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Add a manpage for the kenv(2) syscall that Chad David kindly
wrote for me. Submitted by: davidc
This commit is contained in:
Maxime Henrion
parent
05a213f1e8
commit
ccee6a3c72
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=95003
172
lib/libc/sys/kenv.2
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172
lib/libc/sys/kenv.2
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.\"
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.\" Copyright (C) 2001 Chad David <davidc@FreeBSD.org>. 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(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), 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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" 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 SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 17, 2002
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.Dt KENV 2
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.Os
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.Sh NAME
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.Nm kenv
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.Nd kernel environment
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In kenv.h
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.Ft int
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.Fn kenv "int action" "const char *name" "char *value" "int len"
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.Sh DESCRIPTION
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The
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.Fn kenv
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function manipulates kernel environment variables.
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It supports the well known userland actions of getting, setting and unsetting
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environment variables, as well as the ability to dump all of the entries in
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the kernel environment.
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.Pp
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The
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.Fa action
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parameter can be one of the following:
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.Bl -tag -width ".Dv KENV_DUMP"
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.It Dv KENV_GET
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Returns the value associated with the named kernel environment variable.
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If the variable is not found -1 is returned and
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.Va errno
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is set to
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.Er ENOENT .
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Only the number of bytes available in
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.Fa value
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are copied out.
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.It Dv KENV_SET
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Sets or adds a new kernel environment variable.
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This option is only avaiable to the superuser.
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.It Dv KENV_UNSET
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Unsets the kernel environment variable
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.Fa name .
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If the variable does not exists -1 is returned and
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.Va errno
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is set to
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.Er EINVAL .
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This option is only available to the superuser.
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.It Dv KENV_DUMP
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Dumps as much of the kernel environment as will fit in
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.Fa value .
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If
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.Fa value
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is
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.Dv NULL ,
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.Fn kenv
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will return the number of bytes required to copy out the entire environment.
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.El
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.Pp
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The
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.Fa name
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parameter is the name of the environment variable to be affected.
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In the case of
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.Dv KENV_DUMP
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it is ignored.
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.Pp
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The
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.Fa value
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parameter contains either the value to set the environment variable
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.Fa name
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to in the case of
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.Dv KENV_SET ,
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or it points to the location where
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.Fn kenv
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should copy return data to in the case of
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.Dv KENV_DUMP
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and
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.Dv KENV_GET .
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If
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.Fa value
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is
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.Dv NULL
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in the case of
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.Dv KENV_DUMP ,
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.Fn kenv
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will return the number of bytes required to copy out the entire environment.
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.Pp
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The
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.Fa len
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parameter indicates how many bytes of storage
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.Fa value
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points to.
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.Sh RETURN VALUES
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The
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.Fn kenv
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function returns 0 if successful in the case of
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.Dv KENV_SET
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and
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.Dv KENV_UNSET,
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and the number of bytes copied into
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.Fa value
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in the case of
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.Dv KENV_DUMP
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and
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.Dv KENV_GET .
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If an error occurs, a value of -1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn kenv
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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.Fa action
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is not a valid option, or the length of the
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.Fa value
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is less than 1 for a
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.Dv KENV_SET .
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.It Bq Er ENOENT
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no value could be found for
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.Fa name
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for a
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.Dv KENV_SET
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or
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.Dv KENV_UNSET .
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.It Bq Er EPERM
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a user other than the superuser attempted to set or unset an kernel
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environment variable.
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.It Bq Er EFAULT
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a bad address was encountered while attempting to copy in user arguments,
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or copy out value(s).
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.It Bq Er ENAMETOOLONG
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the name of a variable supplied by the user is longer than
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.Dv KENV_MNAMELEN
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or the value of a variable is longer than
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.Dv KENV_MVALLEN .
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.El
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.Sh SEE ALSO
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.Xr kenv 1
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.Sh AUTHORS
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.An -nosplit
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This man page was written by
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.An Chad David Aq davidc@FreeBSD.org .
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.Pp
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The
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.Fn kenv
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system call was written by
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.An Maxime Henrion Aq mux@FreeBSD.org .
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