Examples of Searching (Linux in a Nutshell, 4th Edition)

9.4. Examples of Searching

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

One of the words five, six, or seven

80[23]?86

8086, 80286, or 80386

compan(y|ies)

company or companies

vi pattern

Matches

\<the

Words like theater or the

the\>

Words like breathe or the

\<the\>

The word the

sed or grep pattern

Matches

0\{5,\}

Five or more zeros in a row

[0-9]\{3\}-[0-9]\{2\}-[0-9]\{4\}

Social security number (nnn-nn-nnnn)

Command	Result
*s/./(&)/**	Reproduce the entire line, but add parentheses.
*s/./mv & &.old/**	Change a wordlist (one word per line) into mv commands.
/^$/d	Delete blank lines.
:g/^$/d	Same as previous, in vi editor.
/^[·tab*]$/d**	Delete blank lines, plus lines containing spaces or tabs.
:g/^[·tab*]$/d**	Same as previous, in vi editor.
s/··*/·/g	Turn one or more spaces into one space.
:%s/··*/·/g	Same as previous, in vi editor.
:s/[0-9]/Item &:/	Turn a number into an item label (on the current line).
:s	Repeat the substitution on the first occurrence.
:&	Same as previous.
:sg	Same, but for all occurrences on the line.
:&g	Same as previous.
:%&g	Repeat the substitution globally.
:.,$s/Fortran/\U&/g	Change word to uppercase, on current line to last line.
*:%s/./\L&/**	Lowercase entire file.
:s/\<./\u&/g	Uppercase first letter of each word on current line. (Useful for titles.)
:%s/yes/No/g	Globally change a string ("yes") to another string ("No").
:%s/Yes/~/g	Globally change a different string to "No" (previous replacement).

Finally, here are some sed examples for transposing words. A simple transposition of two words might look like this:

s/die or do/do or die/        Transpose words

The real trick is to use hold buffers to transpose variable patterns. For example:

s/\([Dd]ie\) or \([Dd]o\)/\2 or\1/          Transpose using hold buffers