moro blog

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4

Launch an batch script without the command line window

Hi folks, today we are going to talk a bit about a useful windows scripting trick that allows you to launch a batch script without seeing the extra CMD window popping up.

Using a .exe launcher

So you already have a batch file. The solution to avoid the Command Line Window opening is to convert that batch file to an .exe file. That can be achieved using Bat To Exe-Converter.

The interface is simple, I let you figure it out :)

IMPORTANT : Don’t forget to select "Invisible application" in the visibility section.

One .batch to rule them all

I used to have a lot of batch files that needed to be launched from the Windows Start Menu. But I didn’t want to create an .exe file for each of them because it would have been complex to maintain.

So I wanted a way to have a unique .exe file taking a .bat file as argument. Here is how that can be achieved :

First, we need to create a .bat file that can execute another .bat file that is passed as argument. The solution is very short, here is the content of such a .bat file :

%*

Yes ! That’s it ! That basically takes every arguments passed and execute that. However this will pop another CMD window up since it launches a batch file, so you should use this instead to launch it in the background :

start /b %*

This is already very good and will answer most needs. However, note that when the child batch script finishes, you will have a remaining CMD process (with no parent, completely independant).

To have this CMD process to terminate when the child batch script is over, you need to specify it like that :

start /b cmd /c %*

Now you convert THAT little script to an .exe file with the software mentioned above and there you go :)

Auteur: Benjamin Jaton

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11

2

Linux : force the DNS used

If you really want to force which Domain Name Server(s) to use on you system, here is one way :

First, edit the file /etc/resolv.conf to match the configuration needed

Second, set the immutable bit on the file :

sudo chattr +i /etc/resolv.conf

That way, even a root process won’t be able to modify that file.

You can undo that with :

sudo chattr -i /etc/resolv.conf

Hope this help !

Auteur: Benjamin Jaton

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11

16

Maven java webapp and jetty

I very often use the jetty-maven-plugin in my Java Webapps. Basically it allows you to be able to run any webapp right after having checked out the project with the simple command :

mvn jetty:run-exploded

Then go by default on http://localhost:8080/ and you’ll have a link to your webapp :) Very quick. You will find all the details of the configuration on the plugin’s homepage (ports, realms, contextPath, ...)

I usually use the same command to launch jetty :

MAVEN_OPTS="-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,address=4000,server=y,suspend=n" mvn clean jetty:run-exploded

I always use that to always have the debugging activated on port 4000.

Auteur: Benjamin Jaton

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11

10

Shell : cd current directory

Quick post to share a useful command that I often use in my scripts to make sure that I know where "I am" :

cd $(readlink -f $(dirname $0))

Explanation :

$0 is the first element of the command line invoked = the script itself

dirname will give us the directory to that script

readlink -f will expand and resolve any link in the path

Obviously in some cases this shall not be used :)

Auteur: Benjamin Jaton

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11

27

Linux : File descriptor limits

Sometimes a software can be refused the opening of a new resource by the Operating System because it has reached the maximum number of file descriptors used. This is usually cause by a code poorly implemented forgetting to properly close() the resources used.

Under Linux, you can know those limits with those commands :

$ ulimit -Sn 1024 $ ulimit -Hn 1024

The "soft" limit (-Sn) represents the maximum number of file descriptors allowed per process. It can be changed but cannot exceed the "hard" limit. Here we have 1024 for both.

To change the limit, use :

$ ulimit -n 512

To see more on the global limits on your system, use :

$ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 20 file size (blocks, -f) unlimited pending signals (-i) 16382 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) unlimited virtual memory (kbytes, -v) unlimited file locks (-x) unlimited

More : read this short article on Linux scalability.

Auteur: Benjamin Jaton

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Moro

Launch an batch script without the command line window

Using a .exe launcher

One .batch to rule them all

Linux : force the DNS used

Maven java webapp and jetty

Shell : cd current directory

Linux : File descriptor limits