Linux in a Nutshell, Fourth Edition

Examples of Searching

When used with grep or egrep, regular expressions are normally 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 gawk, regular expressions are usually surrounded by / (although any delimiter works). Here are some sample patterns:

Pattern	Matches
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"	The string “word” in quotes
"*word"*	The string “word”, with or without quotes
[A-Z][A-Z]*	One or more uppercase letters
[A-Z]+	Same (egrep or gawk 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 gawk pattern	Matches
[567]	One of the numbers 5, 6, or 7
five|six|seven ...