getmntent, setmntent, addmntent, endmntent, hasmntopt, getmntent_r — get file system descriptor file entry
#include <stdio.h> #include <mntent.h>
FILE
*setmntent( |
const char * | filename, |
const char * | type) ; |
struct mntent *getmntent( |
FILE * | fp) ; |
int
addmntent( |
FILE * | fp, |
const struct mntent * | mnt) ; |
int
endmntent( |
FILE * | fp) ; |
char
*hasmntopt( |
const struct mntent * | mnt, |
const char * | opt) ; |
/* GNU extension */ #define _GNU_SOURCE /* or _SVID_SOURCE or _BSD_SOURCE */ #include <mntent.h>
struct mntent *getmntent_r( |
FILE * | fp, |
struct mntent * | mntbuf, | |
char * | buf, | |
int | buflen) ; |
These routines are used to access the file system
description file /etc/fstab
and
the mounted file system description file /etc/mtab
.
The setmntent
() function
opens the file system description file fp
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 getmntent
() function
reads the next line from the file system description file
fp
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 file
fp
.
The endmntent
() function
closes the file system description file fp
.
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 file system */ char * mnt_dir
;/* file system 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 four
characters space (\040), tab (\011), newline (\012) and
backslash (\134) 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.
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.
The non-reentrant 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. LSB deprecates the functions
endhostent
(), sethostent
() and setmntent
().
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), feature_test_macros(7), mount(8)
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