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Linux in a Nutshell, Fourth Edition by Aaron Weber, Stephen Figgins, Ellen Siever

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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 ...

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