Remote Debugging Shell scripts

unev_21 · 03-12-2009, 05:05 AM

Hi All,

Is there any way to remotely debug shell scripts? I know we can do the same for executables using gdbserver and ddd.

I was successful attaching the shell script in remote Linux box to gdbserver. But when I invoked ddd using arguments 'bashdb' and tried to debug it, it doen't seem to work..

Any thoughts ppl??

Regards,
unev_21.

T74marcell · 03-12-2009, 06:14 AM

You could try setting up a vncserver on the remote server and run the whole debugging session via VNC. That way you have an almost complete GUI session, just as when sitting in front of that server physically. Can be a bit slow, but should work otherwise.

Arch Linux

jlinkels · 03-12-2009, 08:36 AM

Shell scripts cannot be debugged using a debugger, bash lacks the capabilities to provide the hooks for a debugger. (You can debug the bash executable that is, but that is not your goal) You have to insert echo statements in smart places. It also helps to run the script with

Code:

sh -x myscript.sh

As for the remote, set up an SSH session to the remote server and run the script in that session. No need for VNC as bash scripts are usually console based if you don't call GUI programs from the script.

jlinkels

unev_21 · 03-12-2009, 02:11 PM

thanks jlinkels & T74marcell.

I was able to locally debug shell scripts by attaching bashbd to ddd. I was expecting someting similar even in remote mode.

The linux box doesn't have ssh server installed, only telnet. I tried installing ssh, but it said no valid C++ compiler was found. In that case I presume even gcc is not installed in that box. And, to add to the worries, it doesnt have anymore free space to install applications. I use a 256MB flash card & debian dist in the box.

I guess as you said sh -x is the best solution for the moment.

unev_21

jlinkels · 03-12-2009, 03:03 PM

SSH and Telnet should provide an equal connection as seen from any application. The difference is that Telnet is not secure while SSH is. Therefor on most boxes Telnet is diabled. If it is there and SSH is not, you should be able to work over Telnet.

jlinkels

askervin · 10-17-2019, 06:01 AM

Sometimes it could be enough to make the script call home to you with netcat (nc). Add a line to your script:

Code:

mkfifo /tmp/f ; cat /tmp/f | sh -i 2>&1 | nc HOMEHOST HOMEPORT > /tmp/f

and wait for it to call at HOMEHOST:

Code:

$ nc -k -l -p HOMEPORT

This gives you (sub)shell prompt where you can inspect cwd, file system, running processes, exported variables etc. at the point where the script is running.

If you need access to local variables and functions in the shell script, you can use more complex form of the same call-home idea. See:

https://01.org/fmbt/blogs/ask/2019/d...emote-scripts/