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 example patterns.

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, followed by two lowercase letters (e.g., troff requests).

^\.[a-z]\{2\}

Same as previous, ed, grep, and sed only.

^[^.]

Any line that doesn’t begin with a dot.

bugs*

bug, bugs, bugss, etc.

"word"

A word in quotes.

"*word"*

A word, with or without quotes.

[A-Z][A-Z]*

One or more uppercase letters.

[A-Z]+

Same; egrep or awk only.

[[:upper:]]+

Same as previous, POSIX egrep or awk.

[A-Z].*

An uppercase letter, followed by zero or more characters.

[A-Z]*

Zero or more uppercase letters.

[a-zA-Z]

Any letter, either lower- or uppercase.

[^0-9A-Za-z]

Any symbol or space (not a letter or a number).

[^[:alnum:]]

Same, using ...

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