2.9BSD/usr/man/man5/mtab.5

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.TH MTAB 5 
.UC
.SH NAME
mtab \- mounted file system table
.SH SYNOPSIS
.B #include <mtab.h>
.SH DESCRIPTION
.I Mtab
resides in directory
.I /etc
and contains a table of devices mounted by the
.IR mount (8)
command.
.IR Umount (8)
removes entries.
.PP
The format of a mount table entry, as given by the include file, is:
.PP
.nf
.ta 8n +9n +11n +11n +11n +11n
#define	MAXMOUNT	16
#define	PATHSIZE	32
#define	DEVSIZE		32
#define	MOUNTTABLE	"/etc/mtab"
struct	mtab {
	dev_t	m_dev;		/* major/minor device numbers */
	char	m_dname[DEVSIZE];	/* block device pathname */
	char	m_name[PATHSIZE];	/* mounted on pathname */
};
.fi
.PP
The special file has all its directories
stripped away;
that is, everything through the last `/' is thrown
away.
.PP
This table is present only so people can look at it.
It does not matter to
.I mount
if there are duplicated entries nor
to
.I umount
if a name cannot be found.
.SH FILES
/etc/mtab
.SH "SEE ALSO"
fstab(5), mount(8)