Linux in a Nutshell, Fifth Edition

Examples of Searching | 701

Pattern

Matching

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In ed, ex, vi, and sed, the metacharacters in the following table are valid only in a

replacement pattern.

Examples of Searching

When used with grep or egrep, regular expressions should be surrounded by

quotes. (If the pattern contains a $, you must use single quotes; e.g., 'pattern'.)

When used with ed, ex, sed, and awk, regular expressions are usually surrounded

by /, although (except for awk) any delimiter works. The following tables show

some sample patterns.

Symbol ex vi sed ed Action

\ ••••Escape following character.

\n ••••Text matching pattern stored in \( \).

& ••••Text matching search pattern.

~ • • Reuse previous replacement pattern.

% • Reuse previous replacement pattern.

\u \U • • Change character(s) to uppercase.

\l \L • • Change character(s) to lowercase.

\e • • Turn off previous \u or \l.

\E • • Turn off previous \U or \L.

Pattern What does it match?

bag The string bag.

^bag bag at the beginning of the line.

bag$ bag at the end of the line.

^bag$ bag as the only word on the line.

[Bb]ag Bag or bag.

b[aeiou]g Second letter is a vowel.

b[^aeiou]g Second letter is a consonant (or uppercase or symbol).

b.g Second letter is any character.

^...$ Any line containing exactly three characters.

^\. Any line that begins with a dot.

^\.[a-z][a-z] Same, ...