DIRECTORY(3)                   Library Routines                   DIRECTORY(3)




NAME

       opendir, readdir, telldir, seekdir, rewinddir, closedir, dirfd - direc-
       tory operations


SYNOPSIS

       #include <sys/types.h>
       #include <dirent.h>

       DIR *opendir (const char *filename);
       struct dirent *readdir (DIR *dirp);
       long telldir (const DIR *dirp);
       void seekdir (DIR *dirp, long loc);
       void rewinddir (DIR *dirp);
       int closedir (DIR *dirp);
       int dirfd (DIR *dirp);


DESCRIPTION

       The opendir function opens the directory named by filename,  associates
       a directory stream with it and returns a pointer to be used to identify
       the directory stream in subsequent operations.   The  pointer  NULL  is
       returned  if  filename  cannot  be  accessed, or if it cannot malloc(3)
       enough memory to hold the whole thing.

       The readdir function returns a pointer to the next directory entry.  It
       returns  NULL  upon  reaching  the end of the directory or detecting an
       invalid seekdir operation.  The  GNO  implementation  will  not  return
       entries  for  either the current directory (.)  or the parent directory
       (..).  Directory entries are defined  by  the  following  structure  in
       <sys/dirent.h>:

       struct dirent {
            unsigned long  d_fileno; /* file number of entry */
            unsigned short d_reclen; /* length of this record */
            unsigned char  d_type;        /* file type (non-IIgs) */
            unsigned char  d_namlen; /* length of string in d_name */
            char      d_name[256];   /* name must be no longer than this */
       }

       The  value of d_fileno is, on most architectures, the inode of the cur-
       rent file.  Since inodes are not used on any current GS/OS  FSTs,  this
       number corresponds to the offset of this file in the current directory.
       d_reclen is the length of the entire struct dirent.  The d_type  member
       is currently set to DT_DIR for directories, DT_REG otherwise.  d_namlen
       is the length of the file name contained in d_name.

       Subsequent calls to readdir will  overwrite  previous  results  in  the
       struct  dirent;  if  the results must be saved then they should be mem-
       cpy?d to a user-defined buffer.

       The telldir function returns the current location associated  with  the
       named  directory stream.  The result of a telldir on a stream which has
       just been opened is undefined.

       The seekdir function sets the position of the next readdir operation on
       the  directory  stream.  The new position reverts to the one associated
       with the directory stream when the  telldir  operation  was  performed.
       Values  returned  by  telldir are good only for the lifetime of the DIR
       pointer, (dirp) from which they  are  derived.   If  the  directory  is
       closed  and  then reopened, the telldir value may be invalidated due to
       undetected directory compaction.

       The rewinddir function resets  the  position  of  the  named  directory
       stream to the beginning of the directory.

       The  closedir  function closes the named directory stream and frees the
       structure associated with the dirp pointer, returning 0 on success.  On
       failure,  -1  is returned and the global variable errno is set to indi-
       cate the error.

       The dirfd function returns the integer file descriptor associated  with
       the named directory stream, see open(2).


EXAMPLE

       Sample  code  which  searches a directory for entry ''name'' in a case-
       sensitive manner is:

       len = strlen(name);
       dirp = opendir(".");
       while ((dp = readdir(dirp)) != NULL)
            if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
                 (void)closedir(dirp);
                 return FOUND;
            }
       (void)closedir(dirp);
       return NOT_FOUND;


BUGS

       The GNO implementation of seekdir and rewinddir rely on the GS/OS  call
       GetDirEntryGS.   It  is  thus  possible for these routines to fail.  If
       they do, the error will not be detected until a subsequent  readdir  is
       performed.


SEE ALSO

       open(2), close(2), read(2), lseek(2), dir(5)


HISTORY

       The  opendir, readdir, telldir, seekdir, rewinddir, closedir, and dirfd
       functions appeared in BSD 4.2.



GNO                             29 January 1997                   DIRECTORY(3)

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