and speed of execution, rest command line parameters remain same for all the three versions of grep and even instead of “egrep” or “fgrep”, “grep -E” or “grep -F” are recommended to be used.
specified, or if the file “-” is given,grepsearches standard input. By default,grepprints the matching lines. In addition, the variant programsegrep,fgrepandrgrepare the same asgrep-E,grep-F, andgrep-r, respectively. These variants are deprecated, but are provided for backward compatibility...
Matching Control -e PATTERN, --regexp=PATTERN User Commands Last change: GNU grep 2.14 1 User Commands GREP(1) Use PATTERN as the pattern. This can be used to specify multiple search patterns, or to protect a pattern beginning with a hyphen (-). (-e is specified by POSIX.) -f FILE...
You know that grep works on regex. But that's not the complete truth. By default, the grep command works on basic regular expression. If you want more complex search, you need to use extended regular expression. See the difference between basic and extended regex. The egrep command allows ...