The Linux utility sed provides a great way to substitute text strings in a file. Using the "s" option and by listing the current string and the string to use as the new text allows sed to perform this task.

So you're not a programmer, you say? If you can string a few shell commands together, it's not much of a step from there to programming. To demonstrate that, I'll take you through the steps of writing a very simple web gallery script: one that will take your images and build a little web page to show them off.

Here's a brief example of applying a regex, drawn from the UNIX command-line utility grep, which searches for a specified pattern among the content of one or more UNIX text files. The command grep -i -E '^Bat' searches for the sequence beginning-of-line (indicated with the caret, [^]), followed immediately by upper- or lowercase letters b, a, and t (the -i option ignores case in pattern matches, so B and b are equivalent, for instance). Hence, given the file heroes.txt:

In addition to creating programming structures, you can also use the semi-colon to separate stand-alone commands that you want to execute from the same command entry. If you wanted to cd to a certain directory and then look at its contents, you could enter each command on its own line. Or, you could enter them both on the same line. This process is called command chaining.

Scripts are files that contain shell commands which may be short or can be very complex. Scripts just make it easier because you can invoke one command to run all of the commands in the script. Here instead of using 8 separate commands you can use one command to execute all of them.

Familiarity with command prompts and shell scripts is still necessary if you want to get the most from your GNU/Linux system, but the less time you spend doing that the better, right? Two powerful ways to minimize your time at the command line are shell aliases and functions.

One of the most powerful tools available to you in shell scripting is the ability to search for text strings which highlight the information you need.

This package provides a program that can be used to clean out temporary-file directories. It recursively searches the directory, refusing to chdir() across symlinks, and removes files that haven't been accessed in a user-specified amount of time. You can specify a set of files to protect from deletion with a shell pattern.

Bash / CSH shell offers command history feature. Most of you may be aware and using of UP / DOWN arrow keys to recall previous commands. History expansions introduce words from the history list into the input stream, making it easy to repeat commands, insert the arguments to a previous ommand into the current input line, or fix errors in previous commands quickly.