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(gawk.info)Internal File Description

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Using `chdir' and `stat'
........................

   This minor node shows how to use the new functions at the `awk'
level once they've been integrated into the running `gawk' interpreter.
Using `chdir' is very straightforward. It takes one argument, the new
directory to change to:

     ...
     newdir = "/home/arnold/funstuff"
     ret = chdir(newdir)
     if (ret < 0) {
         printf("could not change to %s: %s\n",
                        newdir, ERRNO) > "/dev/stderr"
         exit 1
     }
     ...

   The return value is negative if the `chdir' failed, and `ERRNO'
(Note: Built-in Variables) is set to a string indicating the error.

   Using `stat' is a bit more complicated.  The C `stat' function fills
in a structure that has a fair amount of information.  The right way to
model this in `awk' is to fill in an associative array with the
appropriate information:

     file = "/home/arnold/.profile"
     fdata[1] = "x"    # force `fdata' to be an array
     ret = stat(file, fdata)
     if (ret < 0) {
         printf("could not stat %s: %s\n",
                  file, ERRNO) > "/dev/stderr"
         exit 1
     }
     printf("size of %s is %d bytes\n", file, fdata["size"])

   The `stat' function always clears the data array, even if the `stat'
fails.  It fills in the following elements:

`"name"'
     The name of the file that was `stat''ed.

`"dev"'
`"ino"'
     The file's device and inode numbers, respectively.

`"mode"'
     The file's mode, as a numeric value. This includes both the file's
     type and its permissions.

`"nlink"'
     The number of hard links (directory entries) the file has.

`"uid"'
`"gid"'
     The numeric user and group ID numbers of the file's owner.

`"size"'
     The size in bytes of the file.

`"blocks"'
     The number of disk blocks the file actually occupies. This may not
     be a function of the file's size if the file has holes.

`"atime"'
`"mtime"'
`"ctime"'
     The file's last access, modification, and inode update times,
     respectively.  These are numeric timestamps, suitable for
     formatting with `strftime' (Note: Built-in Functions.).

`"pmode"'
     The file's "printable mode."  This is a string representation of
     the file's type and permissions, such as what is produced by `ls
     -l'--for example, `"drwxr-xr-x"'.

`"type"'
     A printable string representation of the file's type.  The value
     is one of the following:

    `"blockdev"'
    `"chardev"'
          The file is a block or character device ("special file").

    `"directory"'
          The file is a directory.

    `"fifo"'
          The file is a named-pipe (also known as a FIFO).

    `"file"'
          The file is just a regular file.

    `"socket"'
          The file is an `AF_UNIX' ("Unix domain") socket in the
          filesystem.

    `"symlink"'
          The file is a symbolic link.

   Several additional elements may be present depending upon the
operating system and the type of the file.  You can test for them in
your `awk' program by using the `in' operator (Note: Referring to an
Array Element.):

`"blksize"'
     The preferred block size for I/O to the file. This field is not
     present on all POSIX-like systems in the C `stat' structure.

`"linkval"'
     If the file is a symbolic link, this element is the name of the
     file the link points to (i.e., the value of the link).

`"rdev"'
`"major"'
`"minor"'
     If the file is a block or character device file, then these values
     represent the numeric device number and the major and minor
     components of that number, respectively.