Regular Expressions: Matching a Character with a Character Set

The simplest character set is a single character. The regular expression the contains three character sets: t, h, and e. It will match any line that contains the string the, including the word other. To prevent this, put spaces (·) before and after the pattern: ·the·.

You can combine the string with an anchor. The pattern ^From:· will match the lines of a mail message (Section 1.21) that identify the sender. Use this pattern with grep to print every address in your incoming mailbox. [If your system doesn't define the environment variable MAIL, try /var/spool/mail/$USER or possibly /usr/spool/mail/$USER. — SJC]

$USER Section 35.5

% grep '^From: ' $MAIL

Some characters have a special meaning in regular expressions. If you want to search for such a character as itself, escape it with a backslash (\).

— BB