Difference between revisions of "Debug a script"
m (Text replacement - "<source lang="bash">" to "<syntaxhighlight lang="bash" >") |
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You need to run a shell script with -x option from the command line itself: | You need to run a shell script with -x option from the command line itself: | ||
| − | < | + | <syntaxhighlight lang="bash" >bash -x script-name</source> |
OR | OR | ||
| − | < | + | <syntaxhighlight lang="bash" >bash -xv script-name</source> |
You can also modify [[shebang]] line to run an entire script in debugging mode: | You can also modify [[shebang]] line to run an entire script in debugging mode: | ||
| − | < | + | <syntaxhighlight lang="bash" >#!/bin/bash -x |
echo "Hello ${LOGNAME}" | echo "Hello ${LOGNAME}" | ||
echo "Today is $(date)" | echo "Today is $(date)" | ||
| Line 18: | Line 18: | ||
* set -v : Display shell input lines as they are read. | * set -v : Display shell input lines as they are read. | ||
* set -n : Read commands but do not execute them. This may be used to check a shell script for syntax errors. | * set -n : Read commands but do not execute them. This may be used to check a shell script for syntax errors. | ||
| − | < | + | <syntaxhighlight lang="bash" >#!/bin/bash |
### Turn on debug mode ### | ### Turn on debug mode ### | ||
set -x | set -x | ||
| Line 34: | Line 34: | ||
Another example using set -n and set -o noexec: | Another example using set -n and set -o noexec: | ||
| − | < | + | <syntaxhighlight lang="bash" >#!/bin/bash |
set -n # only read command but do not execute them | set -n # only read command but do not execute them | ||
set -o noexec | set -o noexec | ||
Revision as of 22:49, 29 March 2016
← Execute a script • Home • Chapter 2 Challenges →
You need to run a shell script with -x option from the command line itself: <syntaxhighlight lang="bash" >bash -x script-name</source> OR <syntaxhighlight lang="bash" >bash -xv script-name</source> You can also modify shebang line to run an entire script in debugging mode: <syntaxhighlight lang="bash" >#!/bin/bash -x echo "Hello ${LOGNAME}" echo "Today is $(date)" echo "Users currently on the machine, and their processes:" w</source>
Use of set builtin command
Bash shell offers debugging options which can be turned on or off using set command.
- set -x : Display commands and their arguments as they are executed.
- set -v : Display shell input lines as they are read.
- set -n : Read commands but do not execute them. This may be used to check a shell script for syntax errors.
<syntaxhighlight lang="bash" >#!/bin/bash
- Turn on debug mode ###
set -x
- Run shell commands
echo "Hello $(LOGNAME)" echo "Today is $(date)" echo "Users currently on the machine, and their processes:"
- Turn OFF debug mode ###
set +x
- Add more commands without debug mode
</source>
Another example using set -n and set -o noexec: <syntaxhighlight lang="bash" >#!/bin/bash set -n # only read command but do not execute them set -o noexec echo "This is a test"
- no file is created as bash will only read commands but do not executes them
>/tmp/debug.txt</source>
See also
External links
- How to debug a Shell Script under Linux or UNIX.