Table of Contents
Table of Contents
Brackets denote a character class. Simply surrounding your class with brackets will match your input once. Supplying a + will signify that your class will be repeated one or more times.
[a] Just a, once. [a-z]+ Any lower case letter one or more times. [a-zA-Z]+ Any upper or lower case letter one or more times. [a-zA-Z0-9]+ Any upper or lowercase letters or numbers one or more times.
word This will match the word "word"
(word) Allows you to match "word" as well but placing it
in parens will allow you to reference it like
this...
(word)\1 Will match "wordword" so you could do this if you were matching html
tags
<(html)>.*</\1> Will allow you to match the <html> and it's closing tag </html>.The wildcard * means that the class will be repeated zero or more times.
The . stands for absolutely anything, once.
[a-z]*[0-9]+ Zero or more a-z characters followed by one or more numbers. .* Meaning anything at all zero or more times. .at This will match hat, cat, bat, fat, etc.
A caret ^ means match this class at the beginning of my string. The ^ must preceed your class.
A dollar sign $ means match this class at the end of my string. The $ must follow your class.
^[A-Z].* Caret means 'begins with' so... any upper case letter followed by
anything zero or more times.
.*;$ Anything ending in a semicolon.Placing a bar | in your expression will signify a logical OR.
([a-b]+|[0-1]+) One or more a-b's OR one or more 1-0's.
This regular expression will match an IP Address. It's not a valid IP Address but it looks like one, at least.
([0-9]{1,3}[.]){3}([0-9]{1,3})Curly braces signify the amount of times this class will occur. Also note that you have to wrap special character such as the period in braches [.] although you could also terminate them with a back-slash like, \:
See if you can do this yourself, using the IP Address example. Valid MAC Addresses include:
C0:FF:EE:BA:BE:EE DE:AD:BE:EF:BA:BE
sed stands for stream editor and allows you to apply regular expressions to files to make quick fixes.
[23:36]abutcher@beta:~$ echo "biscuit mix" | sed 's/biscuit/beef/'
beef mix
[23:36]abutcher@beta:~$ echo " <---- Notice the leading whitespace." | sed -r 's/^[ ]+//'
<---- Notice the leading whitespace.
abutcher@shell003:~$ echo " <---- Notice the leading whitespace." > whitespace.txt
abutcher@shell003:~$ cat whitespace.txt
<---- Notice the leading whitespace.
abutcher@shell003:~$ sed -r 's/^[ ]+//' whitespace.txt
<---- Notice the leading whitespace.
abutcher@shell003:~$ sed -ri 's/^[ ]+//' whitespace.txt
abutcher@shell003:~$ cat whitespace.txt
<---- Notice the leading whitespace.
Table of Contents
package edu.wvu.mix.abutcher;
import java.io.IOException;
import java.util.regex.Pattern;
import jline.ConsoleReader;
public class RegexTest {
public static void main(String[] args) throws IOException {
ConsoleReader reader = new ConsoleReader();
String line;
while ((line = reader.readLine("$> ")) != null) {
if (Pattern.matches(".*;$", line)) {
System.out.println("\'" + line + "\' ends in a semicolon.");
}
if (Pattern.matches("([0-9]{1,3}[.]){3}([0-9]{1,3})", line)) {
System.out.println("\'" + line + "\' looks like an IP address.");
}
if (Pattern.matches("^[A-Z].*", line) ) {
System.out.println("\'" + line + "\' begins with a capital letter.");
}
}
}
}