00c101b17d
For this, things are complicated. The first mention in the manual was in the 4th edition manual (as an add on to exec(II)). The 2nd and 3rd editions didn't have these in the manual (either as a separate page, or as an add-on to exec(II)). We don't have good 1st, 2nd or 3rd edition distributions to look in. However, there's a tape labeled 'last1120c' that we do have. This tape contains the last version of the V2 edition of the C compiler on it (just after C got struct). On this tape there was a libc.sa archive that contains source for execl and execp. This source is sufficiently different from the V5 sources (which are the next ones we have sources for) and have a slightly different calling convention than later sources, suggesting that the early date for the last1120c tape is correct (in that era, the epoch changed every year, leading to a one or two year ambiguity on when the files could have been modified) and it should be though of as V2. Since this was also a time of compiler development, and the calling convetions are known to be under evolution, and since the rest of the sources in libc.sa are consistent, that's further evidence that V2 is likely. Finally, 2nd edition was the last version to fully support the 11/20 because it lacked many basic features and bell labs moved off it to the 11/45 as soon as they could afford to buy one, around this time era. The unix manuals make it sound like V3 might have supported the 11/20, but the same intro could also be read to mean it didn't, at all, and that V3 was the first rewrite for the 11/45 ahead of the rewrite in C that came with V4. Taken together, the evidence leans most heavily to V2 (90% IMHO), and slightly to V3 (8%) or possibly V4 (2%). I've not put all this in the man page, but have left it here in case someone notices in the future that V4 is the first manual page for it.
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380 lines
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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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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.\" @(#)exec.3 8.3 (Berkeley) 1/24/94
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.\" $FreeBSD$
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.\"
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.Dd March 22, 2020
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.Dt EXEC 3
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.Os
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.Sh NAME
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.Nm execl ,
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.Nm execlp ,
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.Nm execle ,
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.Nm exect ,
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.Nm execv ,
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.Nm execvp ,
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.Nm execvP
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.Nd execute a file
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Vt extern char **environ ;
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.Ft int
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.Fn execl "const char *path" "const char *arg" ... NULL
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.Ft int
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.Fn execlp "const char *file" "const char *arg" ... NULL
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.Ft int
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.Fn execle "const char *path" "const char *arg" ... NULL "char *const envp[]"
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.Fc
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.Ft int
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.Fn exect "const char *path" "char *const argv[]" "char *const envp[]"
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.Ft int
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.Fn execv "const char *path" "char *const argv[]"
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.Ft int
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.Fn execvp "const char *file" "char *const argv[]"
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.Ft int
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.Fn execvP "const char *file" "const char *search_path" "char *const argv[]"
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.Sh DESCRIPTION
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The
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.Nm exec
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family of functions replaces the current process image with a
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new process image.
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The functions described in this manual page are front-ends for the function
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.Xr execve 2 .
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(See the manual page for
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.Xr execve 2
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for detailed information about the replacement of the current process.)
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.Pp
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The initial argument for these functions is the pathname of a file which
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is to be executed.
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.Pp
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The
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.Fa "const char *arg"
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and subsequent ellipses in the
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.Fn execl ,
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.Fn execlp ,
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and
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.Fn execle
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functions can be thought of as
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.Em arg0 ,
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.Em arg1 ,
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\&...,
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.Em argn .
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Together they describe a list of one or more pointers to null-terminated
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strings that represent the argument list available to the executed program.
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The first argument, by convention, should point to the file name associated
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with the file being executed.
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The list of arguments
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.Em must
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be terminated by a
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.Dv NULL
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pointer.
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.Pp
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The
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.Fn exect ,
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.Fn execv ,
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.Fn execvp ,
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and
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.Fn execvP
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functions provide an array of pointers to null-terminated strings that
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represent the argument list available to the new program.
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The first argument, by convention, should point to the file name associated
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with the file being executed.
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The array of pointers
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.Sy must
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be terminated by a
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.Dv NULL
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pointer.
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.Pp
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The
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.Fn execle
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and
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.Fn exect
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functions also specify the environment of the executed process by following
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the
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.Dv NULL
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pointer that terminates the list of arguments in the argument list
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or the pointer to the argv array with an additional argument.
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This additional argument is an array of pointers to null-terminated strings
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and
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.Em must
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be terminated by a
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.Dv NULL
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pointer.
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The other functions take the environment for the new process image from the
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external variable
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.Va environ
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in the current process.
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.Pp
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Some of these functions have special semantics.
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.Pp
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The functions
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.Fn execlp ,
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.Fn execvp ,
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and
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.Fn execvP
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will duplicate the actions of the shell in searching for an executable file
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if the specified file name does not contain a slash
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.Dq Li /
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character.
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For
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.Fn execlp
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and
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.Fn execvp ,
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search path is the path specified in the environment by
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.Dq Ev PATH
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variable.
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If this variable is not specified,
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the default path is set according to the
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.Dv _PATH_DEFPATH
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definition in
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.In paths.h ,
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which is set to
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.Dq Ev /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin .
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For
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.Fn execvP ,
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the search path is specified as an argument to the function.
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In addition, certain errors are treated specially.
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.Pp
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If an error is ambiguous (for simplicity, we shall consider all
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errors except
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.Er ENOEXEC
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as being ambiguous here, although only the critical error
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.Er EACCES
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is really ambiguous),
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then these functions will act as if they stat the file to determine
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whether the file exists and has suitable execute permissions.
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If it does, they will return immediately with the global variable
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.Va errno
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restored to the value set by
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.Fn execve .
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Otherwise, the search will be continued.
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If the search completes without performing a successful
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.Fn execve
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or terminating due to an error,
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these functions will return with the global variable
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.Va errno
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set to
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.Er EACCES
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or
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.Er ENOENT
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according to whether at least one file with suitable execute permissions
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was found.
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.Pp
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If the header of a file is not recognized (the attempted
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.Fn execve
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returned
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.Er ENOEXEC ) ,
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these functions will execute the shell with the path of
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the file as its first argument.
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(If this attempt fails, no further searching is done.)
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.Pp
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The function
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.Fn exect
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executes a file with the program tracing facilities enabled (see
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.Xr ptrace 2 ) .
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.Sh RETURN VALUES
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If any of the
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.Fn exec
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functions returns, an error will have occurred.
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The return value is \-1, and the global variable
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.Va errno
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will be set to indicate the error.
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.Sh FILES
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.Bl -tag -width /bin/sh -compact
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.It Pa /bin/sh
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The shell.
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.El
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.Sh COMPATIBILITY
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Historically, the default path for the
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.Fn execlp
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and
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.Fn execvp
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functions was
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.Dq Pa :/bin:/usr/bin .
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This was changed to remove the current directory to enhance system
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security.
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.Pp
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The behavior of
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.Fn execlp
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and
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.Fn execvp
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when errors occur while attempting to execute the file is not quite historic
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practice, and has not traditionally been documented and is not specified
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by the
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.Tn POSIX
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standard.
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.Pp
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Traditionally, the functions
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.Fn execlp
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and
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.Fn execvp
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ignored all errors except for the ones described above and
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.Er ETXTBSY ,
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upon which they retried after sleeping for several seconds, and
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.Er ENOMEM
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and
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.Er E2BIG ,
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upon which they returned.
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They now return for
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.Er ETXTBSY ,
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and determine existence and executability more carefully.
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In particular,
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.Er EACCES
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for inaccessible directories in the path prefix is no longer
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confused with
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.Er EACCES
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for files with unsuitable execute permissions.
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In
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.Bx 4.4 ,
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they returned upon all errors except
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.Er EACCES ,
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.Er ENOENT ,
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.Er ENOEXEC
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and
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.Er ETXTBSY .
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This was inferior to the traditional error handling,
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since it breaks the ignoring of errors for path prefixes
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and only improves the handling of the unusual ambiguous error
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.Er EFAULT
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and the unusual error
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.Er EIO .
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The behaviour was changed to match the behaviour of
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.Xr sh 1 .
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.Sh ERRORS
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The
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.Fn execl ,
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.Fn execle ,
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.Fn execlp ,
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.Fn execvp
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and
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.Fn execvP
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functions
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may fail and set
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.Va errno
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for any of the errors specified for the library functions
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.Xr execve 2
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and
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.Xr malloc 3 .
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.Pp
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The
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.Fn exect
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and
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.Fn execv
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functions
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may fail and set
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.Va errno
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for any of the errors specified for the library function
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.Xr execve 2 .
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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 ktrace 2 ,
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.Xr ptrace 2 ,
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.Xr environ 7
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.Sh STANDARDS
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The
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.Fn execl ,
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.Fn execv ,
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.Fn execle ,
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.Fn execlp
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and
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.Fn execvp
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functions
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conform to
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.St -p1003.1-88 .
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.Sh HISTORY
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The
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.Fn exec
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function appeared in
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.At v1 .
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The
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.Fn execl
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and
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.Fn execv
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functions appeared in
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.At v2 .
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The
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.Fn execvP
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function first appeared in
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.Fx 5.2 .
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.Sh BUGS
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The type of the
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.Fa argv
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and
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.Fa envp
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parameters to
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.Fn execle ,
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.Fn exect ,
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.Fn execv ,
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.Fn execvp ,
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and
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.Fn execvP
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is a historical accident and no sane implementation should modify the provided
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strings.
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The bogus parameter types trigger false positives from
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.Li const
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correctness analyzers.
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On
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.Fx ,
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the
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.Fn __DECONST
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macro may be used to work around this limitation.
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.Pp
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Due to a fluke of the C standard, on platforms other than
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.Fx
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the definition of
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.Dv NULL
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may be the untyped number zero, rather than a
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.Ad (void *)0
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expression.
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To distinguish the concepts, they are referred to as a
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.Dq null pointer constant
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and a
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.Dq null pointer ,
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respectively.
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On exotic computer architectures that
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.Fx
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does not support, the null pointer constant and null pointer may have a
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different representation.
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In general, where this document and others reference a
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.Dv NULL
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value, they actually imply a null pointer.
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E.g., for portability to non-FreeBSD operating systems on exotic computer
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architectures, one may use
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.Li (char *)NULL
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in place of
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.Dv NULL
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when invoking
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.Fn execl ,
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.Fn execle ,
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and
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.Fn execlp .
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