GETMNTOPTS(3) BSD Library Functions Manual GETMNTOPTS(3)NAMEgetmntopts — scan mount options
LIBRARY
System Utilities Library (libutil, -lutil)
SYNOPSIS
#include <mntopts.h>
mntoptparse_t
getmntopts(const char *options, const struct mntopt *mopts, int *flagp,
int *altflagp);
const char *
getmntoptstr(mntoptparse_t mp, const char *opt);
long
getmntoptnum(mntoptparse_t mp, const char *opt);
void
freemntopts(mntoptparse_t mp);
DESCRIPTION
The 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.
The string options is broken down into a sequence of comma separated
tokens. Each token is looked up in the table described by mopts and the
bits in the word referenced by either flagp or altflagp (depending on the
m_altloc field of the option's table entry) are updated. The flag words
are not initialized by getmntopts(). The table, mopts, has the following
format:
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 */
};
The members of this structure are:
m_option the option name, for example “suid”.
m_inverse tells getmntopts() that the name has the inverse meaning of
the bit. For example, “suid” is the string, whereas the mount
flag is MNT_NOSUID. In this case, the sense of the string and
the flag are inverted, so the m_inverse flag should be set.
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 “no”. The m_inverse flag causes these two opera‐
tions to be reversed.
m_altloc the bit should be set or cleared in altflagp rather than
flagp.
Each of the user visible MNT_ flags has a corresponding MOPT_ macro which
defines an appropriate struct mntopt entry. To simplify the program
interface and ensure consistency across all programs, a general purpose
macro, MOPT_STDOPTS, is defined which contains an entry for all the
generic VFS options. In addition, the macros MOPT_FORCE and MOPT_UPDATE
exist to enable the MNT_FORCE and MNT_UPDATE flags to be set. Finally,
the table must be terminated by an entry with a NULL first element.
getmntopts() returns a mntoptparse_t handle that can be used in subse‐
quent getmntoptstr() and getmntoptnum() calls to fetch a value for an
option and that must be freed with a call to freemntopts(). If an error
occurred, then if the external integer value getmnt_silent is zero then
getmntopts() prints an error message and exits; if getmnt_silent is non-
zero then getmntopts() returns NULL.
The 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 getmnt_silent is zero then
getmntoptstr() prints an error message and exits; if getmnt_silent is
non-zero then getmntoptstr() returns NULL.
The getmntoptnum() 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 getmnt_silent is zero then getmntoptnum() prints an error message
and exits; if getmnt_silent is non-zero then getmntoptnum() returns -1.
The freemntopts() frees the storage used by getmntopts().
RETURN VALUESgetmntopts() returns NULL if an error occurred. Note that some bits may
already have been set in flagp and altflagp even if NULL is returned.
getmntoptstr() returns NULL if an error occurred. getmntoptnum() returns
-1 if an error occurred.
EXAMPLES
Most commands will use the standard option set. Local filesystems which
support the MNT_UPDATE flag, would also have an MOPT_UPDATE entry. This
can be declared and used as follows:
#include <mntopts.h>
static const struct mntopt mopts[] = {
MOPT_STDOPTS,
MOPT_UPDATE,
{ NULL }
};
...
long val;
mntoptparse_t mp;
mntflags = mntaltflags = 0;
...
mp = getmntopts(options, mopts, &mntflags, &mntaltflags);
if (mp == NULL)
err(EXIT_FAILURE, "getmntopts");
...
val = getmntoptnum(mp, "rsize");
freemntopts(mp);
DIAGNOSTICS
If the external integer variable getmnt_silent is zero then the
getmntopts(), getmntoptstr(), and getmntoptnum() functions display an
error message and exit if an error occurred. By default getmnt_silent is
zero.
SEE ALSOerr(3), mount(8)HISTORY
The getmntopts() function appeared in 4.4BSD. It was moved to the utili‐
ties library and enhanced to retrieve option values in NetBSD 2.0.
BSD May 4, 2010 BSD
