man3/getmntent.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified Sat Jul 24 21:46:57 1993 by Rik Faith (faith@cs.unc.edu)
  30 .\" Modified 961109, 031115, aeb
  31 .\"
  32 .TH GETMNTENT 3  2017-09-15 "" "Linux Programmer's Manual"
  33 .SH NAME
  34 getmntent, setmntent, addmntent, endmntent, hasmntopt,
  35 getmntent_r \- get filesystem descriptor file entry
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <stdio.h>
  39 .B #include <mntent.h>
  40 .PP
  41 .BI "FILE *setmntent(const char *" filename ", const char *" type );
  42 .PP
  43 .BI "struct mntent *getmntent(FILE *" stream );
  44 .PP
  45 .BI "int addmntent(FILE *" stream ", const struct mntent *" mnt );
  46 .PP
  47 .BI "int endmntent(FILE *" streamp );
  48 .PP
  49 .BI "char *hasmntopt(const struct mntent *" mnt ", const char *" opt );
  50
  51 /* GNU extension */
  52 .B #include <mntent.h>
  53 .PP
  54 .BI "struct mntent *getmntent_r(FILE *" streamp ", struct mntent *" mntbuf ,
  55 .BI "                           char *" buf ", int " buflen );
  56 .fi
  57 .PP
  58 .in -4n
  59 Feature Test Macro Requirements for glibc (see
  60 .BR feature_test_macros (7)):
  61 .in
  62 .PP
  63 .BR getmntent_r ():
  64     Since glibc 2.19:
  65         _DEFAULT_SOURCE
  66     Glibc 2.19 and earlier:
  67         _BSD_SOURCE || _SVID_SOURCE
  68 .SH DESCRIPTION
  69 These routines are used to access the filesystem description file
  70 .I /etc/fstab
  71 and the mounted filesystem description file
  72 .IR /etc/mtab .
  73 .PP
  74 The
  75 .BR setmntent ()
  76 function opens the filesystem description file
  77 .I filename
  78 and returns a file pointer which can be used by
  79 .BR getmntent ().
  80 The argument
  81 .I type
  82 is the type of access
  83 required and can take the same values as the
  84 .I mode
  85 argument of
  86 .BR fopen (3).
  87 .PP
  88 The
  89 .BR getmntent ()
  90 function reads the next line of the filesystem
  91 description file from
  92 .I stream
  93 and returns a pointer to a structure
  94 containing the broken out fields from a line in the file.
  95 The pointer
  96 points to a static area of memory which is overwritten by subsequent
  97 calls to
  98 .BR getmntent ().
  99 .PP
 100 The
 101 .BR addmntent ()
 102 function adds the
 103 .I mntent
 104 structure
 105 .I mnt
 106 to
 107 the end of the open
 108 .IR stream .
 109 .PP
 110 The
 111 .BR endmntent ()
 112 function closes the
 113 .IR stream
 114 associated with the filesystem description file.
 115 .PP
 116 The
 117 .BR hasmntopt ()
 118 function scans the
 119 .I mnt_opts
 120 field (see below)
 121 of the
 122 .I mntent
 123 structure
 124 .I mnt
 125 for a substring that matches
 126 .IR opt .
 127 See
 128 .I <mntent.h>
 129 and
 130 .BR mount (8)
 131 for valid mount options.
 132 .PP
 133 The reentrant
 134 .BR getmntent_r ()
 135 function is similar to
 136 .BR getmntent (),
 137 but stores the
 138 .IR "struct mount"
 139 in the provided
 140 .I *mntbuf
 141 and stores the strings pointed to by the entries in that struct
 142 in the provided array
 143 .I buf
 144 of size
 145 .IR buflen .
 146 .PP
 147 The
 148 .I mntent
 149 structure is defined in
 150 .I <mntent.h>
 151 as follows:
 152 .PP
 153 .in +4n
 154 .EX
 155 struct mntent {
 156     char *mnt_fsname;   /* name of mounted filesystem */
 157     char *mnt_dir;      /* filesystem path prefix */
 158     char *mnt_type;     /* mount type (see mntent.h) */
 159     char *mnt_opts;     /* mount options (see mntent.h) */
 160     int   mnt_freq;     /* dump frequency in days */
 161     int   mnt_passno;   /* pass number on parallel fsck */
 162 };
 163 .EE
 164 .in
 165 .PP
 166 Since fields in the mtab and fstab files are separated by whitespace,
 167 octal escapes are used to represent the characters space (\e040),
 168 tab (\e011), newline (\e012), and backslash (\e\e) in those files
 169 when they occur in one of the four strings in a
 170 .I mntent
 171 structure.
 172 The routines
 173 .BR addmntent ()
 174 and
 175 .BR getmntent ()
 176 will convert
 177 from string representation to escaped representation and back.
 178 When converting from escaped representation, the sequence \e134 is
 179 also converted to a backslash.
 180 .SH RETURN VALUE
 181 The
 182 .BR getmntent ()
 183 and
 184 .BR getmntent_r ()
 185 functions return
 186 a pointer to the
 187 .I mntent
 188 structure or NULL on failure.
 189 .PP
 190 The
 191 .BR addmntent ()
 192 function returns 0 on success and 1 on failure.
 193 .PP
 194 The
 195 .BR endmntent ()
 196 function always returns 1.
 197 .PP
 198 The
 199 .BR hasmntopt ()
 200 function returns the address of the substring if
 201 a match is found and NULL otherwise.
 202 .SH FILES
 203 .TP
 204 .I /etc/fstab
 205 filesystem description file
 206 .TP
 207 .I /etc/mtab
 208 mounted filesystem description file
 209 .fi
 210 .SH ATTRIBUTES
 211 For an explanation of the terms used in this section, see
 212 .BR attributes (7).
 213 .ad l
 214 .TS
 215 allbox;
 216 lbw13 lb lbw31
 217 l l l.
 218 Interface       Attribute       Value
 219 T{
 220 .BR setmntent (),
 221 .BR endmntent (),
 222 .BR hasmntopt ()
 223 T}      Thread safety   MT-Safe
 224 T{
 225 .BR getmntent ()
 226 T}      Thread safety   MT-Unsafe race:mntentbuf locale
 227 T{
 228 .BR addmntent ()
 229 T}      Thread safety   MT-Safe race:stream locale
 230 T{
 231 .BR getmntent_r ()
 232 T}      Thread safety   MT-Safe locale
 233 .TE
 234 .ad
 235 .SH CONFORMING TO
 236 The nonreentrant functions are from SunOS 4.1.3.
 237 A routine
 238 .BR getmntent_r ()
 239 was introduced in HP-UX 10, but it returns an int.
 240 The prototype shown above is glibc-only.
 241 .SH NOTES
 242 System V also has a
 243 .BR getmntent ()
 244 function but the calling sequence
 245 differs, and the returned structure is different.
 246 Under System V
 247 .I /etc/mnttab
 248 is used.
 249 4.4BSD and Digital UNIX have a routine
 250 .BR getmntinfo (),
 251 a wrapper around the system call
 252 .BR getfsstat ().
 253 .SH SEE ALSO
 254 .BR fopen (3),
 255 .BR fstab (5),
 256 .BR mount (8)