Tool Building
Diomidis Spinellis
Department of Management Science and Technology
Athens University of Economics and Business
Athens, Greece
dds@aueb.gr
Implementation Options
- The Unix shell and tools (sed, awk, grep)
- Scripting language (Groovy, Perl, Python, Ruby)
- Visual Basic
- C, C++, Java
Choosing an Implementation
- A filtering pipeline (e.g. CVS logs): the Unix shell
- Record processing: awk
- Simple line-oriented string processing: sed
- Combination of tasks: scripting language
- Web front end: PHP, SWILL, GWT, Ruby on Rails
- Tight integration with Microsoft products: Visual Basic
- Extreme performance requirements: C, C++, Java
A Simple Grep Program in Java ...
/*
* Globally match regular expression and print
* Modelled after the Unix command with the same name
* D. Spinellis
*/
import java.util.regex.*;
import java.io.*;
class Grep {
public static void main(String args[]) {
if (args.length != 2) {
System.err.println("Usage: Grep pattern file");
System.exit(1);
}
Pattern cre = null; // Compiled RE
try {
cre = Pattern.compile(args[0]);
} catch (PatternSyntaxException e) {
System.err.println("Invalid RE syntax: " + e.getDescription());
System.exit(1);
}
BufferedReader in = null;
try {
in = new BufferedReader(new InputStreamReader(
new FileInputStream(args[1])));
} catch (FileNotFoundException e) {
System.err.println("Unable to open file " +
args[1] + ": " + e.getMessage());
System.exit(1);
}
try {
String s;
while ((s = in.readLine()) != null) {
Matcher m = cre.matcher(s);
if (m.find())
System.out.println(s);
}
} catch (Exception e) {
System.err.println("Error reading line: " + e.getMessage());
System.exit(1);
}
}
}
... And its Equivalent in Perl
#!/usr/bin/perl -n
BEGIN {$pat = shift;}
print if (/$pat/);
Advice
- Exploit the capabilities of modern rapid-prototyping languages.
- Start with a simple design, gradually improving it as needed.
- Use heuristics that exploit the lexical structure of the code.
- Tolerate some output noise or silence
- Use other tools to preprocess your input or postprocess your output.
Example: Signature Survey
Last change: Sunday, December 6, 2009 7:40 pm