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