minix/lib/libc/gen/exec.3
Ben Gras 2fe8fb192f Full switch to clang/ELF. Drop ack. Simplify.
There is important information about booting non-ack images in
docs/UPDATING. ack/aout-format images can't be built any more, and
booting clang/ELF-format ones is a little different. Updating to the
new boot monitor is recommended.

Changes in this commit:

	. drop boot monitor -> allowing dropping ack support
	. facility to copy ELF boot files to /boot so that old boot monitor
	  can still boot fairly easily, see UPDATING
	. no more ack-format libraries -> single-case libraries
	. some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases
	. drop several ack toolchain commands, but not all support
	  commands (e.g. aal is gone but acksize is not yet).
	. a few libc files moved to netbsd libc dir
	. new /bin/date as minix date used code in libc/
	. test compile fix
	. harmonize includes
	. /usr/lib is no longer special: without ack, /usr/lib plays no
	  kind of special bootstrapping role any more and bootstrapping
	  is done exclusively through packages, so releases depend even
	  less on the state of the machine making them now.
	. rename nbsd_lib* to lib*
	. reduce mtree
2012-02-14 14:52:02 +01:00

262 lines
6.8 KiB
Groff

.\" $NetBSD: exec.3,v 1.21 2010/03/22 19:30:53 joerg Exp $
.\"
.\" Copyright (c) 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" 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
.\" SUCH DAMAGE.
.\"
.\" @(#)exec.3 8.3 (Berkeley) 1/24/94
.\"
.Dd May 6, 2005
.Dt EXEC 3
.Os
.Sh NAME
.Nm execl ,
.Nm execlp ,
.Nm execle ,
.Nm exect ,
.Nm execv ,
.Nm execvp
.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 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[]"
.Sh DESCRIPTION
The
.Nm 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 ,
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 null-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 ,
and
.Fn execvp
functions provide an array of pointers to null-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
and
.Fn exect
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 null-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
and
.Fn execvp
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
.Nm 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 ERRORS
.Fn execl ,
.Fn execle ,
.Fn execlp
and
.Fn execvp
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 COMPATIBILITY
Historically, the default path for the
.Fn execlp
and
.Fn execvp
functions was
.Dq Pa :/bin:/usr/bin .
This was changed to improve security and behaviour.
.Pp
The behavior of
.Fn execlp
and
.Fn execvp
when errors occur while attempting to execute the file is historic
practice, but has not traditionally been documented and is not specified
by the
.Tn POSIX
standard.
.Pp
Traditionally, the functions
.Fn execlp
and
.Fn execvp
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 STANDARDS
.Fn execl ,
.Fn execv ,
.Fn execle ,
.Fn execlp
and
.Fn execvp
conform to
.St -p1003.1-90 .