Programming with awk

Files and pipes

You can provide input to an awk program by putting the input data into a file, say awkdata, and then executing

   $ awk 'program' awkdata<<Return>>

If no filenames are given, awk reads its standard input; thus, a second common arrangement is to have another program pipe its output into awk. For example, grep(1) selects input lines containing a specified regular expression, but it can do so faster than awk, since this is the only thing it does. We could, therefore, invoke the pipe

   $ grep 'Asia' countries | awk '. . .'<<Return>>

grep quickly finds the lines containing Asia and passes them on to the awk program for subsequent processing.