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 *path, 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(int size;
                     FILE *restrict streamp,
                     struct mntent *restrict mntbuf,
                     char buf[restrict size], int size);

   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 path 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 size.

       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(), endmntent(), │ Thread safety │ MT-Safe                                                   │
       │ 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 6.16                               2025-06-28                                       getmntent(3)