1getmntent(3)               Library Functions Manual               getmntent(3)
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3
4

NAME

6       getmntent,  setmntent,  addmntent,  endmntent, hasmntopt, getmntent_r -
7       get filesystem descriptor file entry
8

LIBRARY

10       Standard C library (libc, -lc)
11

SYNOPSIS

13       #include <stdio.h>
14       #include <mntent.h>
15
16       FILE *setmntent(const char *filename, const char *type);
17
18       struct mntent *getmntent(FILE *stream);
19
20       int addmntent(FILE *restrict stream,
21                     const struct mntent *restrict mnt);
22
23       int endmntent(FILE *streamp);
24
25       char *hasmntopt(const struct mntent *mnt, const char *opt);
26
27       /* GNU extension */
28       #include <mntent.h>
29
30       struct mntent *getmntent_r(FILE *restrict streamp,
31                     struct mntent *restrict mntbuf,
32                     char buf[restrict .buflen], int buflen);
33
34   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
35
36       getmntent_r():
37           Since glibc 2.19:
38               _DEFAULT_SOURCE
39           glibc 2.19 and earlier:
40               _BSD_SOURCE || _SVID_SOURCE
41

DESCRIPTION

43       These routines are used  to  access  the  filesystem  description  file
44       /etc/fstab and the mounted filesystem description file /etc/mtab.
45
46       The setmntent() function opens the filesystem description file filename
47       and returns a file pointer which can be used by getmntent().  The argu‐
48       ment  type  is the type of access required and can take the same values
49       as the mode argument of fopen(3).  The returned stream should be closed
50       using endmntent() rather than fclose(3).
51
52       The getmntent() function reads the next line of the filesystem descrip‐
53       tion file from stream and returns a pointer to a  structure  containing
54       the broken out fields from a line in the file.  The pointer points to a
55       static area of memory which is overwritten by subsequent calls to getm‐
56       ntent().
57
58       The  addmntent()  function  adds the mntent structure mnt to the end of
59       the open stream.
60
61       The endmntent() function closes the stream associated with the filesys‐
62       tem description file.
63
64       The  hasmntopt()  function  scans the mnt_opts field (see below) of the
65       mntent structure mnt for a substring that matches opt.  See  <mntent.h>
66       and mount(8) for valid mount options.
67
68       The  reentrant  getmntent_r()  function  is similar to getmntent(), but
69       stores the mntent structure in the provided  *mntbuf,  and  stores  the
70       strings pointed to by the entries in that structure in the provided ar‐
71       ray buf of size buflen.
72
73       The mntent structure is defined in <mntent.h> as follows:
74
75           struct mntent {
76               char *mnt_fsname;   /* name of mounted filesystem */
77               char *mnt_dir;      /* filesystem path prefix */
78               char *mnt_type;     /* mount type (see mntent.h) */
79               char *mnt_opts;     /* mount options (see mntent.h) */
80               int   mnt_freq;     /* dump frequency in days */
81               int   mnt_passno;   /* pass number on parallel fsck */
82           };
83
84       Since fields in the mtab and fstab files are separated  by  whitespace,
85       octal  escapes  are  used to represent the characters space (\040), tab
86       (\011), newline (\012), and backslash (\\) in those files when they oc‐
87       cur in one of the four strings in a mntent structure.  The routines ad‐
88       dmntent() and getmntent() will convert from  string  representation  to
89       escaped  representation  and back.  When converting from escaped repre‐
90       sentation, the sequence \134 is also converted to a backslash.
91

RETURN VALUE

93       The getmntent() and getmntent_r() functions return a pointer to the mn‐
94       tent structure or NULL on failure.
95
96       The addmntent() function returns 0 on success and 1 on failure.
97
98       The endmntent() function always returns 1.
99
100       The  hasmntopt()  function  returns  the  address of the substring if a
101       match is found and NULL otherwise.
102

FILES

104       /etc/fstab
105              filesystem description file
106
107       /etc/mtab
108              mounted filesystem description file
109

ATTRIBUTES

111       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
112       tributes(7).
113
114       ┌──────────────┬───────────────┬───────────────────────────────────────┐
115Interface     Attribute     Value                                 
116       ├──────────────┼───────────────┼───────────────────────────────────────┤
117setmntent(),  │ Thread safety │ MT-Safe                               │
118endmntent(),  │               │                                       │
119hasmntopt()   │               │                                       │
120       ├──────────────┼───────────────┼───────────────────────────────────────┤
121getmntent()   │ Thread safety │ MT-Unsafe race:mntentbuf locale       │
122       ├──────────────┼───────────────┼───────────────────────────────────────┤
123addmntent()   │ Thread safety │ MT-Safe race:stream locale            │
124       ├──────────────┼───────────────┼───────────────────────────────────────┤
125getmntent_r() │ Thread safety │ MT-Safe locale                        │
126       └──────────────┴───────────────┴───────────────────────────────────────┘
127

STANDARDS

129       None.
130

HISTORY

132       The  nonreentrant  functions  are  from  SunOS 4.1.3.  A routine getmn‐
133       tent_r() was introduced in HP-UX 10, but it returns an int.  The proto‐
134       type shown above is glibc-only.
135
136       System  V also has a getmntent() function but the calling sequence dif‐
137       fers,  and  the  returned  structure  is  different.   Under  System  V
138       /etc/mnttab  is used.  4.4BSD and Digital UNIX have a routine getmntin‐
139       fo(), a wrapper around the system call getfsstat().
140

SEE ALSO

142       fopen(3), fstab(5), mount(8)
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146Linux man-pages 6.04              2023-03-30                      getmntent(3)
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