System exec

Hello,
I have a problem with the system exec, in many cases i will not get the output from the command.
I am executing many snmp commands and when i will execute them manually i will see the output but with the system exec the standard output will be empty.
Is there a way to make sure to "pull" out all the exec output?

Hello mike,
The problem is that it will show me the output in some cases but there are many others when the output will be empty.
I will attach the vi but you will have to have Alvarion's equipment for the snmp script to work.
Attachments:
SNMP script_exe.vi ‏30 KB
SNMP script_excute.ctl ‏5 KB

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How to capture keyboard strokes while focus is on an external app. Opened with system exec

Hi to the Forum,
I have an application that runs an external app. Through system exec, while this application is open the user needs to input a 6 digit serial number using the keyboard, I need to capture in parallel that information on my main VI in order to perform some information validations, such as the six digits were entered, the serial number is not repeated etc. I have read other post about the same issue but did not found a practical way to achieve a solution, please help with an example of how to do that as I'm on the final stage of the project.
Thanks in advance for your time and help.
MRDK

Hi MRDK,
You can/have to use Connectivity>>Input Device Control palette functions.
Attached is the simple example.
Regards,
Yogesh Redemptor
Regards,
Yogesh Redemptor
Attachments:
Get Keyboard Event.vi ‏15 KB

System exec cmd window

Hello, first time posting a question!
I have spent a good while trying to find an already posted answer to this, and looking on the wider web, hope i have not just missed it.
I am using XP Pro SP3, LV 8.6.
I am not very familiar with Windows command lines and structures etc.
I am using the System Exec VI to start a third party piece of software. I have wired the path in to the path input, and if i wire cmd /c start xxx to the command line terminal the VI will run and start the software application (xxx.exe). As the VI executes the cmd window clunks open and closed. If i run the VI without the cmd /c part of the command then an Error 2 is returned (as widely reported by others).
Is it possible to open an application without the cmd window opening and closing?
Using the System Exec VI it is possible to open NotePad just by wiring 'NotePad' to the comand line terminal. Is it possible to place the third party software somewhere, or register it with the OS somehow so it could be started in the same way as NotePad (i.e. without the cmd window flashing up)?
Thanks...
Blue
Message Edited by BlueTwo on 09-25-2008 09:22 AM

Hi Thoric, thanks for the suggestions, Success!
I tried the True boolean to the Run Minimized, but it did not help.
Changing the Environment Path string to include the path to the directory containing the application did work (once i had worked out the syntax).
On to the next problem....
Cheers,
Blue

Calling a VI which uses "system exec.vi" with LabVIEW run-time engine as adapter

Hi,
My TestStand sequence calls a VI which includes a call to "system exec.vi". When I try to load it in TestStand and if LabVIEW adapter is set to run-time engine, I get an error message "Unable to load Vi...". If I switch the adapter to "Development system", then it works fine.
Is there any way to use "system exec.vi" in a VI which is called in TestStand with LabVIEW run-time ?
Thanks,
Alex
Solved!
Go to Solution.

Hi Alex,
In you case, you are getting a -18002 error.
The reason is explained in the following link:
-18002 Errors in TestStand
http://digital.ni.com/public.nsf/allkb/D82FEAF0B4BA293A862575710053E252?OpenDocument
Please have a look at the 2nd reason. This is your case.
Hope it helps,
Regrads
Julien De Freitas / Applications Engineer / Certified LabVIEW Developer (CLD)
National Instruments Switzerland

System exec, How I say to open one file and make operation in external program?

Hi,
I got called an external program with the system exec.vi, but i would like the program open the file saved in the other window, i can get the file path, but how Can I put the file path in the external program and the program open the file and I tell (in this case compile), since i open one file code c and only i must to open and say to the program 'compile' and then close external program.
Any help?. Thanks.
Attachments:
system_exec.GIF ‏8 KB

Hi Fonsi,
System Exec.vi will allow you to run commands like launching a program easily but it is difficult and many times not possible to execute commands within an application.
A better way maybe to approach this though ActiveX. Please look at the following example that uses ActiveX to communicate with Excel.
Writing Rows to Excel 97 and Excel 2000 Using ActiveX
If you are not familiar to ActiveX and LabVIEW, please read the document below:
ActiveX and LabVIEW
I hope this
helps.
Sincerely,
Feroz
National Instruments

System Exec error message help

I have a piece of code as shown in the attached jpg. And I have it deployed just as shown, without the error cluster being wired. I use this piece of code to ping a server to see if it's there, meaning to see if it responds with a correct ping response. If so, I then move forward with writing a data file to that server that I write every half hour for days or weeks at a time. If the ping response is not correct, I simply go on and return one half hour later with even a larger (appended) data file to write. My main intent is to not have my code sit and wait, trying to write a file to a server that might not be there...
I've used this same code and technique for years without fail. Until recently. When it did finally fail, I got the worst of all possible outcomes where the ping command itself caused my code to hang with error messages I will provide shortly. And I'm hoping someone can tell me what would even cause a message like those below in the first place... The entire goal of using this ping of the server was to avoid having the "write file" command get held hostage by the server not being there... But if the ping command itself causes the code to put up error messages (and no one is there to monitor this typically) then that constitutes a situation where my cure became my problem.
See in the jpg where I use
ping -w 200 -n 1
followed by the name or IP address of the server. (that's what comes out of the "ping" control you see in the jpg).
The -w 200 modifier is a 200 ms timeout to wait.
The -n 1 is the number (1) of echo requests to send.
When this code fails, it puts up, in sequence, four messages like the one below. Note that this code is running from an executable that would be found on this Windows XP machine at
C:\Documents and Settings\xxxxuser\My Documents\my_executables\
The first of the four messages, each of which you have to click OK to to see the next one, is as follows.
The file C:\Documents and Settings\xxxxuser\My Documents\my_executables\-w could not be opened. No application was found to open that type of file
The second message is identical to the above except the "-w" is replaced by "200" (without the quotes).
Same with the third message except the "200" is now replaced by "1" (without the quotes).
Same again with the fourth message except the "1" is now replaced by the full name of the server, eg., "myserver.abc.com" (without the quotes).
Clearly the System Exec.vi (see that in jpg) is parsing up the ping command, but skipping over the "-n" component(???), and it thinks it's supposed to try to open some non-existent file at the same file location as the executable that is executing my code.
I get this result rarely so it's hard to figure out what's going on. Anyone have any ideas what might cause such an error and any hints on how to prevent this show stopping error from occurring??? Do I perhaps just need to practice better programming and wire the error cluster on System Exec.vi???
Any thoughts or help would be much appreciated... thanks.. bob..
Attachments:
ping pic.jpg ‏19 KB

It appears to me that your ping command is getting mangled on its way to the command shell, like something is interrupting it or trying to run at the same time.
When it says the executable cannot be opened, I believe that is because it's trying to process that character or string as its own separate command, instead of as a flag of your ping command.
I don't know why that would happen or what outside program could be interfering with your call to the command shell.
I do think that Wart's suggestion is a good one: the cmd /c part should send the command through a slightly different channel that may preven this interference.
Chris
Certified LabVIEW Architect
Certified TestStand Architect

How do you change the directory of system exec after it has ran once in the current vi

Hi all,
Attached is the sub vi that i am running in my main application. I run it twice and change the directory of the file to run. It appears that after i run this vi that i cant change the directory and it tries to run a file from the incorrect directory. Does anyone have any advice on how to fix this issue?
Attachments:
system execute command.vi ‏41 KB

matt198717 wrote:
Hi all,
Attached is the sub vi that i am running in my main application. I run it twice and change the directory of the file to run. It appears that after i run this vi that i cant change the directory and it tries to run a file from the incorrect directory. Does anyone have any advice on how to fix this issue?
I am not sure, if I understand exactly the problem, but do you really need the cmd /c start some_executable.exe. This executes a command prompt window, which executes another command prompt window, where your executable runs.
You can just use cmd /c some_executable.exe some_parameters_if_needed, and you don't need any quotation marks, even if the executable has command line parameters. I you want that the executable runs in particular directory, wire this path to the 'working directory' of System Exec.vi

How do I determine expected output size for System Exec vi

I am running a DOS exe from a Batch file using the System Exec vi. My exe is programming software for a microcontroller and passes data to the programmer via the serial port. When I run the batch file externaly to LabView it works fine. When I run the same batch file using the System Exec vi I get an error from the programmer app (DOS app). Not every time but usually within 20 attempts. I reduced the execution priority of my vi's to give more time to the DOS window. This seems to have helped but hasn't solved the problem completely. I read in the help file that LabView will run more efficiently if you specifiy the expected output size in the System Exec vi, but how do I determine it? Is the expected output
size the size of the bat file I call?

> I am running a DOS exe from a Batch file using the System Exec vi. My
> exe is programming software for a microcontroller and passes data to
> the programmer via the serial port. When I run the batch file
> externaly to LabView it works fine. When I run the same batch file
> using the System Exec vi I get an error from the programmer app (DOS
> app). Not every time but usually within 20 attempts. I reduced the
> execution priority of my vi's to give more time to the DOS window.
> This seems to have helped but hasn't solved the problem completely. I
> read in the help file that LabView will run more efficiently if you
> specifiy the expected output size in the System Exec vi, but how do I
> determine it? Is the expected output size the size of the bat fi
le I
> call?
If you think it is due to timing, and you wish to yield to the DOS app,
don't just lower the priority of LV, but use Wait ms to put overeager
diagram elements to sleep and limit their loop rate. Use the task
manager or performance monitor of the computer to determint if this is
the issue.
Greg McKaskle

Windows system exec error in application causes app to crash

The basics:
LabView 11.0 (32-bit)
Windows 7 enterprise
Because I have to control an elevated app I run my built app elevated on a Win7 64 machine.
I have an application that uses the system exec.vi (attached) to get a portion of the arp table. When I run this in development it works great. However when I build an app and run it this vi causes the app to be unstable and crash.... sometimes. I have a troubleshooting vi that I wrote that I place at the start and end of vis. This puts a log file on my desktop so that I can trace where it crashes. I've attached the log as well.
Basically we have a power controller that we control by Telnet but 1st I have to get the IP. I have the MAC of the controller which is DHCP but not the IP. To get the IP I fill the ARP table and search it for the MAC.
get ARPCache.vi throws the error messaage: System Exec.vi . Command was "cmd /c "arp -a | find "192.168.120"" but only in the built app.
Update: While getting more info to complete this post I did a build where I changed "get ARPCachs.vi" to show when called so I could see the error cluster. Now it pops up but no errors. hmmm
Norm
Attachments:
get ARPCache.vi ‏22 KB
Log program message start finish.vi ‏24 KB
Program Log.txt ‏2 KB

It depends on how the exe deals with the arguments. Some do honor escape characters, some not.....
Afaik, there is no difference regarding the System Exec in development environment vs. exe. But it is possible, that these are executed using different user rights?
Norbert
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.

Creating a delay in labview until a c program completes in system exec.vi without using "wait until completeion"

I want to run two related C programs. The second one reads a text file that the first created. So I need to wait until the first is completed.
I use "system exec.vi" and I know I can set "wait until completeion" to true, but this way I won't see the screen and the C program announcments. Someone has an idea?

Hi Dror,
my idea: just wait for the text file created by the first C program. Check for the presence of this file (maybe using 'list directory') or check for the size of this file...
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

How can I run different commands in the same system exec window?

I want to open a window (cygwin) on my Xp machine and sent commands within that window. I then have to monitor what the responses are coming back into the window that was launched. Any ideas on how to do this? I have been playing with the system exec VI but can't seem to get it to do what I want. Any help would be appreciated. Thanks - Troy

Hello,
Have you tried setting the wait until completion to true on the System Exec VI? If so, the LabVIEW documentation claims that the parameter "standard output returns information from the program you called if wait until completion is TRUE. If wait until completion is FALSE, System Exec returns an empty string."
Could this be the answer to the problem of getting the data returned?
I hope this helps!
Best Regards,
JLS
Best,
JLS
Sixclear

Question about calling batch file by using the System Exec+.vi?

Hi
I have a problem about calling batch file. I know that the system exec is equivalent to "run" in Windows. I called the batch file c:\rtxdos\bs\ch0.bat successfully in the "run" but it didn't work in the LabVIEW program. The dos prompt had an error message "Bad command or file name" and it just happen when I call this batch file in LabVIEW. Why?
Bill.

Hi,
Try to set the "working directory" parameter of System exec.vi to the directory where the batch file is located. It may help.
Good luck.
Oleg Chutko.

Why I get an error when I call Snipping Tool with System Exec?

Hi to everyone, I want to call Snipping Tool from LabVIEW using the System Exec VI, but I always get an error 2; this not happen when I call another executables like calculator or paint; I hope someone can help me or tell me why this error occurs.
Thanks in advance, I have attached a couple of images of the VI that I have done so far.
Solved!
Go to Solution.
Attachments:
block diagram.PNG ‏11 KB

Hey there ;
I am guessing you are using the command: SnippingTool or SnippingTool.exe, just as you would use mspaint; but it is giving you Error 2; this is a Windows Issue more than a LabVIEW one, ,you can try using command:
C:\Windows\Sysnative\snippingtool.exe;
it worked for me; i found this info in the KB below.
Command Not Recognized When Using System Exec VI
Good luck

System.exec() in jdk.15 and later

HI there
I have used System.exec() in jdk 1.4 and I came across that, in jdk 1.5 and later you have better way to do the same thing. Can anyone help how to make it better with jdk 1.5 and later.
Thanks
Arif.

I assume you mean Runtime.exec()?
The "better way" is called ProcessBuilder. Check out the API docs for that, and Google "Java ProcessBuilder example". You will get plenty of hits. Many of the Runtime.exec() traps still exist, even for this, however, but all of the traps related to the command being a single String are elimanted, in any case.

System Exec FFMPEG

Hello!
I'm trying to merge audio and video previously adquired in labview, and I can do it with the FFmpeg tool by typing
"ffmpeg -i video.wav -i video.avi -c copy output.avi" on the FFmpeg console.
I would like to do it programatically, so I think I need to use the System Exec Utility. I have tried this:
But it does nothing. I think I'm not setting the input line correctly. Do I have to set the command in the Standar Input as I do in the command line from the FFmpeg Console?
I would be greatfull if anybody could help me.
Thanks in advance for your time!
Guille.
Solved!
Go to Solution.

Hi,
Perhaps you could try testing System Exec.vi using simple commands.
Read this link: http://digital.ni.com/public.nsf/allkb/8E19CA81874FFDD786256BE40066C151 , I believe there are 2 screenshots which shows 2 different methods of writing command using system exec. What I can see from your screenshot is that you're using both at the same time. Can you try using the method found in the link (1st screenshot) instead?
Here's an example which you can refer to and play around with: https://decibel.ni.com/content/docs/DOC-1109
Warmest regards,
Lennard.C
Learning new things everyday...

System exec+ problem

I'm using the system exec+ file to read in a msdos executable into labview, and to have it stay open until the user exits. Whats happening now is that when its reading in my program (awc.exe), it pops up an error message (in dos) that says "cannot find fonts." The font files are in the directory (c:\awc) with the executable. Do I need to link the font files somehow to awc.exe, or is this being caused by some other problem?

jdaltonnal wrote:
> I'm using the system exec+ file to read in a msdos executable into
> labview, and to have it stay open until the user exits. Whats
> happening now is that when its reading in my program (awc.exe), it
> pops up an error message (in dos) that says "cannot find fonts." The
> font files are in the directory (c:\awc) with the executable. Do I
> need to link the font files somehow to awc.exe, or is this being
> caused by some other problem?
Not sure about your awc.exe prog but I have had similar problems with
other exe progs.
The awc program is probably expecting c:\awc is set as the dos current
directory; I don't think exec+ does this.
Try this:
Open a dos session manually in Windows.
Don't change directory; keep the default one dos gives you.
Type in the
command you are passing to exec+; maybe c:\awc\awc.exe (or
just awc.exe if c:\awc has been set in your path?) What happens?. Same
problem? So now try running awc.exe again but first change to c:\awc
directory. Does it now work ok. If so you need to set c:\awc as the
working directory from within exec+. To complicate things you must set
this current directory in the same dos session as awc.exe is called so
you can't do this by running two exec+ commands.
I use the following technique. Write a .bat (just a text file saved with
the file extension .bat). You could call this awc.bat
In this file put something like:
c:
cd \awc
awc.exe
then call exec+ to execute awc.bat instead of awc.exe
You will need to tell exec+ to wait for execution to finish but I guess
you already know that.
Hope this works for you.
Dave.

System exec

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