getmntent(3)               Library Functions Manual               getmntent(3)

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

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #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 feature_test_macros(7)):

       getmntent_r():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
       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
       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
       /etc/fstab
              filesystem description file

       /etc/mtab
              mounted filesystem description file

ATTRIBUTES
       For an explanation of the terms used in this section, see
       attributes(7).

       +---------------+---------------+--------------------------------------+
       |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
       None.

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

Linux man-pages 6.7               2023-10-31                      getmntent(3)