Let's say I have a completions scripts generated by gh completion -s fish and saved to an appropriate location. The question is: how do I update the script automatically on gh updates? Is there a plugin or should I do some scripting?
If gh completion -s fish is fast, you can just run it as the script that loads completions. Create a ~/.config/fish/completions/gh.fish with the following contents:
gh completion -s fish | source
Then it will be run on first load in each shell instance, though it won't reload during the lifetime of that instance.
Alternatively, you could set up a scheduled task (eg cron) or trigger depending on the operating system you are using.
Related
My question is whether it is possible to edit the crontab of a WSL2-based instance of Ubuntu with my Windows VSCode that is connected via WSL remote SSH.
If I type export EDITOR=code inside my WSL instance and then crontab -e, I am able to see a /tmp/crontab.sygFAU file load inside my VSCode instance.
The problem is that once I make edits to this file, it will save the file to /tmp/crontab.sysFAU but it doesn't actually take the next step of replacing the the real crontab file in /var/spool/cron/crontabs.
So once I re-open the crontab, it will just show what I had previously, and not my saved edits.
It would be nice to know if this is not possible or if there are any alternative ways to run a GUI editor because using nano is a pain!
An interesting question that I haven't considered before, myself. Here's what's happening:
You set your editor to code
You crontab -e, which properly loads VSCode with the temporary crontab.
However, because this is a Windows GUI application, it returns control to the parent Linux application (crontab) immediately after starting VSCode. You can see the same result if you just start notepad.exe from your shell in WSL -- Once Notepad starts (rather than exits) control is returned to the shell.
If you switch back to your terminal at this point, you'll see that crontab detected that the editor that it launched exited (returned), and so it has already tried to copy the temporary file to the permanent location.
However, since the temporary files doesn't yet have any changes, crontab decides there's nothing to do.
Editing the file in VSCode and saving it has no effect, other than to leave a dangling /tmp/... file hanging around (since crontab isn't there to clean up).
So what's the solution? We need a way to launch a Windows GUI application and prevent it from returning control to crontab until you are done editing.
I originally thought something from this question might work, but the problem is that the actual command that launches the Windows process is embedded in a shell script, which you can see with less "$(which code)" (or code "$(which code)"), but it's probably not a great idea to edit this.
So the next-best thing I came up with is a simple "wrapper" script around the (already-a-wrapper) code command. Create ~/.local/bin/code_no_fork.sh (could be anywhere) with:
#!/usr/bin/env bash
code $* > /dev/null
echo Press Spacebar to continue
read -r -s -d ' '
Credit: This answer for the Spacebar approach
Then:
EDITOR=~/.local/bin/code_no_fork crontab -e
After you make your edits in VSCode, simply press Space to allow the script to continue/exit, at which point crontab will (assuming no errors were detected) install the new Crontab.
Alternatives
This is should typically only be a problem with Windows GUI applications, so the other possible avenue is to simply use any Linux editor that doesn't fork. If you want a GUI editor, that's entirely possible as long as you are running a WSL release that includes WSLg support (now available for Windows 10 and 11).
I won't offer any individual editor suggestions since that would get into "opinion" and "software recommendation" territory, which is off-topic here.
In the past I've employed inotify for logging and as well as system functions. Now I'm in a position where I need to know each time an executable has been called, and a complete set of command line arguments passed in.
Short of setting up an auditd rule, is there any method to trigger on a particular executable being called, and return its command line arguments from user-space? I know the audit daemon can do this, so perhaps that's where I should look.
Monitoring process creation and termination events is a useful skill to have in you toolbox. This article consists of two parts. The first introduces exiting tools for diffrent platforms. The second explains how these tools work internally. 1
1 describes many tools, one tool named forkstat which uses the netlink2 and source code
Here are commands I used:
git clone https://github.com/ColinIanKing/forkstat.git
cd forkstat
make
sudo ./forkstat
In a separate ssh session I ran an ls command and observed this output:
Time Event PID Info Duration Process
09:43:49 fork 10362 parent -bash
09:43:49 fork 10433 child -bash
09:43:49 exec 10433 ls --color=auto
09:43:49 exit 10433 0 0.004s ls --color=auto
I have a perlscript file was running fine in crontab but suddenly it stopped running without any modification.
cd /home/user/public_html/crons && ./script.pl 2>&1 >/dev/null
The top of the script file is #!/usr/bin/perl -X
The output expect from this script is changes in database
I have another script file with the same modification and still works fine
When I run the file in the browser it works fine and execute all lines without any problem
I tried full path /usr/bin/perl but it didn't work
I tried Perl at the beginning but it didn't work
I run the command from SSH using putty but nothing happened
I checked log file /var/log/cron but no errors at all
I created temporary log file cd /home/user/public_html/crons/script.pl> /tmp/temp.log 2>&1 to see the errors but the log is empty
Here is the solution:-
I found the issue, There is was a stuck process for the same cron file , so i killed this process and its fixed
You can find your file process like this
ps aux | grep 'your cron file here'
This is a really common antipattern people seem to tend toward with cron.
Cron sends you an email with the output of your script, if it generates any output. People often redirect output to /dev/null to prevent cron from sending the email. This is bad because now the output of your script is lost entirely. Even if the script has some built-in logging, it might generate errors before it gets the log file opened and those are lost. It also might crash in a way that doesn't get written to the logging mechanism.
At a bare minimum, you should just remove 2>&1 >/dev/null to start receiving the email. (and also, test your mail setup using a temporary cron job like 1 * * * * echo "Test" )
The next better solution is to change it to >> /var/log/myscript/current.log and then also set up something to rotate the log files (like logrotate) and also make sure to create that directory with permissions that the script user is allowed to write to it. By only redirecting STDOUT of the script, any errors or warnings it writes to STDERR cause you to get an email, and if there are no errors/warnings the output goes to the log file and no email gets sent.
Neither of those changes solve the root problem though, which is that when cron runs your script it does so with a different environment than you have on the command line. What you really want is a way to run the script with a consistent environment, and log it. The "ultimate solution" is to define your task in some kind of service manager, and then use cron to occasionally start it. For instance, you could use systemd and define a service that doesn't restart, then use systemctl start my_custom.service in your cron job. Now you can test independent of cron, and your tests will have the same exact environment, and be logged by the service manager. As extra bonuses, you are protected from accidentally running your script twice at once, and you get a clean way to stop a running cron job without the danger of stale pid files.
I don't particularly advocate systemd myself, but thankfully there are lots of alternatives:
Runit : http://smarden.org/runit/runsvdir.8.html
S6 : https://skarnet.org/software/s6/
Perp : http://b0llix.net/perp/site.cgi?page=perpd.8
(but installing and configuring a service manager is a bigger task than just using systemd if your distro is based on systemd) Each of these allows you to define a service that doesn't restart. Then you use a shell command to issue a "run once" directive to the supervisor, which runs the task as a child. Now you can easily launch the jobs yourself and see all the errors in the log, and then add that command to the crontab and know that it will run identically when cron starts it.
Back to your original problem, once you get some logging you are likely to discover it is a permission problem or a upgraded module in the system perl.
I changed the environmental variable LD_LIBRARY_PATH from the Ubuntu terminal (because I was receiving an error) and the changes were applied when I ran code (a Python code) from the terminal. But when I ran the same script from the Visual Studio Code, the error remains. How to update the environmental variable so that Visual Studio Code sees it, as well?
Environment variables are passed from parent process to child process; they are not (say) global to the system or the user. If you change a variable in one shell, the change is only seen in that shell and any processes started from that shell. So the simplest solution is to change the variable and then start VSCode from that same shell:
$ export LD_LIBRARY_PATH=/some/useful/path
$ code
If you want to keep using that shell for other things, run it in the background:
$ code >/dev/null 2>&1 &
The redirection to /dev/null is needed because otherwise VSCode prints logging information periodically, and that output will be mixed with whatever else you're doing.
If you want to set the variable permanently, see the question How do I set a user environment variable? (permanently, not session). After following those instructions, you'll need to start a new shell (and possibly even logout and login) first so the settings take effect. Then launch VSCode from the new shell.
I have abc.jar file to deploy and run in remote machine.
I have transferred the file using jenkins, now what I have done is, call a a.bat batch file on remote machine using psexec in Execute Windows Batch Command.
a.bat executes the abc.jar
When the jar begins execution, the command prompt texts are stored in a file.
using java -jar abc.jar >> a.log 2>&1
Now what I want is to display the a.log contents in the jenkins console when the jar file is being executed
(the file is continuously being written and I want to show it in jenkins console as it is being written)
I have tried to do it using parallel processing by calling start twice, one for calling batch file, another using type for displaying.
But when I use start I get Process leaked file descriptor .
Is there any other way I can achieve this. Be it calling powershell or scheduled task in jenkins.
You need to look for tee equivalents in windows , there are few like GNU utilities for Win32, however if you have cygwin you can still use tee which will easy the prcoess.
Now the wuestion arises how to run my jar file on cygwin from jenkins ?
you can still use execute windows[batch] shell. and add cygwin installation path to the PATH variable and start using linux command like a BOSS.
or you can use powershell tee in built command from batch.