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.
Note
I'll use the character
">"
to denote the prompt of the command interpreter and the
character ";" for the
end of line in following examples (second character isn't
visible in the command line).
Well, use cat to see what's inside the text file askme.txt:
>
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
For example, a regular expression find$ describes the pattern find that is at the end of line.
KP.