GETMNTENT(3C)GETMNTENT(3C)NAME
getmntent, getmntany, getextmntent, hasmntopt, putmntent, resetmnttab -
get mounted device information
SYNOPSIS
#include <stdio.h>
#include <sys/mnttab.h>
int getmntent(FILE *fp, struct mnttab *mp);
int getmntany(FILE *fp, struct mnttab *mp, struct mnttab *mpref);
int getextmntent(FILE *fp, struct extmnttab *mp, int len);
char *hasmntopt(struct mnttab *mnt, char *opt);
int putmntent(FILE *iop, struct mnttab *mp);
void resetmnttab(FILE *fp);
DESCRIPTIONgetmntent() and getmntany()
The getmntent() and getmntany() functions each fill in the structure
pointed to by mp with the broken-out fields of a line in the mnttab
file. Each line read from the file contains a mnttab structure, which
is defined in the <sys/mnttab.h> header. The structure contains the
following members, which correspond to the broken-out fields from a
line in /etc/mnttab (see mnttab(4)).
char *mnt_special; /* name of mounted resource */
char *mnt_mountp; /* mount point */
char *mnt_fstype; /* type of file system mounted */
char *mnt_mntopts; /* options for this mount */
char *mnt_time; /* time file system mounted */
Fields with no actual content in /etc/mnttab are represented in the
file as "-". To clearly distinguish empty fields, getmntent() set the
corresponding field in mp to NULL.
Each getmntent() call causes a new line to be read from the mnttab
file. Successive calls can be used to search the entire list. The getm‐
ntany() function searches the file referenced by fp until a match is
found between a line in the file and mpref. A match occurs if all non-
null entries in mpref match the corresponding fields in the file.
These functions do not open, close, or rewind the file.
getextmntent()
The getextmntent() function is an extended version of the getmntent()
function that returns, in addition to the information that getmntent()
returns, the major and minor number of the mounted resource to which
the line in mnttab corresponds. The getextmntent() function also fills
in the extmntent structure defined in the <sys/mnttab.h> header. For
getextmntent() to function properly, it must be notified when the mnt‐
tab file has been reopened or rewound since a previous getextmntent()
call. This notification is accomplished by calling resetmnttab(). Oth‐
erwise, it behaves exactly as getmntent() described above
The data pointed to by the mnttab structure members are stored in a
static area and must be copied to be saved between successive calls.
hasmntopt()
The hasmntopt() function scans the mnt_mntopts member of the mnttab
structure mnt for a substring that matches opt. It returns the address
of the substring if a match is found; otherwise it returns 0. Sub‐
strings are delimited by commas and the end of the mnt_mntopts string.
putmntent()
The putmntent() function is obsolete and no longer has any effect.
Entries appear in mnttab as a side effect of a mount(2) call. The func‐
tion name is still defined for transition purposes.
resetmnttab()
The resetmnttab() function notifies getextmntent() to reload from the
kernel the device information that corresponds to the new snapshot of
the mnttab information (see mnttab(4)). Subsequent getextmntent() calls
then return correct extmnttab information. This function should be
called whenever the mnttab file is either rewound or closed and
reopened before any calls are made to getextmntent().
RETURN VALUESgetmntent() and getmntany()
If the next entry is successfully read by getmntent() or a match is
found with getmntany(), 0 is returned. If an EOF is encountered on
reading, these functions return −1. If an error is encountered, a value
greater than 0 is returned. The following error values are defined in
<sys/mnttab.h>:
MNT_TOOLONG
A line in the file exceeded the internal buffer size of
MNT_LINE_MAX.
MNT_TOOMANY
A line in the file contains too many fields.
MNT_TOOFEW
A line in the file contains too few fields.
hasmntopt()
Upon successful completion, hasmntopt() returns the address of the sub‐
string if a match is found. Otherwise, it returns 0.
putmntent()
The putmntent() is obsolete and always returns −1.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT-Level │ Safe │
└───────────────┴─────────────────┘
SEE ALSOmount(2), mnttab(4), attributes(5)
Mar 22, 2004 GETMNTENT(3C)
