tr

tr is a character translation tool; it's used to map certain characters in the input stream to certain other characters in the output stream.

sed

sed is a powerful stream-oriented text editor. You can learn about sed in the following developerWorks articles:

• Sed by example, Part 1: Get to know the powerful UNIX editor
• Sed by example, Part 2: Taking further advantage of the UNIX text editor
• Sed by example, Part 3: Data crunching, sed style

awk

awk is a handy line-oriented text-processing language. To learn about awk, read the following IBM developerWorks articles:

• Awk by example, Part 1: Intro to the great language with the strange name
• Awk by example, Part 2: Records, loops, and arrays
• Awk by example, Part 3: String functions and ... checkbooks?