Manpages - getmntent.3

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

  #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 *restrict buf, 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

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.

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.

/etc/fstab

filesystem description file

/etc/mtab

mounted filesystem description file

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

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*().

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

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