How does the OS know what files to start first? - operating-system

I can't figure out how the OS knows what files to start first... Like how does it know to run the script which lets you login, instead of another random file. How is the file executed on bootup specified?

It's a program. It can contain names of other program(s) to execute when needed and in whatever order desired. It can also take that information from a file. I see no conceptual problem here.

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how to move file after reading the file in ibm datastage

i have 1 folder which has 4 files, they are sales_jan, sales_feb, debt_jan, debt_feb.I created specific job for each sales and debt. The thing is, if i already run the job previously for sales_jan only and then there comes sales_feb after that, i dont wanna repeat reading the sales_jan again, i only want to read the newest file added that hasn't been processed. For reading the file, i pass the pattern of the specific file (ex. sales_*) but if i use it like that, then the stage will reprocessed the sales_jan again although it already has. I want to move the file already been read into another folder. How do i exactly do it in ibm datastage? if there's no way to do it, what's your suggestion for my problem. Any ideas would be appreciated.
The easiest solution is to use an after-job subroutine (ExecSH on Linux/UNIX, ExecDOS on Windows) to move the file to a different location.
Since you're using wildcards for the Sequential File stage, you're going to have to be a bit more clever in handling a situation where your job processes only some of the files. I would prefer to write this using a loop in a sequence, processing one file at a time, so that the move can be handled per-file.
you might make a flag for every file which already read by your job. For example add a maxdate field for each file. When the first file max date is less than the second file or new file Then read the latest file. It can be done by using simple linux command in sequence or tranformer. Just like Ray mentioned before

MATLAB doesn't find files I downloaded while the script is running

My problem is as described. My script downloads files through an external call to cmd (using the system function and then .NET to make keypresses). The issue is that when it tries to fopen these files I downloaded (filenames from a text file I write as I download), it doesn't find them, causing an error. When I run the script again after seeing it fail, it works but only up to the point where it's trying to download/call new files again, where it runs into the same problem.
Are new files downloaded during when a script is running somehow not visible to the search path? Because the folder is most definitely in my search path (seeing as it works outside of during-script downloads). It's not that it isn't getting the files fast enough either, cause they appear in my folder almost instantly, and I've tried a delay to allow for it to recognize it, but that didn't work either.
I'm not sure if it's important to note that the script calls an external function which tries to read the files from the .txt list I create in the main script.
Any ideas?
The script to download the files looks like so:
NET.addAssembly('System.Windows.Forms');
sendkey = #(strkey) System.Windows.Forms.SendKeys.SendWait(strkey);
system('start cygwinbatch.bat')
pause(.1)
sendkey(callStr1)
sendkey('{ENTER}')
pause(.1)
sendkey(callStr2)
sendkey('{ENTER}')
pause(.1)
sendkey('exit')
pause(2)
sendkey('{ENTER}')
But that is not the main reason I am asking: I am confident that the downloads are occurring when the script calls them, because I see them appearing in my folder as it called. I am more confused as to why MATLAB doesn't seem to know they are there while the script is running, and I have to stop it and run it again for it to recognize the ones I've downloaded already.
Thank you,
Aaron
The answer here is probably to run the 'rehash' function. Matlab does not look for new files while executing an operation, and in some environments misses new files even during interactive activity.
Running the rehash function forces Matlab to search through its full path and determine if there are any new files.
I've never tried to run rehash in the middle of an operation though. ...
My guess is that the MATLAB interpreter is trying to look ahead and is throwing errors based on a snapshot of what the filesystem looked like before the files were downloaded. Do you get different behavior if you run it one line at a time using F9? If that's the case then you may be able to prevent the interpreter from looking ahead by using eval().

use matlab to open a file with an outside program and execute 'save as'

Alright, here's what I'm dealing with (you can skip to TLDR if all you need to see is what I want to run):
I'm having an issue with file formatting for a nasty conglomeration of several ancient programs I've strung together. I have some data in .CSV format, and I need to put it into .SPC format. I've tried a set of proprietary MATLAB programs called 'GS tools' for fast and easy conversion, but fast and easy doesn't look like its gonna happen here since there are discrepancies in how .spc files are organized now and how they were organized back when my ancient programs were written.
If I could find the source code for the old programs I could probably alter the GS tools code to write my .spc files appropriately, but all I can find are broken links circa 2002 and earlier. Seeing as I don't know what my programs are looking for, I have no choice but to try resaving my data with other programs until one of them produces something workable.
I found my Cinderella program: if I open the data I have in a program called Spekwin and save the file with a .spc extension... viola! Everything else runs on those files. The problem is that I have hundreds of these files and I'd like to automate the conversion process.
I either need to extract the writing rubric Spekwin uses for .spc files (I believe that info is stored in a dll file within the program, but I'm not sure if that actually makes sense) and use it as a rule to write a file from my input data, or I need a piece of code that will open a file with Spekwin, tell Spekwin to save that file under the .spc extension, and terminate Spekwin.
TLDR: Need a command that tells the computer to open a file with a certain program, save that file under a different extension through that program (essentially open*.csv>save as>*.spc), then terminate the program.
OR--I need a way to tell MATLAB to write a file according to rules specified by a .dll, but I'm not sure I fully understand what that entails.
Of course I'm open to suggestions on other ways to handle this.

Please help me with a Power shell Script which rearranges Paths

I have both Sybase and MSFT SQL Servers installed. There is a time when Sybase interferes with MS SQL because they have they have some overlapping commands.
So, I need two scripts:
A) When runs, script A backs up the current path, grabs all paths that contain sybase or SYBASE or SyBASE (you get the point) in them and move them all at the very end of the path, while preserving the order.
B) When it runs, script B restores the path from back-up.
Both script a and script b should affect the path immediately. So, if a.bat that calls patha.ps1, pathb.ps1 looks like so:
#REM Old path here
call patha.ps1
#REM At this point the effective path should be different.
call pathb.ps1
#REM Effective old path again
Please let me know if this does not make sense. I am not sure if call command is the best one to use.
I have never used P.S. before. I can try to formulate the same thing in Python (I know S.O. users tend to ask for "What have you tried so far"). Well, at this point I am VERY slow at writing anything in Power Shell language.
Please help.
First of all: call will be of no use here as you are apparently writing a batch file and PowerShell scripts have no association to run them by default. call is for batch files or subroutines.
Secondly, any PowerShell script you call from a batch file cannot change environment variables of the caller's environment. That's a fundamental property of how processes behave and since you are calling another process, this is never going to work.
I'm not so sure why you are even using a batch file here in the first place if you have PowerShell. You might just as well solve this in PowerShell completely.
However, what I get from your problem is that the best way to resolve this is probably the following: Create two batch files that each set the PATH appropriately. You can probably leave out both the MSSQL and Sybase paths from your usual PATH and add them solely in the batch files. Then create shortcuts to
cmd /k set_mssql_path.cmd
and
cmd /k set_sybase_path.cmd
each of which now is a shortcut to a shell to work with the appropriate database's tools. This is how the Visual Studio Command Prompt works and it's probably the cleanest solution you have. You can use the color and prompt commands in those batches to make the two different shells distinct so you always know what environment you have. For example the following two lines will color the console white on blue and set a prompt indicating MSSQL:
color 1f
prompt MSSQL$S$P$G
This can be quite handy, actually.
Generally, trying to rearrange the PATH environment variable isn't exactly easy. While you could trivially split at a ; this will fail for paths that itself contain a semicolon (and which need to be quoted then). Even in PowerShell this will take a while to get right so I think creating shortcuts specific to the tools is probably the nicest way to deal with this.

What's the difference in Windows program invocation?

I have a program on a Windows XP computer on another continent. If I start it by double-clicking on an associated file, so that it runs the program according to the file-type association, it crashes at a certain point. If I start it by dragging an associated file to the program icon, it works fine. If I double-click on the icon and drag the associated file to the window, it works fine.
The guy on site assures me that he's triple-checked the file-type association, and it should be correct.
Assuming that the icon points to the same executable as the registry, what differences would there be in starting the program in these two different ways?
EDIT: In response to a comment, the machine I'm having problems on is running in Japanese, while my normal machine is US English.
One possible difference is the initial working directory: if you drag a file onto the executable, the initial working directory is set to the directory containing the executable, whereas if you double click the file, the initial working directory is set to some default value independent of where the file or executable is located.
If you want to get consistent behavior in all cases, you can use SetCurrentDirectory() to set the current working directory to whatever you want; I recommend the directory containing the executable, which can be found by calling GetModuleFileName(NULL, ...) and stripping off the executable name, or by examining argv[0] inside main().
When you double click the file, the program is run, and (usually) the name of the file that you double click, is passed in to the program as a command line argument.
When you are dragging onto the window, the program is already running.
The difference is obviously in the startup process that the program has. Is this software written in-house? Perhaps check how it handles starting up, and make sure that all appropriate code paths are still executed when there is a file in the command line arguments.
If you can't check the program code, or how it behaves at startup, about the only thing to check in the registry, and possibly change, is how the filename is passed in. Usually they are passed in inside talking marks, so that the path to the file can have spaces and not confuse the program. Something to try would be to make sure the association uses talking marks on the argument, or if it already does, try it without. Perhaps the program isn't handling the talking marks correctly.