Shell is a program, which interprets user commands. The commands are either directly entered by the user or read from a file called the shell script.

The first time I played with Zenity, I recognized several potential uses for it. While I'm pretty comfortable with interacting with computers with a command line interface, I know many people are not. Zenity creates GUI widgets from a simple command line and can be used from any shell script.

You can copy command line output to X Windows clipboard directly using xclip command. You can read from standard input (keyboard), or from one or more files, and makes the data available as an X selection for pasting into any X applications such as gedit, OpenOffice or Firefox / email client.

There are times when you will want to trim some information from the output of a command. This may be because you want to feed that output into another command. Whatever the reason for wanting to manipulate the output, awk is one of many tools available in GNU/Linux to perform this task.

The output of most GNU command line tools is normally sent to the terminal (ie – standard output). There are times when you would like to have the output saved as a file. Now, you could copy the text from the terminal and paste it into a text editor and save it, but there’s a better way...

One of the most powerful features of the Linux command line interface, (and other shells that conform to the POSIX standard) is the ability to pipeline output from one command as the input to another. This is done using the vertical bar or pipe character [ | ].

Command substitution takes the output of one Linux command and makes it an argument in another command.

The Linux tee command is a way to write the standard output to a file. This is a little different from redirecting output to a file. In this case, the output is still send to standard out, but an additional copy is sent to create your text file.

There are a number of ways you can use pipes in the Bash Shell to send the output of one command into the input in another command.