Regular Expressions in the Real World : egrep

The program "egrep" is an acronym for "extended global regular expressions print" and may be used to search for a string or a more complex pattern in a file. Regular expressions provide a convenient, compact way of expressing patterns. The internal workings of egrep are based on finite automata.

The command format is: egrep ‘regexp’ file
where file is a file name and regexp is a regular expression whose format will be described shortly. Egrep returns all strings in the file which match the regular expression.

The format of a regular expression in egrep is as follows:

Try the following examples:

egrep ‘depend’ /usr/dict/words
egrep ‘^y.*y$’ /usr/dict/words
egrep ‘y.*y’ /usr/dict/words
egrep ‘^rec(ei|ie)ve$’ /usr/dict/words
egrep ‘^s..u.t..e$’ /usr/dict/words
egrep ‘(^| )the +the( |$)’ ~jillz/cs250/testfile