Billy Schmidt

Performing tasks with pipelines

1. Printing from the command line. Linux provides a program called lpr that accepts standard input and sends it to the printer. It is often used with pipes and filters. Here are a couple of examples:

   
   cat poorly_formatted_report.txt | fmt | pr | lpr
   
   cat unsorted_list_with_dupes.txt | sort | uniq | pr | lpr
   
   

   In the first example, we use cat to read the file and output it to standard output, which is piped into the standard input of fmt. fmt formats the text into neat paragraphs and outputs it to standard output, which is piped into the standard input of pr. pr splits the text neatly into pages and outputs it to standard output, which is piped into the standard input of lpr. lpr takes its standard input and sends it to the printer.

   The second example starts with an unsorted list of data with duplicate entries. First, cat sends the list into sort which sorts it and feeds it into uniq which removes any duplicates. Next prand lpr are used to paginate and print the list.
   
   

2. Viewing the contents of tar files Often you will see software distributed as a gzipped tar file. This is a traditional Unix style tape archive file (created with tar) that has been compressed with gzip. You can recognize these files by their traditional file extensions, ".tar.gz" or ".tgz". You can use the following command to view the directory of such a file on a Linux system:

   tar tzvf name_of_file.tar.gz | less
   
   

        // This code highlighting is pretty slick
        public class Demo {
        private static final String CONSTANT = "String";
        private Object o;
      /**
       * Creates a new demo.
       * @param o The object to demonstrate.
       */
      public Demo(Object o) {
        this.o = o;
        String s = CONSTANT;
        int i = 1;
      }
      public static void main(String[] args) {
        Demo demo = new Demo();
      }
    }