Awesome print function | skybert.net

Awesome print function


This little gem here will print the method and line number from which the printing statement is made, giving you as developer or operator much more valuable debugging output.

The gem is:

print() {
  echo $(basename $0):${BASH_LINENO[0]}:${FUNCNAME[1]}"()" "$*"
}

It starts of by outputting the script that is executed using the familiar $(basename $0) construct. Then on to the exciting part: The first element of the BASH_LINENO array will contain the line number and the second element in the FUNCNAME array will hold the calling method. The $* simply outputs all the arguments that are passed to the print() method.

Here's a demo application which checks out some source, compoiles it and starts a dev server, providing the user with information as it goes along:

#! /usr/bin/env bash

print() {
  echo $(basename $0):${BASH_LINENO[0]}:${FUNCNAME[1]}"()" "$*"
}

checkout_source() {
  print "Checking out $1 ..."
}

compile_source() {
  print "Compiling source in $1 ..."
}

start_dev_server() {
  print "Starting dev server on port $1 ..."
}

main() {
  checkout_source https://github.com/eclipse/che.git
  compile_source che
  start_dev_server 8080
}

main "$@"

Running this command will give you both debug messges and trace of exactly from which file, line number and method they are being issued:

$ callee-test.sh
callee-test.sh:17:checkout_source() Checking out https://github.com/eclipse/che.git ...
callee-test.sh:21:compile_source() Compiling source in che ...
callee-test.sh:25:start_dev_server() Starting dev server on port 8080 ...

If you're running this in something like the Emacs compile buffer, you can even click on the logging statements to jump to the source code where they are issued.

Pretty cool, eh?

What about Java?

Interestingly, Java also has a way to do this. AFAIK, log4j and other logging frameworks don't use it, but you can:

private static void print(final String pMessage) {
  System.out.println(
      Thread.currentThread().getStackTrace()[2].getFileName() + ":" +
      Thread.currentThread().getStackTrace()[2].getLineNumber() + ":" +
      Thread.currentThread().getStackTrace()[2].getMethodName() + "() " +
      pMessage);
}

gmail torstein.k.johansen @ gmail ~ twitter @torsteinkrause ~