getmntent(3) — Linux manual page


getmntent(3)            Library Functions Manual            getmntent(3)

NAME         top

       getmntent, setmntent, addmntent, endmntent, hasmntopt,
       getmntent_r - get filesystem descriptor file entry

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <stdio.h>
       #include <mntent.h>

       FILE *setmntent(const char *filename, const char *type);

       struct mntent *getmntent(FILE *stream);

       int addmntent(FILE *restrict stream,
                     const struct mntent *restrict mnt);

       int endmntent(FILE *streamp);

       char *hasmntopt(const struct mntent *mnt, const char *opt);

       /* GNU extension */
       #include <mntent.h>

       struct mntent *getmntent_r(FILE *restrict streamp,
                     struct mntent *restrict mntbuf,
                     char buf[restrict .buflen], int buflen);

   Feature Test Macro Requirements for glibc (see

           Since glibc 2.19:
           glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       These routines are used to access the filesystem description file
       /etc/fstab and the mounted filesystem description file /etc/mtab.

       The setmntent() function opens the filesystem description file
       filename and returns a file pointer which can be used by
       getmntent().  The argument type is the type of access required
       and can take the same values as the mode argument of fopen(3).
       The returned stream should be closed using endmntent() rather
       than fclose(3).

       The getmntent() function reads the next line of the filesystem
       description file from stream and returns a pointer to a structure
       containing the broken out fields from a line in the file.  The
       pointer points to a static area of memory which is overwritten by
       subsequent calls to getmntent().

       The addmntent() function adds the mntent structure mnt to the end
       of the open stream.

       The endmntent() function closes the stream associated with the
       filesystem description file.

       The hasmntopt() function scans the mnt_opts field (see below) of
       the mntent structure mnt for a substring that matches opt.  See
       <mntent.h> and mount(8) for valid mount options.

       The reentrant getmntent_r() function is similar to getmntent(),
       but stores the mntent structure in the provided *mntbuf, and
       stores the strings pointed to by the entries in that structure in
       the provided array buf of size buflen.

       The mntent structure is defined in <mntent.h> as follows:

           struct mntent {
               char *mnt_fsname;   /* name of mounted filesystem */
               char *mnt_dir;      /* filesystem path prefix */
               char *mnt_type;     /* mount type (see mntent.h) */
               char *mnt_opts;     /* mount options (see mntent.h) */
               int   mnt_freq;     /* dump frequency in days */
               int   mnt_passno;   /* pass number on parallel fsck */

       Since fields in the mtab and fstab files are separated by
       whitespace, octal escapes are used to represent the characters
       space (\040), tab (\011), newline (\012), and backslash (\\) in
       those files when they occur in one of the four strings in a
       mntent structure.  The routines addmntent() and getmntent() will
       convert from string representation to escaped representation and
       back.  When converting from escaped representation, the sequence
       \134 is also converted to a backslash.

RETURN VALUE         top

       The getmntent() and getmntent_r() functions return a pointer to
       the mntent structure or NULL on failure.

       The addmntent() function returns 0 on success and 1 on failure.

       The endmntent() function always returns 1.

       The hasmntopt() function returns the address of the substring if
       a match is found and NULL otherwise.

FILES         top

              filesystem description file

              mounted filesystem description file

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ Interface     Attribute     Value                         │
       │ setmntent(),  │ Thread safety │ MT-Safe                       │
       │ endmntent(),  │               │                               │
       │ hasmntopt()   │               │                               │
       │ getmntent()   │ Thread safety │ MT-Unsafe race:mntentbuf      │
       │               │               │ locale                        │
       │ addmntent()   │ Thread safety │ MT-Safe race:stream locale    │
       │ getmntent_r() │ Thread safety │ MT-Safe locale                │

STANDARDS         top


HISTORY         top

       The nonreentrant functions are from SunOS 4.1.3.  A routine
       getmntent_r() was introduced in HP-UX 10, but it returns an int.
       The prototype shown above is glibc-only.

       System V also has a getmntent() function but the calling sequence
       differs, and the returned structure is different.  Under System V
       /etc/mnttab is used.  4.4BSD and Digital UNIX have a routine
       getmntinfo(), a wrapper around the system call getfsstat().

SEE ALSO         top

       fopen(3), fstab(5), mount(8)

COLOPHON         top

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Linux man-pages 6.9.1          2024-06-15                   getmntent(3)

Pages that refer to this page: getfsent(3)fstab(5)