getmntopts man page on 4.4BSD

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GETMNTOPTS(3)		 BSD Library Functions Manual		 GETMNTOPTS(3)

NAME
     getmntopts — scan mount options

SYNOPSIS
     #include <mntopts.h>

     void
     getmntopts(char *options, struct mntopt *mopts, int *flagp,
	 int *altflagp);

DESCRIPTION
     The getmntopts function takes a comma separated option list and a list of
     valid option names, and computes the bitmask 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 getmntopt.	The table, mopts, has the following
     format:

     struct mntopt {
	     char *m_option;	     /* option name */
	     int m_inverse;	     /* is this a negative option, eg "dev" */
	     int m_flag;	     /* bit to set, eg MNT_RDONLY */
	     int m_altloc;	     /* non-zero to 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.

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"

     struct mntopt mopts[] = {
	     MOPT_STDOPTS,
	     MOPT_UPDATE,
	     { NULL }
     };

	     ...
	     mntflags = mntaltflags = 0;
	     ...
	     getmntopts(options, mopts, &mntflags, &mntaltflags);
	     ...

DIAGNOSTICS
     If the external integer variable getmnt_silent is non-zero then the
     getmntopts function displays an error message and exits if an unrecog‐
     nized option is encountered.  By default getmnt_silent is zero.

SEE ALSO
     err(3), mount(8)

HISTORY
     The getmntopts() function appeared in 4.4BSD.

4.4BSD				March 30, 1995				4.4BSD
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