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AnchorsEdit

Beginning of lineEdit

A search can be constrained to find the string at the beginning of the line with the symbol ^. Example:

grep '^A' filename

Finds the string A at the beginning of lines.

End of lineEdit

A search can be constrained to find the string at the end of the line with the symbol $. Example:

grep '5$' filename

Finds the string 5 at the end of lines.

Counting empty linesEdit

The combination search string ^$ finds empty lines.

To match any single characterEdit

The meta-character . matches any single character except the end of line character.

ExampleEdit

The input file contains these lines:

one
bone
throne
clone

We search with

grep '.one' filename

The results are

bone
throne
clone

The first line doesn't match.

To match zero or more charactersEdit

The meta-character * matches zero or more occurences of the previous character.

ExampleEdit

The input file bells containes these lines

bel
bell
belll
be
bet

We search with

grep 'bel*' bells

The results are

bel
bell
belll
be
bet

ExampleEdit

The input file is as the previous example. The . is used after the * to require at least a single character.

We search with

grep 'bel*.' bells

The results are

bel
bell
belll

Contrast this with the previous example. Here, we match everything except be.

ExampleEdit

The input file is as before.

We search with

grep 'bel.*' bells

The results are

bel
bell
belll

Character listsEdit

You can use a list of characters surrounded by [ and ] which will match on any single character in the list.

ExampleEdit

The input file is lines:

This is the zero line
Here y 
Crosses x

we search with

grep [xyz] lines

The result is

This is the zero line
Here y 
Crosses x

ExampleEdit

The input file is as before.

we search with

grep [xyb] lines

The result is

Here y 
Crosses x