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17.7.6 Reading Directories
--------------------------

The 'readdir' extension adds an input parser for directories.  The usage
is as follows:

     @load "readdir"

   When this extension is in use, instead of skipping directories named
on the command line (or with 'getline'), they are read, with each entry
returned as a record.

   The record consists of three fields.  The first two are the inode
number and the file name, separated by a forward slash character.  On
systems where the directory entry contains the file type, the record has
a third field (also separated by a slash), which is a single letter
indicating the type of the file.  The letters and their corresponding
file types are shown in *note Table 17.4: table-readdir-file-types.


Letter  File type
--------------------------------------------------------------------------
'b'     Block device
'c'     Character device
'd'     Directory
'f'     Regular file
'l'     Symbolic link
'p'     Named pipe (FIFO)
's'     Socket
'u'     Anything else (unknown)

Table 17.4: File types returned by the 'readdir' extension

   On systems without the file type information, the third field is
always 'u'.

     NOTE: On GNU/Linux systems, there are filesystems that don't
     support the 'd_type' entry (see the readdir(3) manual page), and so
     the file type is always 'u'.  You can use the 'filefuncs' extension
     to call 'stat()' in order to get correct type information.

   By default, if a directory cannot be opened (due to permission
problems, for example), 'gawk' will exit.  As with regular files, this
situation can be handled using a 'BEGINFILE' rule that checks 'ERRNO'
and prints an error or otherwise handles the problem.

   Here is an example:

     @load "readdir"
     ...
     BEGIN { FS = "/" }
     { print "file name is", $2 }