Linux in a Nutshell, Third Edition

Examples of Searching

When used with grep or egrep, regular expressions normally are surrounded by quotes to avoid interpretation by the shell. (If the pattern contains a $, you must use single quotes, as in '$200', or escape the $, as in "\$200“.) When used with ed, vi, sed, and awk, regular expressions usually are surrounded by / (although any delimiter works). Here are some sample patterns:

Pattern	What does it match?
bag	The string bag.
^bag	“bag” at beginning of line or string.
bag$	“bag” at end of line or string.
^bag$	“bag” as the only text on line.
[Bb]ag	“Bag” or “bag.”
b[aeiou]g	Second character is a vowel.
b[^aeiou]g	Second character is not a vowel.
b.g	Second character is any character except newline.
^...$	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, grep or 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.
[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 alphanumeric sequence.

egrep or awk 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
80[23]?86	8086, 80286, or 80386