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Chapter 20. Pattern Matching > Examples of Searching

20.4. 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.

20.4.1. General 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; 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.
[^0-9A-Za-z] Any symbol or space (not a letter or a number).
[^[:alnum:]] Same, using POSIX character class.



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