2.3.1. Debugging on the entire script

Jump to:

When things don't go according to plan, you need to determine what exactly causes the script to fail. Bash provides extensive debugging features. The most common is to start up the subshell with the -x option, which will run the entire script in debug mode. Traces of each command plus its arguments are printed to standard output after the commands have been expanded but before they are executed.

This is the commented-script1.sh script ran in debug mode. Note again that the added comments are not visible in the output of the script.

willy:~/scripts> bash -x script1.sh
+ clear

+ echo 'The script starts now.'
The script starts now.
+ echo 'Hi, willy!'
Hi, willy!
+ echo

+ echo 'I will now fetch you a list of connected users:'
I will now fetch you a list of connected users:
+ echo

+ w
  4:50pm  up 18 days,  6:49,  4 users,  load average: 0.58, 0.62, 0.40
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU  WHAT
root     tty2     -                Sat 2pm  5:36m  0.24s  0.05s  -bash
willy	 :0       -                Sat 2pm   ?     0.00s   ?     -
willy	 pts/3    -                Sat 2pm 43:13  36.82s 36.82s  BitchX willy ir
willy    pts/2    -                Sat 2pm 43:13   0.13s  0.06s  /usr/bin/screen
+ echo

+ echo 'I'\''m setting two variables now.'
I'm setting two variables now.
+ COLOUR=black
+ VALUE=9
+ echo 'This is a string: '
This is a string:
+ echo 'And this is a number: '
And this is a number:
+ echo

+ echo 'I'\''m giving you back your prompt now.'
I'm giving you back your prompt now.
+ echo

	Future Bash Features
	There is now a full-fledged debugger for Bash, available at SourceForge. Right now however, you need a patched version of bash-2.05. The new debugging features might become available in bash-3.0.

Next: Debugging on part(s) of the script

Previous: Debugging Bash scripts

Sections

Personal tools

2.3.1. Debugging on the entire script