gen/directory.3

   1 .\" Copyright (c) 1983, 1991, 1993
   2 .\"     The Regents of the University of California.  All rights reserved.
   3 .\"
   4 .\" Redistribution and use in source and binary forms, with or without
   5 .\" modification, are permitted provided that the following conditions
   6 .\" are met:
   7 .\" 1. Redistributions of source code must retain the above copyright
   8 .\"    notice, this list of conditions and the following disclaimer.
   9 .\" 2. Redistributions in binary form must reproduce the above copyright
  10 .\"    notice, this list of conditions and the following disclaimer in the
  11 .\"    documentation and/or other materials provided with the distribution.
  12 .\" 3. All advertising materials mentioning features or use of this software
  13 .\"    must display the following acknowledgement:
  14 .\"     This product includes software developed by the University of
  15 .\"     California, Berkeley and its contributors.
  16 .\" 4. Neither the name of the University nor the names of its contributors
  17 .\"    may be used to endorse or promote products derived from this software
  18 .\"    without specific prior written permission.
  19 .\"
  20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30 .\" SUCH DAMAGE.
  31 .\"
  32 .\"     @(#)directory.3 8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/lib/libc/gen/directory.3,v 1.12 2001/10/01 16:08:50 ru Exp $
  34 .\"
  35 .Dd June 4, 1993
  36 .Dt DIRECTORY 3
  37 .Os
  38 .Sh NAME
  39 .Nm closedir ,
  40 .Nm dirfd ,
  41 .Nm opendir ,
  42 .Nm readdir ,
  43 .Nm readdir_r ,
  44 .Nm rewinddir ,
  45 .Nm seekdir ,
  46 .Nm telldir
  47 .Nd directory operations
  48 .Sh LIBRARY
  49 .Lb libc
  50 .Sh SYNOPSIS
  51 .In dirent.h
  52 .Ft int
  53 .Fn closedir "DIR *dirp"
  54 .Ft int
  55 .Fn dirfd "DIR *dirp"
  56 .Ft DIR *
  57 .Fn opendir "const char *dirname"
  58 .Ft struct dirent *
  59 .Fn readdir "DIR *dirp"
  60 .Ft int
  61 .Fn readdir_r "DIR *restrict dirp" "struct dirent *restrict entry" \
  62     "struct dirent **restrict result"
  63 .Ft void
  64 .Fn rewinddir "DIR *dirp"
  65 .Ft void
  66 .Fn seekdir "DIR *dirp" "long  loc"
  67 .Ft long
  68 .Fn telldir "DIR *dirp"
  69 .Sh DESCRIPTION
  70 The
  71 .Fn opendir
  72 function
  73 opens the directory named by
  74 .Fa dirname ,
  75 associates a
  76 .Em directory stream
  77 with it,
  78 and returns a pointer to be used to identify the
  79 .Em directory stream
  80 in subsequent operations.  The pointer
  81 .Dv NULL
  82 is returned if
  83 .Fa dirname
  84 cannot be accessed or if it cannot
  85 .Xr malloc 3
  86 enough memory to hold the whole thing.
  87 .Pp
  88 The
  89 .Fn readdir
  90 function
  91 returns a pointer to the next directory entry.  It returns
  92 .Dv NULL
  93 upon reaching the end of the directory or detecting an invalid
  94 .Fn seekdir
  95 operation.
  96 .Pp
  97 .Fn readdir_r
  98 provides the same functionality as
  99 .Fn readdir ,
 100 but the caller must provide a directory
 101 .Fa entry
 102 buffer to store the results in.  If the read succeeds,
 103 .Fa result
 104 is pointed at the
 105 .Fa entry ;
 106 upon reaching the end of the directory,
 107 .Fa result
 108 is set to
 109 .Dv NULL .
 110 .Fn readdir_r
 111 returns 0 on success or an error number to indicate failure.
 112 .Pp
 113 The
 114 .Fn telldir
 115 function
 116 returns the current location associated with the named
 117 .Em directory stream .
 118 Values returned by
 119 .Fn telldir
 120 are good only for the lifetime of the
 121 .Dv DIR
 122 pointer (e.g.,
 123 .Fa dirp )
 124 from which they are derived.  If the directory is closed and then
 125 reopened, prior values returned by
 126 .Fn telldir
 127 will no longer be valid.
 128 .Pp
 129 The
 130 .Fn seekdir
 131 function
 132 sets the position of the next
 133 .Fn readdir
 134 operation on the
 135 .Em directory stream .
 136 The new position reverts to the one associated with the
 137 .Em directory stream
 138 when the
 139 .Fn telldir
 140 operation was performed.
 141 .Pp
 142 The
 143 .Fn rewinddir
 144 function
 145 resets the position of the named
 146 .Em directory stream
 147 to the beginning of the directory.
 148 .Pp
 149 The
 150 .Fn closedir
 151 function
 152 closes the named
 153 .Em directory stream
 154 and frees the structure associated with the
 155 .Fa dirp
 156 pointer,
 157 returning 0 on success.
 158 On failure, \-1 is returned and the global variable
 159 .Va errno
 160 is set to indicate the error.
 161 .Pp
 162 The
 163 .Fn dirfd
 164 function
 165 returns the integer file descriptor associated with the named
 166 .Em directory stream
 167 on success, see
 168 .Xr open 2 .
 169 On failure, \-1 is returned and the global variable
 170 .Va errno
 171 is set to indicate the error.
 172 .Pp
 173 Sample code which searches a directory for entry ``name'' is:
 174 .Bd -literal -offset indent
 175 len = strlen(name);
 176 dirp = opendir(".");
 177 while ((dp = readdir(dirp)) != NULL)
 178         if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
 179                 (void)closedir(dirp);
 180                 return FOUND;
 181         }
 182 (void)closedir(dirp);
 183 return NOT_FOUND;
 184 .Ed
 185 .Sh LEGACY SYNOPSIS
 186 .Fd #include <sys/types.h>
 187 .Fd #include <dirent.h>
 188 .Pp
 189 .In sys/types.h
 190 is necessary for these functions.
 191 .Sh SEE ALSO
 192 .Xr close 2 ,
 193 .Xr lseek 2 ,
 194 .Xr open 2 ,
 195 .Xr read 2 ,
 196 .Xr compat 5 ,
 197 .Xr dir 5
 198 .Sh HISTORY
 199 The
 200 .Fn closedir ,
 201 .Fn dirfd ,
 202 .Fn opendir ,
 203 .Fn readdir ,
 204 .Fn rewinddir ,
 205 .Fn seekdir ,
 206 and
 207 .Fn telldir
 208 functions appeared in
 209 .Bx 4.2 .