Linux in a Nutshell, 6th Edition

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 gawk, regular expressions are usually surrounded by /, although (except for gawk) any delimiter works. The following tables show some sample 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 gawk only.
[[:upper:]]+	Same as previous, egrep or gawk.
[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 POSIX character class.
egrep or gawk pattern	What does it match?
[567]	One of the numbers 5, 6, or 7.
five|six|seven	One of the words five, six, or seven ...