By Using Grep and Regular Expressions
You can put some text in the text file by using your favorable editor.
A few words of Jesus are in file askme.txt.
The program cat shows the content of a text file. It
works best for short text files. To show what's inside a text file
askme.txt, use the cat program, as
follows (I'll use the character "_" to
denote the end of line in the following examples; it isn't visible in
the command line):
> cat askme.txt_
Ask, and it shall be given you_
Seek, and ye shall find_
Knock, and it shall be opened unto you._
For every one that asketh receiveth_
And he that seeketh findeth_
And to him that knocketh it shall be opened._
To search a file for lines that have a certain pattern, use the
program grep. Finding the pattern find
in the text file askme.txt:
> grep find askme.txt_
Seek, and ye shall find_
And he that seeketh findeth_
To find all occurrences of the pattern knock (including
Knock), use the regular expression
[Kk]nock:
> grep [Kk]nock
askme.txt_
Knock, and it shall be opened unto you._
And to him that knocketh it shall be opened._
Let's use a regular expression to find lines that contains dots
(.):
> grep \. askme.txt_
Knock, and it shall be opened unto you._
And to him that knocketh it shall be opened._
Regular expression is a text pattern. You can specify a regular expression by using a special kind of language.
Metacharacters are the characters that have special
meaning in text patterns. Some metacharacters are:
. Match any single
character except newline
* Match any number of the
characters
\ Turn off the special
meaning of the following character
^ Match pattern at the
beginning of the line.
$ Match pattern at the end
of a line.
[] Match any one of the
enclosed characters
A regular expression find$ describes the pattern
find that is at the end of line.
KP.