Search file(s) for lines that match an extended expression (extended grep)
egrep [ options ] “PATTERN” files …
egrep is the same as “grep -E” all other options are the same as grep
The PATTERN is a regexp. In typical usage, the regexp is quoted to prevent the shell from expanding any of the special characters as file name wildcards. Normally, “egrep” prints the lines that matched. If multiple file names are provided on the command line, each output line is preceded by the name of the file and a colon.
Print out a count of the lines that matched the pattern, instead of the lines themselves.
Be silent. No output is produced, and the exit value indicates whether or not the pattern was matched.
Invert the sense of the test. “egrep” prints the lines that do *not* match the pattern, and exits successfully if the pattern was
not matched.
Ignore case distinctions in both the pattern and the input data.
Only print the names of the files that matched, not the lines that matched.
Use PATTERN as the regexp to match. The purpose of the “-e” option is to allow patterns that start with a “-“.