Grep command

[achuth]

Sir,
Consider the following file content

This line contains the number 113. # Match.
This line contains the number 13. # No match.
This line contains the number 133. # No match.
This line contains the number 1133. # Match.
This line contains the number 113312. # Match.
This line contains the number 1112. # No match.
This line contains the number 113312312. # Match.
This line contains no numbers at all. # No match.


Now consider the following command:
$ grep "1133*" filename

The output is
This line contains the number 113. # Match.
This line contains the number 1133. # Match.
This line contains the number 113312. # Match.
This line contains the number 113312312. # Match.

I don't understand why the first line is displayed eventhough there is no "1133".
Why is it so?

[adityamagadi]

it is because you are using * in your grep command

[Bachstelze]

1133* means 113 followed by any number of occurrences of 3, including zero.

man 7 regex

[achuth]

Is this the same for UNIX OS?

[Arndt]

Is this the same for UNIX OS?

The same as what?

[Idyll]

Yes, it works the same way in UNIX System V and Solaris 2.0. I just verified in my "UNIX in a Nustshell" book.

The symbol * "matches zero or more preceding" pattern or character specified.