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 opendir ,
  40 .Nm readdir ,
  41 .Nm readdir_r ,
  42 .Nm telldir ,
  43 .Nm seekdir ,
  44 .Nm rewinddir ,
  45 .Nm closedir ,
  46 .Nm dirfd
  47 .Nd directory operations
  48 .Sh LIBRARY
  49 .Lb libc
  50 .Sh SYNOPSIS
  51 .In sys/types.h
  52 .In dirent.h
  53 .Ft DIR *
  54 .Fn opendir "const char *filename"
  55 .Ft struct dirent *
  56 .Fn readdir "DIR *dirp"
  57 .Ft int
  58 .Fn readdir_r "DIR *dirp" "struct dirent *entry" "struct dirent **result"
  59 .Ft long
  60 .Fn telldir "DIR *dirp"
  61 .Ft void
  62 .Fn seekdir "DIR *dirp" "long  loc"
  63 .Ft void
  64 .Fn rewinddir "DIR *dirp"
  65 .Ft int
  66 .Fn closedir "DIR *dirp"
  67 .Ft int
  68 .Fn dirfd "DIR *dirp"
  69 .Sh DESCRIPTION
  70 The
  71 .Fn opendir
  72 function
  73 opens the directory named by
  74 .Fa filename ,
  75 associates a
  76 .Em directory stream
  77 with it
  78 and
  79 returns a pointer to be used to identify the
  80 .Em directory stream
  81 in subsequent operations.  The pointer
  82 .Dv NULL
  83 is returned if
  84 .Fa filename
  85 cannot be accessed, or if it cannot
  86 .Xr malloc 3
  87 enough memory to hold the whole thing.
  88 .Pp
  89 The
  90 .Fn readdir
  91 function
  92 returns a pointer to the next directory entry.  It returns
  93 .Dv NULL
  94 upon reaching the end of the directory or detecting an invalid
  95 .Fn seekdir
  96 operation.
  97 .Pp
  98 .Fn readdir_r
  99 provides the same functionality as
 100 .Fn readdir ,
 101 but the caller must provide a directory
 102 .Fa entry
 103 buffer to store the results in.  If the read succeeds,
 104 .Fa result
 105 is pointed at the
 106 .Fa entry ;
 107 upon reaching the end of the directory
 108 .Fa result
 109 is set to
 110 .Dv NULL .
 111 .Fn readdir_r
 112 returns 0 on success or an error number to indicate failure.
 113 .Pp
 114 The
 115 .Fn telldir
 116 function
 117 returns the current location associated with the named
 118 .Em directory stream .
 119 Values returned by
 120 .Fn telldir
 121 are good only for the lifetime of the
 122 .Dv DIR
 123 pointer,
 124 .Fa dirp ,
 125 from which they are derived.  If the directory is closed and then
 126 reopened, prior values returned by
 127 .Fn telldir
 128 will no longer be valid.
 129 .Pp
 130 The
 131 .Fn seekdir
 132 function
 133 sets the position of the next
 134 .Fn readdir
 135 operation on the
 136 .Em directory stream .
 137 The new position reverts to the one associated with the
 138 .Em directory stream
 139 when the
 140 .Fn telldir
 141 operation was performed.
 142 .Pp
 143 The
 144 .Fn rewinddir
 145 function
 146 resets the position of the named
 147 .Em directory stream
 148 to the beginning of the directory.
 149 .Pp
 150 The
 151 .Fn closedir
 152 function
 153 closes the named
 154 .Em directory stream
 155 and frees the structure associated with the
 156 .Fa dirp
 157 pointer,
 158 returning 0 on success.
 159 On failure, \-1 is returned and the global variable
 160 .Va errno
 161 is set to indicate the error.
 162 .Pp
 163 The
 164 .Fn dirfd
 165 function
 166 returns the integer file descriptor associated with the named
 167 .Em directory stream ,
 168 see
 169 .Xr open 2 .
 170 .Pp
 171 Sample code which searches a directory for entry ``name'' is:
 172 .Bd -literal -offset indent
 173 len = strlen(name);
 174 dirp = opendir(".");
 175 while ((dp = readdir(dirp)) != NULL)
 176         if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
 177                 (void)closedir(dirp);
 178                 return FOUND;
 179         }
 180 (void)closedir(dirp);
 181 return NOT_FOUND;
 182 .Ed
 183 .Sh SEE ALSO
 184 .Xr close 2 ,
 185 .Xr lseek 2 ,
 186 .Xr open 2 ,
 187 .Xr read 2 ,
 188 .Xr dir 5
 189 .Sh HISTORY
 190 The
 191 .Fn opendir ,
 192 .Fn readdir ,
 193 .Fn telldir ,
 194 .Fn seekdir ,
 195 .Fn rewinddir ,
 196 .Fn closedir ,
 197 and
 198 .Fn dirfd
 199 functions appeared in
 200 .Bx 4.2 .