Besides using top, is there a more precise way of identifying if the last executed command has finished if I had to check in a separate session over Putty?
pgrep
How about getting it to run another command immediately after that sets a flag.
$ do_command ; touch I_FINISHED
then when the command finishes it'll create a file called I_FINISHED that you
can look for.
or something more sophisticated that writes to a log file if you're doing it
multiple times.
I agree that it may be a faster option in the long run to have your program write to a log file or create a notification. Just put it at the end of the executed code, past the part that you suspect may cause it to hang.
ps -eo cmd
Lists all processes, and displays the command line, as 'typed' when the command started, so you will be able to tell your script apart from anything else running written in Perl.
Related
I am learning Linux and need to write a shell script that will kill all processes whenever another command runs on it. I know how to write a script with a variable, but cannot seem to find ways of doing it for a command.
I would imagine that I need to find a way to evaluate if the command is true or not and to use that as the condition for an if statement. But anything I try returns errors.
Linux is the first CS related thing that I am learning and I am absolutely stuck at this step. I tried searching for this but am not quiet sure what to write.
It's the sh shell.
Edit: Whenever a program is executed with a certain command I need the script to terminate it right away.
In general you can use this construct in a bash conditional:
if [ "$(whoami)" -ne "0" ] then;
Where the whoami is an example for a an existing script. Obviously the same is possible with many other notations, not only the if conditional. Take a look at the test command, it is very helpful for such things.
For more details take a look at the "man page" bash brings along: man bash
The "Linux man pages" offer a wealth of information.
We have put together a perl script that essentially looks at the argument that is being passed to it checks if is creating or modifying a file then it saves that in a mysql database so that it is easily accessible later. Here is the interesting part, how do I make this perl script run before all of the commands typed in the terminal. I need to make this dummy proof so people don't forget to run it.
Sorry I didn't formulate this question properly. What I want to do is prepend to each command such that each command will run like so "./run.pl ls" for example. That way I can track file changes if the command is mv or it creates an out file for example. The script pretty much takes care of that but I just don't know how to run it seamlessly to the user.
I am running ubuntu server with the bash terminal.
Thanks
If I understood correctly you need to execute a function before running every command, something similar to preexec and precmd in zsh.
Unfortunately bash doesn't have a native support for this but you can do it using DEBUG trap.
Here is a sample code applying this method.
This page also provide some useful information.
You can modify the ~/.bashrc file and launch your script there. Do note that each user would (and should) still have the privelege to modify this file, potentially removing the script invocation.
The /etc/bash.bashrc file is system-wide and only changeable by root.
These .bashrcs are executed when a new instance of bash is created (e.g. new terminal).
It is not the same as sh, the system shell, that is dash on Ubuntu systems.
I currently have an issue whilst running a shell script in UNIX which would be easily solved if I could record the processes which are spawned during a run of my script. I'd thought to use the top command and record to a file e.g.
top > tmp.txt
I think this would not be applicable however as it only refreshes periodically. Does anybody know how this would be possible? Ideally it would be something like this:
pid:123 my_script.sh
pid:124 grep...
pid:125 ...
pid:126 ...
You get the idea.
Kind Regards,
JLove
Top has a "batch mode", which will send the latest "top" results to standard output.
You can do something like this:
top -bn3
Which will print the top results three times to standard output.
It sounds like you just want to know the pids of all processes that have your shell script as an ancestor. ps --forest or pstree should give you what you need.
I have a simple command in a Linux shell script (say foo.sh). In it I do this:
export INSTALL_DIR=/mnt/share/TEST_Linux
I run the script with:
> sh foo.sh
When it finishes I try to get the variable but the value is blank.
> echo $INSTALL_DIR
If I type the command directly the exported var becomes global to the opened terminal window. I'm using Ubuntu.
Setting environment variables is local to the child bash process running your script. To achieve what you want, you need to source it like this: source foo.sh. It means that it's run by your main bash process. Then, the setting of a variable will remain after the script is finished.
The variable is exported only in the new shell you are starting. You probably want to execute your script with source.
source foo.sh
I don't know the answer but i know how to overcome it.
# source ./foo.sh
# echo $INSTALL_DIR
And it's like magic.
I think it's because that script gets executed in it's own "shell". Not sure.
Because the process you are running (the shell running your script) can do whatever it wants, but its actions won't affect the parent process (your current shell).
A somewhat weird analogy would be: I can take 5 tequila shots and my environment will become blurry and gravity laws would be affected according to my perception. But to my father, his environment is the same, he doesn't get drunk because of my actions.
If you want that variables created/altered in your script affect your current shell, you should source the script as other answers pointed out. Please do note that doing this also may change the resulting working dir in your shell if the script does cd /whatever/path, that any other functions setted, but also altered or removed, would get affected in the same way in your shell.
A really weird and not very good analogy would be if I take 5 tekila shots and then my father kills me and drinks my blood.
Am I disturbed or what? ;-)
Some programs return immediately when launched from the command line, Firefox for example. Most utilities (and all the programs I've written) are tied to the shell that created them. If you control-c the command line, the program's dead.
What do you have to add to a program or a shell script to get the return-immediately behavior? I guess I'm asking two questions there, one for shell scripts and one for general, if they're different. I would be particularly interested to know if there's a way to get an executable jar to do it.
I'm almost embarrassed to ask that one but I can't find the answer myself.
Thanks!
start cmd
on Windows,
cmd &
on *nux
Here substitute
cmd = java -jar JarFile.jar
On *nux the fg and bg commands are your friends as well ...
You need to basically need to fork a process or create a new thread (or pretend to)
in *nux you can do this with an & after the command like this /long/script & or in windows you can create a BATCH file that executes your processes then exits (it does this naturally).
NOTE: there's no particularly good way to reference this process after you're forked it, basically only ps for the process list. if you want to be able to see what the process is doing, check out using screen (another linux command) that will start a session for you and let you "re-attach" to the screen.
to do this, install screen (sudo apt-get install screen or yum install screen). then type screen to create a new session (note, it will look like you didn't do anything). then, run your /long/command (without the &), then press CTRL + A + D (at the same time) to detach from it (it's still running!). then, when you want to re-attach, type screen -r.
Additionally, look for flags in any help message that allow you do this without using the above options (for instance in synergy you can say synergy --background)
A wrapper script consisting of nothing but:
your_prog_or_script &
Will launch the target and exit immediately. You can add nohup to the beginning of that line so it will continue running if the shell is exited.
For an executable program (as opposed to a shell script), on Linux/Unix use fork() and exec() and then exit the parent process, which will return to the shell. For details see the man pages, or some page like http://www.yolinux.com/TUTORIALS/ForkExecProcesses.html.