIDERATIONS
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The
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.Fn system
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function is easily misused in a manner that enables a malicious
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user to run arbitrary command,
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because all meta-characters supported by
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.Xr sh 1
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would be honored.
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User supplied parameters should always be carefully sanitized
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before they appear in
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.Fa string .
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