If I enter bash -x option, it will show all the line. But the script will execute normally.
How can I execute line by line? Than I can see if it do the correct thing, or I abort and fix the bug. The same effect is put a read in every line.
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2Perhaps more broadly see also stackoverflow.com/questions/951336/how-to-debug-a-bash-script/…tripleee– tripleee2017-10-02 04:54:05 +00:00Commented Oct 2, 2017 at 4:54
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5 Answers
You don't need to put a read in everyline, just add a trap like the following into your bash script, it has the effect you want, eg.
#!/usr/bin/env bash
set -x
trap read debug
< YOUR CODE HERE >
Works, just tested it with bash v4.2.8 and v3.2.25.
IMPROVED VERSION
If your script is reading content from files, the above listed will not work. A workaround could look like the following example.
#!/usr/bin/env bash
echo "Press CTRL+C to proceed."
trap "pkill -f 'sleep 1h'" INT
trap "set +x ; sleep 1h ; set -x" DEBUG
< YOUR CODE HERE >
To stop the script you would have to kill it from another shell in this case.
ALTERNATIVE1
If you simply want to wait a few seconds before proceeding to the next command in your script the following example could work for you.
#!/usr/bin/env bash
trap "set +x; sleep 5; set -x" DEBUG
< YOUR CODE HERE >
I'm adding set +x and set -x within the trap command to make the output more readable.
9 Comments
David Doria
Then how do you step to the next line (run the next command)?
organic-mashup
It traps a read on every command. Only thing you need to do is pressing return to get to the next command
mug896
if you have command lines like this "while read line; do echo $line; done < somefile" that method does not work because "trap read DEBUG" read line from somefile
slashdottir
How do you make it stop? After I step through the script to the end, the shell acts like the script is still running.
user3132194
Change to
trap 'read -u1' debug to override file read redirection problem. |
The BASH Debugger Project is "a source-code debugger for bash that follows the gdb command syntax."
8 Comments
studgeek
This is really the best solution. It allows viewing the line before it is run (and much more). On most systems it can be installed with
apt-get install bashdb. Then you just need to run bashdb your_command.sh, type step, and then hit carriage return after that.
Sajuuk
@studgeek it is not available on Redhat/CentOS etc. so I would not call that "most systems".
Charles Duffy
@Sajuuk, it may not be packaged, but it's absolutely available.
boweeb
macOS:
brew install bashdb
Dan Dascalescu
@CharlesDuffy: it's not in the default Ubuntu repos either.
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If your bash script is really a bunch of one off commands that you want to run one by one, you could do something like this, which runs each command one by one when you increment a variable LN, corresponding to the line number you want to run. This allows you to just run the last command again super easy, and then you just increment the variable to go to the next command.
Assuming your commands are in a file "it.sh", run the following, one by one.
$ cat it.sh
echo "hi there"
date
ls -la /etc/passwd
$ $(LN=1 && cat it.sh | head -n$LN | tail -n1)
"hi there"
$ $(LN=2 && cat it.sh | head -n$LN | tail -n1)
Wed Feb 28 10:58:52 AST 2018
$ $(LN=3 && cat it.sh | head -n$LN | tail -n1)
-rw-r--r-- 1 root wheel 6774 Oct 2 21:29 /etc/passwd
2 Comments
see
This does not work for multi-line commands
Brad Parks
yeah for sure - I do mention that in the description though - so if you have
if statements that aren't on one line, or while loops, etc, it wont work for that!Have a look at bash-stepping-xtrace.
It allows stepping xtrace.
Comments
xargs: can filter lines
cat .bashrc | xargs -0 -l -d \\n bash
- -0 Treat as raw input (no escaping)
- -l Separate each line (Not by default for performances)
- -d \\n The line separator
