setmntent(3) — Linux manual page


GETMNTENT(3)              Linux Programmer's Manual             GETMNTENT(3)

NAME         top

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

SYNOPSIS         top

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

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

       struct mntent *getmntent(FILE *stream);

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

       int endmntent(FILE *streamp);

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

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

       struct mntent *getmntent_r(FILE *streamp, struct mntent *mntbuf,
                                  char *buf, int buflen);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           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 struct mount in the provided *mntbuf and stores the
       strings pointed to by the entries in that struct 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                  │

CONFORMING TO         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.

NOTES         top

       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

       This page is part of release 5.09 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

                                 2019-03-06                     GETMNTENT(3)