getmntent(), 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(5)).

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 getmntany() 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 mnttab file has been reopened or rewound since a previous getextmntent() call. This notification is accomplished by calling resetmnttab(). Otherwise, 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. Substrings 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The putmntent() function is obsolete and no longer has any effect.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 function 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(5)). 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().

getmntent(), 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 substring if a match is found. Otherwise, it returns 0.

putmntent()

The putmntent() is obsolete and always returns −1.