The egrep command is yet another version of
one that extends
A plus sign (
+) following a regular expression matches one or more
occurrences of the regular expression; a question mark (
matches zero or one occurrences.
In addition, regular expressions can be nested within parentheses:
egrep "Lab(oratorie)?s" name.listAT&T Bell Laboratories AT&T Bell Labs Symtel Labs of Chicago
Parentheses surround a second regular expression and
? modifies this
The nesting helps to eliminate unwanted matches; for instance, the
word Labors or oratories would not be matched.
egrep "stdscr|curscr" ch03into the stdscr, a character array. When stdscr is refreshed, the stdscr is refreshed. curscr. initscr() creates two windows: stdscr and curscr.
Remember to put the expression inside quotation marks to protect the vertical bar from being interpreted by the shell as a pipe symbol. Look at the next example:
egrep "Alcuin (User|Programmer)('s)? Guide" docguideAlcuin Progammer's Guide is a thorough refer to the Alcuin User Guide Alcuin User's Guide introduces new users to
You can see the flexibility that egrep's syntax can give you,
Programmer and matching them whether or not they had
has another example and explanation of egrep.
Both egrep andcan read search patterns from a file using the . The utility makes a file full of complicated expressions for matching dates.
- from UNIX Text Processing, Hayden Books, 1987, Chapter 11