281 lines
6.7 KiB
Groff
281 lines
6.7 KiB
Groff
.\" $NetBSD: getmntopts.3,v 1.14 2017/07/03 21:32:51 wiz Exp $
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.\"
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.\" Copyright (c) 1994
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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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.\" @(#)getmntopts.3 8.3 (Berkeley) 3/30/95
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.\"
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.Dd May 4, 2010
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.Dt GETMNTOPTS 3
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.Os
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.Sh NAME
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.Nm getmntopts ,
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.Nm getmntoptstr ,
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.Nm getmntoptnum ,
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.Nm freemntopts
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.Nd scan mount options
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.Sh LIBRARY
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.Lb libutil
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.Sh SYNOPSIS
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.In mntopts.h
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.Ft mntoptparse_t
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.Fn getmntopts "const char *options" "const struct mntopt *mopts" "int *flagp" "int *altflagp"
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.Ft const char *
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.Fn getmntoptstr "mntoptparse_t mp" "const char *opt"
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.Ft long
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.Fn getmntoptnum "mntoptparse_t mp" "const char *opt"
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.Ft void
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.Fn freemntopts "mntoptparse_t mp"
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.Sh DESCRIPTION
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The
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.Fn getmntopts
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function takes a comma separated option list and a list
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of valid option names, and computes the bitmasks
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corresponding to the requested set of options.
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.Pp
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The string
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.Ar options
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is broken down into a sequence of comma separated tokens.
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Each token is looked up in the table described by
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.Ar mopts
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and the bits in
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the word referenced by either
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.Ar flagp
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or
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.Ar altflagp
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(depending on the
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.Dv m_altloc
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field of the option's table entry)
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are updated.
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The flag words are not initialized by
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.Fn getmntopts .
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The table,
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.Ar mopts ,
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has the following format:
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.Bd -literal
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struct mntopt {
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const char *m_option; /* option name */
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int m_inverse; /* negative option, e.g., "dev" */
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int m_flag; /* bit to set, e.g., MNT_RDONLY */
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int m_altloc; /* use altflagp rather than flagp */
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};
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.Ed
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.Pp
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The members of this structure are:
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.Bl -tag -width m_inverse
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.It Fa m_option
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the option name,
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for example
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.Dq suid .
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.It Fa m_inverse
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tells
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.Fn getmntopts
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that the name has the inverse meaning of the bit.
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For example,
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.Dq suid
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is the string, whereas the mount flag is
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.Dv MNT_NOSUID .
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In this case, the sense of the string and the flag
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are inverted, so the
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.Fa m_inverse
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flag should be set.
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.It Fa m_flag
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the value of the bit to be set or cleared in
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the flag word when the option is recognized.
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The bit is set when the option is discovered,
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but cleared if the option name was preceded
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by the letters
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.Dq no .
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The
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.Fa m_inverse
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flag causes these two operations to be reversed.
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.It Fa m_altloc
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the bit should be set or cleared in
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.Ar altflagp
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rather than
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.Ar flagp .
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.El
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.Pp
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Each of the user visible
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.Dv MNT_
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flags has a corresponding
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.Dv MOPT_
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macro which defines an appropriate
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.Li "struct mntopt"
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entry.
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To simplify the program interface and ensure consistency across all
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programs, a general purpose macro,
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.Dv MOPT_STDOPTS ,
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is defined which contains an entry for all the generic VFS options.
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In addition, the macros
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.Dv MOPT_FORCE
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and
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.Dv MOPT_UPDATE
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exist to enable the
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.Dv MNT_FORCE
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and
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.Dv MNT_UPDATE
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flags to be set.
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Finally, the table must be terminated by an entry with a
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.Dv NULL
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first element.
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.Pp
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.Fn getmntopts
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returns a
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.Li "mntoptparse_t"
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handle that can be used in subsequent
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.Fn getmntoptstr
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and
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.Fn getmntoptnum
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calls to fetch a value for an option and that must be freed with a call
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to
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.Fn freemntopts .
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If an error occurred, then if the external integer value
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.Va getmnt_silent
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is zero then
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.Fn getmntopts
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prints an error message and exits;
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if
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.Va getmnt_silent
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is non-zero then
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.Fn getmntopts
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returns
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.Dv NULL .
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.Pp
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The
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.Fn getmntoptstr
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function returns the string value of the named option, if such a value
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was set in the option string.
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If the value was not set, then if the external integer value
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.Va getmnt_silent
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is zero then
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.Fn getmntoptstr
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prints an error message and exits;
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if
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.Va getmnt_silent
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is non-zero then
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.Fn getmntoptstr
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returns
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.Dv NULL .
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.Pp
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The
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.Fn getmntoptnum
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function returns the long value of the named option, if such a value was set in the
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option string.
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If the value was not set, or could not be converted from a string to a
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long, then if the external integer value
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.Va getmnt_silent
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is zero then
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.Fn getmntoptnum
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prints an error message and exits;
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if
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.Va getmnt_silent
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is non-zero then
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.Fn getmntoptnum
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returns \-1.
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.Pp
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The
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.Fn freemntopts
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function frees the storage used by
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.Fn getmntopts .
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.Sh RETURN VALUES
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.Fn getmntopts
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returns
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.Dv NULL
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if an error occurred.
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Note that some bits may already have been set in
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.Va flagp
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and
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.Va altflagp
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even if
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.Dv NULL
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is returned.
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.Fn getmntoptstr
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returns
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.Dv NULL
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if an error occurred.
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.Fn getmntoptnum
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returns \-1 if an error occurred.
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.Sh EXAMPLES
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Most commands will use the standard option set.
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Local filesystems which support the
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.Dv MNT_UPDATE
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flag, would also have an
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.Dv MOPT_UPDATE
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entry.
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This can be declared and used as follows:
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.Bd -literal -offset indent
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#include <mntopts.h>
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static const struct mntopt mopts[] = {
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MOPT_STDOPTS,
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MOPT_UPDATE,
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{ NULL }
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};
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\&...
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long val;
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mntoptparse_t mp;
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mntflags = mntaltflags = 0;
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\&...
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mp = getmntopts(options, mopts, &mntflags, &mntaltflags);
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if (mp == NULL)
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err(EXIT_FAILURE, "getmntopts");
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\&...
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val = getmntoptnum(mp, "rsize");
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freemntopts(mp);
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.Ed
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.Sh DIAGNOSTICS
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If the external integer variable
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.Va getmnt_silent
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is zero then the
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.Fn getmntopts ,
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.Fn getmntoptstr ,
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and
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.Fn getmntoptnum
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functions display an error message and exit if an error occurred.
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By default
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.Va getmnt_silent
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is zero.
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.Sh SEE ALSO
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.Xr err 3 ,
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.Xr mount 8
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.Sh HISTORY
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The
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.Fn getmntopts
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function appeared in
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.Bx 4.4 .
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It was moved to the utilities library and enhanced to retrieve option
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values in
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.Nx 2.0 .
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