The egrep command, also known as grep -E, is a Linux command-line utility used for pattern matching and searching within text files. It is part of the grep family of commands that are designed to search for lines in text files that match a specified pattern or regular expression. The egrep command specifically enables extended regular expression support, allowing for more complex pattern matching than the basic grep command.

Here's a basic overview of how to use the egrep command:
egrep [OPTIONS] PATTERN [FILES] .


Some common options used with egrep include:

• -i: Perform a case-insensitive search.
• -v: Invert the match, showing lines that do not match the pattern.
• -r or -R: Recursively search directories for files containing the pattern.
• -l: List only the names of files containing the pattern.
• -c: Display a count of matching lines for each file.
• -w: Match whole words only.
• -n: Show line numbers along with matching lines.