In the previous chapter, we saw that we could make use of
sed to edit files from within our scripts. The
sed command is the Stream Editor and opens the file line by line to search or edit the file contents. Historically, this goes way back to Unix where systems may not have had enough RAM to open very large files. Using
sed was absolutely required to carry out edits. Even today, we will use
sed to make changes and display data from files with hundreds and thousands of entries. It is simpler and easier and more reliable than a human trying to do the same thing. Most importantly, as we have seen, we can use
sed in scripts to edit the files automatically, no human interaction is required.
We will start by looking at
grep and search the files for text. The
grep command is short for
Regular Expression. This introduces the power of POSIX Compliant Regular Expressions before we look at
sed. Even though we are not looking at scripting in this chapter, we will be...