 @@ -1,293 +1,292 @@
-.\"	$NetBSD: exec.3,v 1.30 2019/09/01 19:33:45 sevan Exp $
+.\"	$NetBSD: exec.3,v 1.31 2019/09/01 19:36:09 wiz Exp $
 .\"
 .\" Copyright (c) 1991, 1993
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 .\"
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 .\" modification, are permitted provided that the following conditions
 .\" are met:
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 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\" 3. Neither the name of the University nor the names of its contributors
 .\"    may be used to endorse or promote products derived from this software
 .\"    without specific prior written permission.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 .\"
 .\"     @(#)exec.3	8.3 (Berkeley) 1/24/94
 .\"
 .Dd September 1, 2019
 .Dt EXEC 3
 .Os
 .Sh NAME
 .Nm execl ,
 .Nm execlp ,
 .Nm execlpe ,
 .Nm execle ,
 .Nm exect ,
 .Nm execv ,
 .Nm execvp ,
 .Nm execvpe
 .Nd execute a file
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
 .In unistd.h
 .Vt extern char **environ;
 .Ft int
 .Fn execl "const char *path" "const char *arg" ...
 .Ft int
 .Fn execlp "const char *file" "const char *arg" ...
 .Ft int
 .Fn execlpe "const char *path" "const char *arg" ... "char *const envp[]"
 .Ft int
 .Fn execle "const char *path" "const char *arg" ... "char *const envp[]"
 .Ft int
 .Fn exect "const char *path" "char *const argv[]"  "char *const envp[]"
 .Ft int
 .Fn execv "const char *path" "char *const argv[]"
 .Ft int
 .Fn execvp "const char *file" "char *const argv[]"
 .Ft int
 .Fn execvpe "const char *file" "char *const argv[]" "char *const envp[]"
 .Sh DESCRIPTION
 The
 .Fn exec
 family of functions replaces the current process image with a
 new process image.
 The functions described in this manual page are front-ends for the function
 .Xr execve 2 .
 (See the manual page for
 .Xr execve 2
 for detailed information about the replacement of the current process.
 The
 .Xr script 7
 manual page provides detailed information about the execution of
 interpreter scripts.)
 .Pp
 The initial argument for these functions is the pathname of a file which
 is to be executed.
 .Pp
 The
 .Fa "const char *arg"
 and subsequent ellipses in the
 .Fn execl ,
 .Fn execlp ,
 .Fn execlpe ,
 and
 .Fn execle
 functions can be thought of as
 .Em arg0 ,
 .Em arg1 ,
 \&...,
 .Em argn .
 Together they describe a list of one or more pointers to NUL-terminated
 strings that represent the argument list available to the executed program.
 The first argument, by convention, should point to the file name associated
 with the file being executed.
 The list of arguments
 .Em must
 be terminated by a
 .Dv NULL
 pointer.
 .Pp
 The
 .Fn exect ,
 .Fn execv ,
 .Fn execvp ,
 and
 .Fn execvpe
 functions provide an array of pointers to NUL-terminated strings that
 represent the argument list available to the new program.
 The first argument, by convention, should point to the file name associated
 with the file being executed.
 The array of pointers
 .Sy must
 be terminated by a
 .Dv NULL
 pointer.
 .Pp
 The
 .Fn execle ,
 .Fn execlpe ,
 .Fn exect ,
 and
 .Fn execvpe
 functions also specify the environment of the executed process by following
 the
 .Dv NULL
 pointer that terminates the list of arguments in the parameter list
 or the pointer to the argv array with an additional parameter.
 This additional parameter is an array of pointers to NUL-terminated strings
 and
 .Em must
 be terminated by a
 .Dv NULL
 pointer.
 The other functions take the environment for the new process image from the
 external variable
 .Va environ
 in the current process.
 .Pp
 Some of these functions have special semantics.
 .Pp
 The functions
 .Fn execlp ,
 .Fn execlpe ,
 .Fn execvp ,
 and
 .Fn execvpe
 will duplicate the actions of the shell in searching for an executable file
 if the specified file name does not contain a slash
 .Dq Li \&/
 character.
 The search path is the path specified in the environment by the
 .Ev PATH
 variable.
 If this variable isn't specified,
 .Va _PATH_DEFPATH
 from
 .In paths.h
 is used instead, its value being:
 .Pa /usr/bin:/bin:/usr/pkg/bin:/usr/local/bin .
 In addition, certain errors are treated specially.
 .Pp
 If permission is denied for a file (the attempted
 .Xr execve 2
 returned
 .Er EACCES ) ,
 these functions will continue searching the rest of
 the search path.
 If no other file is found, however, they will return with the global variable
 .Va errno
 set to
 .Er EACCES .
 .Pp
 If the header of a file isn't recognized (the attempted
 .Xr execve 2
 returned
 .Er ENOEXEC ) ,
 these functions will execute the shell with the path of
 the file as its first argument.
 (If this attempt fails, no further searching is done.)
 .Pp
 If the file is currently busy (the attempted
 .Xr execve 2
 returned
 .Er ETXTBUSY ) ,
 these functions will sleep for several seconds,
 periodically re-attempting to execute the file.
 .Pp
 The function
 .Fn exect
 executes a file with the program tracing facilities enabled (see
 .Xr ptrace 2 ) .
 .Sh RETURN VALUES
 If any of the
 .Fn exec
 functions returns, an error will have occurred.
 The return value is \-1, and the global variable
 .Va errno
 will be set to indicate the error.
 .Sh FILES
 .Bl -tag -width /bin/sh -compact
 .It Pa /bin/sh
 The shell.
 .El
 .Sh COMPATIBILITY
 Historically, the default path for the
 .Fn execlp
 .Fn execlpe ,
 .Fn execvp ,
 and
 .Fn execvpe
 functions was
 .Dq Pa :/bin:/usr/bin .
 This was changed to improve security and behaviour.
 .Pp
 The behavior of
 .Fn execlp ,
 .Fn execlpe ,
 .Fn execvp ,
 and
 .Fn execvpe
 when errors occur while attempting to execute the file is historic
 practice, but has not traditionally been documented and is not specified
 by the POSIX standard.
 .Pp
 Traditionally, the functions
 .Fn execlp ,
 .Fn execlpe ,
 .Fn execvp ,
 and
 .Fn execvpe
 ignored all errors except for the ones described above and
 .Er ENOMEM
 and
 .Er E2BIG ,
 upon which they returned.
 They now return if any error other than the ones described above occurs.
 .Sh ERRORS
 .Fn execl ,
 .Fn execle ,
 .Fn execlp ,
 .Fn execlpe ,
 .Fn execvp ,
 and
 .Fn execvpe
 may fail and set
 .Va errno
 for any of the errors specified for the library functions
 .Xr execve 2
 and
 .Xr malloc 3 .
 .Pp
 .Fn exect
 and
 .Fn execv
 may fail and set
 .Va errno
 for any of the errors specified for the library function
 .Xr execve 2 .
 .Sh SEE ALSO
 .Xr sh 1 ,
 .Xr execve 2 ,
 .Xr fork 2 ,
 .Xr ptrace 2 ,
 .Xr environ 7 ,
 .Xr script 7
 .Sh STANDARDS
 .Fn execl ,
 .Fn execv ,
 .Fn execle ,
 .Fn execlp ,
 and
 .Fn execvp
 conform to
 .St -p1003.1-90 .
 .Pp
 .Sh HISTORY
 The
 .Fn exec
 function appeared in
 .At v1 .
 The
 .Fn execlpe
 function appeared first in QNX and the
 .Fn execvpe
 function exists on both
 .Nx
 and QNX.