gen/directory.3

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  28 .\"     @(#)directory.3 8.1 (Berkeley) 6/4/93
  29 .\" $FreeBSD: src/lib/libc/gen/directory.3,v 1.12 2001/10/01 16:08:50 ru Exp $
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  31 .Dd June 4, 1993
  32 .Dt DIRECTORY 3
  33 .Os
  34 .Sh NAME
  35 .Nm closedir ,
  36 .Nm dirfd ,
  37 .Nm opendir ,
  38 .Nm readdir ,
  39 .Nm readdir_r ,
  40 .Nm rewinddir ,
  41 .Nm seekdir ,
  42 .Nm telldir
  43 .Nd directory operations
  44 .Sh LIBRARY
  45 .Lb libc
  46 .Sh SYNOPSIS
  47 .In dirent.h
  48 .Ft int
  49 .Fn closedir "DIR *dirp"
  50 .Ft int
  51 .Fn dirfd "DIR *dirp"
  52 .Ft DIR *
  53 .Fn opendir "const char *dirname"
  54 .Ft struct dirent *
  55 .Fn readdir "DIR *dirp"
  56 .Ft int
  57 .Fn readdir_r "DIR *restrict dirp" "struct dirent *restrict entry" \
  58     "struct dirent **restrict result"
  59 .Ft void
  60 .Fn rewinddir "DIR *dirp"
  61 .Ft void
  62 .Fn seekdir "DIR *dirp" "long loc"
  63 .Ft long
  64 .Fn telldir "DIR *dirp"
  65 .Sh DESCRIPTION
  66 The
  67 .Fn opendir
  68 function
  69 opens the directory named by
  70 .Fa dirname ,
  71 associates a
  72 .Em directory stream
  73 with it,
  74 and returns a pointer to be used to identify the
  75 .Em directory stream
  76 in subsequent operations.
  77 In the event of an error, NULL
  78 is returned and
  79 .Va errno
  80 will be set to reflect if
  81 .Fa dirname
  82 cannot be accessed or if it cannot
  83 .Xr malloc 3
  84 enough memory to hold the whole thing.
  85 .Pp
  86 The
  87 .Fn readdir
  88 function
  89 returns a pointer to the next directory entry.
  90 It returns
  91 .Dv NULL
  92 upon reaching the end of the directory or on error.
  93 In the event of an error,
  94 .Va errno
  95 will be set to any of the values documented for the
  96 .Xr getdirentries 2
  97 system call.
  98 .Pp
  99 The
 100 .Fn readdir_r
 101 function
 102 provides the same functionality as
 103 .Fn readdir ,
 104 but the caller must provide a directory
 105 .Fa entry
 106 buffer to store the results in.
 107 If the read succeeds,
 108 .Fa result
 109 is pointed at the
 110 .Fa entry ;
 111 upon reaching the end of the directory,
 112 .Fa result
 113 is set to
 114 .Dv NULL .
 115 The
 116 .Fn readdir_r
 117 function
 118 returns 0 on success or an error number to indicate failure.
 119 .Pp
 120 The
 121 .Fn telldir
 122 function
 123 returns the current location associated with the named
 124 .Em directory stream .
 125 Values returned by
 126 .Fn telldir
 127 are good only for the lifetime of the
 128 .Dv DIR
 129 pointer (e.g.,
 130 .Fa dirp )
 131 from which they are derived.
 132 If the directory is closed and then
 133 reopened, prior values returned by
 134 .Fn telldir
 135 will no longer be valid.
 136 .Pp
 137 The
 138 .Fn seekdir
 139 function
 140 sets the position of the next
 141 .Fn readdir
 142 operation on the
 143 .Em directory stream .
 144 The new position reverts to the one associated with the
 145 .Em directory stream
 146 when the
 147 .Fn telldir
 148 operation was performed.
 149 .Pp
 150 The
 151 .Fn rewinddir
 152 function
 153 resets the position of the named
 154 .Em directory stream
 155 to the beginning of the directory.
 156 .Pp
 157 The
 158 .Fn closedir
 159 function
 160 closes the named
 161 .Em directory stream
 162 and frees the structure associated with the
 163 .Fa dirp
 164 pointer,
 165 returning 0 on success.
 166 On failure, \-1 is returned and the global variable
 167 .Va errno
 168 is set to indicate the error.
 169 .Pp
 170 The
 171 .Fn dirfd
 172 function
 173 returns the integer file descriptor associated with the named
 174 .Em directory stream
 175 on success, see
 176 .Xr open 2 .
 177 On failure, \-1 is returned and the global variable
 178 .Va errno
 179 is set to indicate the error.
 180 .Pp
 181 Sample code which searches a directory for entry ``name'' is:
 182 .Bd -literal -offset indent
 183 dirp = opendir(".");
 184 if (dirp == NULL)
 185         return (ERROR);
 186 len = strlen(name);
 187 while ((dp = readdir(dirp)) != NULL) {
 188         if (dp->d_namlen == len && strcmp(dp->d_name, name) == 0) {
 189                 (void)closedir(dirp);
 190                 return (FOUND);
 191         }
 192 }
 193 (void)closedir(dirp);
 194 return (NOT_FOUND);
 195 .Ed
 196 .Sh LEGACY SYNOPSIS
 197 .Fd #include <sys/types.h>
 198 .Fd #include <dirent.h>
 199 .Pp
 200 .In sys/types.h
 201 is necessary for these functions.
 202 .Sh SEE ALSO
 203 .Xr close 2 ,
 204 .Xr lseek 2 ,
 205 .Xr open 2 ,
 206 .Xr read 2 ,
 207 .Xr compat 5 ,
 208 .Xr dir 5
 209 .Sh HISTORY
 210 The
 211 .Fn closedir ,
 212 .Fn dirfd ,
 213 .Fn opendir ,
 214 .Fn readdir ,
 215 .Fn rewinddir ,
 216 .Fn seekdir ,
 217 and
 218 .Fn telldir
 219 functions appeared in
 220 .Bx 4.2 .