System Programming

40K

Solutions

19K

Contributors

Kernel and system programming is the process of creating the software necessary for a computer or device to function and operate other programs. Some operating systems (such as Microsoft Windows) are proprietary, but others, such as the various Linux distributions, are open source.

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I've got a job creating the backend for a mobile app for a company. They will need me to do sysadmin tasks as well.

This app is useless if it can't connect to a server. I need to come up with a redundant setup, ideally over different providers (would like to use Linode and AWS).

I was wondering - what is this called, and how do I set it up? The most similar thing I have done is hosting a database on a separate server - both of those were in the same datacenter. I've read that you do not want the database to accept connections from public IP Addresses.

How do I set this up where there is redundancy over multiple data centers?
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Starting with Angular 5
LVL 12
Starting with Angular 5

Learn the essential features and functions of the popular JavaScript framework for building mobile, desktop and web applications.

Avoid Empty Catch Blocks
It’s a very bad habit to leave catch blocks empty, as when the exception is caught by the empty catch block, the program fails in silence, which makes debugging harder. Consider the following program which calculates sum of two numbers from command-line arguments:
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public class Sum {
    public static void main(String[] args) {
        int a = 0;
        int b = 0;
 
        try {
            a = Integer.parseInt(args[0]);
            b = Integer.parseInt(args[1]);
 
        } catch (NumberFormatException ex) {
        }
 
        int sum = a + b;
 
        System.out.println("Sum = " + sum);
    }
}
Note that the catch block is empty. If we run this program by the following command line:
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java Sum 123 456y
It will fail silently:
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Sum = 123

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when i tried above example i am getting different error as below istead of getting 123


public class Sum {
    public static void main(String[] args) {
        int a = 0;
        int b = 0;
 
        try {
            a = Integer.parseInt(args[0]);
            b = Integer.parseInt(args[1]);
 
        } catch (NumberFormatException ex) {
        }
 
        int sum = a + b;
 
        System.out.println("Sum = " + sum);
    }
}

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Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
      at Sum.main(Sum.java:7)

https://www.codejava.net/coding/10-java-core-best-practices-every-java-programmer-should-know

even below good catch block example also gives same error
public class SumFixed {
    public static void main(String[] args) {
        int a = 0;
        int b = 0;
 
        try {
            a = Integer.parseInt(args[0]);
            b = Integer.parseInt(args[1]);
 
        } catch (NumberFormatException ex) {
            System.out.println("One of the arguments are not number." +
                               "Program exits.");
            return;
        }
 
        int sum = a + b;
 
        System.out.println("Sum = " + sum);
    }
}

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Please advise
0
Hi Experts,

I have this question after resolving the following

https://www.experts-exchange.com/questions/29109077/How-to-concatenate-all-files-from-one-folder-into-one-ignoring-headers.html#a42623555

How can I modify the command to

1- Ignore all headers
2- include only files created in specific date range
3- include only files with specific names, like "*PatSched* and "*PatChanges*"

Thanks in advance.
0
What are the command can be used during debug windows memory dump to identify list of port and associated application. In normal windows we may use netstat -anob, but how to get to be execute in memory dump
0
Hi Experts,
I have the following batch file
@echo off
setlocal

set  tm=%time: =0%
set  tm=%tm::=%
set dt=%date:~10,4%%date:~4,2%%date:~7,2%

copy  C:\Users\bfuchs\Dropbox\Caspio\CaspioTables.zip  h:\CaspioTablesDaily\CaspioTables%dt%%tm:~0,4%.zip

copy  F:\Data\SkilledNursingVisitNotestbl.mdb  h:\AccessTablesDaily\Skilled_Nursing_Tables%dt%%tm:~0,4%.mdb

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Would like to have for the second file (the access file), to zip it into the destination, instead of just copying.

How can I accomplish that?

fyi- I have windows 7.

Thanks in advance.
0
Hi Experts,
the print screen key stopped working on my pc.
any suggestion?
preferably something that does not require restarting my pc...
thanks in advance.
fyi- I'm connected remotely thru gotomypc, however pass special keys to host is checked off.
0
#Requires -version 3.0
$WarningPreference="Continue"
#variables
$ScriptPath = $(Split-Path -Parent $MyInvocation.MyCommand.Definition)
#Log Timestamp
$logdate=Get-Date -Format ddMMyyyy_HHmmss
$Logfile = "E:\Logs\FileProcessing_$logdate.txt"
function LogWrite ([string]$logstring)
{  
   Add-content $Logfile -value $logstring
}
#Zip Files and move to backup folder
$sourcefolder="E:\Data"
$backupFolder="E:\Data\Backup"

I am want to build script which will do housekeeping of logs, archive folder and log activity if any file deleted then mention the file name deleted and similaly if log file deleted then log it what files deleted.
if no files to delete for day then mention in the log file no files to delete.
Backup folder archive data should have 7 years, more then 7 years should do rotation (older files to delete and new files to keep).
Backup folder 7 years files to keep, after that older archive files to delete and newer archive file to keep it.
Log folder 1 years logs to keep, after that older log files to delete and newer log file to keep it.
0
Hi Experts,
I have the following function trying to synchronize my local folder with a FTP folder.
Sub Example()
 
    Dim mySession As New Session
    
    ' Enable custom error handling
    On Error Resume Next
    
    Download mySession
    
    ' Query for errors
    If Err.Number <> 0 Then
        MsgBox "Error: " & Err.Description
 
        ' Clear the error
        
        Err.Clear
    End If
     
    ' Disconnect, clean up
    mySession.Dispose
     
    ' Restore default error handling
    On Error GoTo 0
    
End Sub
Public Sub Download(ByRef mySession As Session)
'Public Sub Download()
    ' Setup session options
    Dim mySessionOptions As New SessionOptions
    With mySessionOptions
        .Protocol = Protocol_Sftp
        .hostname = "sftp.MySite.com"
        .username = "MyUser"
        .password = "MyPWD"
        .SshHostKeyFingerprint = "ssh-rsa 2048 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx"
        
        
    End With
    
    ' Connect
    mySession.Open mySessionOptions
    
    ' Upload files
    Dim myTransferOptions As New TransferOptions
    myTransferOptions.TransferMode = TransferMode_Binary
    'myTransferOptions.ResumeSupport = TransferResumeSupportState.TransferResumeSupportState_Off
    myTransferOptions.ResumeSupport.State = TransferResumeSupportState_Off
     
    Dim transferResult As SynchronizationResult
    'Set transferResult = _
        mySession.GetFiles("/Outbox/*PatChanges*", "H:\FTP\", False, myTransferOptions)

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0
what are differences between eclipse short cuts F3 and Control +Shift+G
when to use which one?

Please advise
0
Hi Experts,

I have the function below that downloads files from a FTP server.

Option Explicit
 
Sub Example()
 
    Dim mySession As New Session
    
    ' Enable custom error handling
    On Error Resume Next
    
    Upload mySession
    
    ' Query for errors
    If Err.Number <> 0 Then
        MsgBox "Error: " & Err.Description
 
        ' Clear the error
        Err.Clear
    End If
     
    ' Disconnect, clean up
    mySession.Dispose
     
    ' Restore default error handling
    On Error GoTo 0
    
End Sub

Private Sub Download(ByRef mySession As Session)
 
    ' Setup session options
    Dim mySessionOptions As New SessionOptions
    With mySessionOptions
        .Protocol = Protocol_Sftp
        .HostName = "example.com"
        .UserName = "user"
        .Password = "mypassword"
        .SshHostKeyFingerprint = "ssh-rsa 2048 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx"
    End With
    
    ' Connect
    mySession.Open mySessionOptions
    
    ' Upload files
    Dim myTransferOptions As New TransferOptions
    myTransferOptions.TransferMode = TransferMode_Binary
     
    Dim transferResult As TransferOperationResult
    Set transferResult = _
        mySession.GetFiles("/home/user/*", "H:\FTP\", False, myTransferOptions)
     
    ' Throw on any error
    transferResult.Check
     
    ' Display results
    Dim transfer As TransferEventArgs
    For Each transfer In transferResult.Transfers
        MsgBox "Download of " & transfer.Filename & " 

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0
Exploring SQL Server 2016: Fundamentals
LVL 12
Exploring SQL Server 2016: Fundamentals

Learn the fundamentals of Microsoft SQL Server, a relational database management system that stores and retrieves data when requested by other software applications.

Hi Experts,

I have the script below do download all new files from my FTP server into my local PC.
However after running it for a while I get the attached error.

# Load WinSCP .NET assembly
Add-Type -Path "C:\Program Files (x86)\WinSCP\WinSCPnet.dll"

# Set up session options
$sessionOptions = New-Object WinSCP.SessionOptions -Property @{
    Protocol = [WinSCP.Protocol]::Sftp
    HostName = "sftp.MySite.com"
    UserName = "MyUserName"
    Password = "MyPWD"
    SshHostKeyFingerprint = "1234567890="
}

$session = New-Object WinSCP.Session

try
{
    # Connect
    $session.Open($sessionOptions)

    # Transfer files
    $sourcePath = "/Outbox/" # don't add *, will be added where necessary
    $destPath = "H:\FTP\"
    $destPathNew = "H:\FTP\Caspio\"

    $transferOptions = New-Object WinSCP.TransferOptions

    while($True)
    {
        try {
            # Get list of matching files in the directory
            $remoteFiles = $session.EnumerateRemoteFiles($sourcePath, "*.*", [WinSCP.EnumerationOptions]::None)

            # Any file matched?
            if ($remoteFiles.Count -gt 0) {
                foreach ($fileInfo in $remoteFiles) {
                    try {
                        Write-Host "Checking rules for the file " $fileInfo.Name
                        # check the filename for matching the mask
                        if ($fileInfo.Name -like "*PAT*.*" -or $fileInfo.Name -like "*Sch*.*" -or $fileInfo.Name -like "*Full*.*") {
                       

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0
Hi ,

I found this script it is useful saving my time.
i want help from experts...
after successful transfer it moving the file to archive..but every week the activity will go and chances for overwrite.
I want to have the dateandtime stamp to put while moving the files to archive..
can help to modify the code pls..

example
Localpathfile : E:\ABC\Zip_Source\testfile.xml.zip.p7
backupPath = "E:\ABC\Backup\testfile.xml.zip.p7_DDMMYYYY_HHMMSS

Script from internet

# Upload Files to FTP and move source files to archive
param (
    $localPath = "E:\ABC\Zip_Source\*.p7",
    $remotePath = "/home/user/",
    $backupPath = "E:\ABC\Backup\"
)
 
try
{
    # Load WinSCP .NET assembly
    Add-Type -Path "WinSCPnet.dll"
 
    # Setup session options
    $sessionOptions = New-Object WinSCP.SessionOptions -Property @{
        Protocol = [WinSCP.Protocol]::Sftp
        HostName = "example.com"
        UserName = "user"
        Password = "mypassword"
        SshHostKeyFingerprint = "ssh-rsa 2048 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx"
    }
 
    $session = New-Object WinSCP.Session
 
    try
    {
        # Connect
        $session.Open($sessionOptions)
 
        # Upload files, collect results
        $transferResult = $session.PutFiles($localPath, $remotePath)
 
        # Iterate over every transfer
        foreach ($transfer in $transferResult.Transfers)
        {
            # Success or error?
            if ($transfer.Error …
0
i have multiple files to encrypt using slift software.
I have the manual steps to encrypt but need help for encrypting it.
I have restriction not to store any password in the scripts hence it required password to be encrypted.
command is
slift.exe /e "sourcedirectory" /pfx "privatekeyfile.pfx" password /cer "partnerpublickey.cer"
can help how to script in powershell.
0
Hi Experts,

I have the following script that

1- downloads from a FTP site all new files to a local folder
2- Copy all downloaded files to another local folder.

However I see that 2nd step is not working properly, it downloads/copies all files again to the 2nd folder, not only the new files.
Can someone help me fix that?

# Load WinSCP .NET assembly
Add-Type -Path "C:\Program Files (x86)\WinSCP\WinSCPnet.dll"

# Set up session options
$sessionOptions = New-Object WinSCP.SessionOptions -Property @{
    Protocol = [WinSCP.Protocol]::Sftp
    HostName = "sftp.MySite.com"
    UserName = "MyUserName"
    Password = "MyPWD"
    SshHostKeyFingerprint = "1234567890="
}

$session = New-Object WinSCP.Session

try
{
    # Connect
    $session.Open($sessionOptions)

    # Transfer files
    $remotePath = "H:\FTP\*"
    
    $sourcePath = "/Outbox/*"
    $destPath = "H:\FTP\"
    $destPathNew = "H:\FTP\Caspio\"

    $transferOptions = New-Object WinSCP.TransferOptions

    $transferOptions.FileMask = "*PAT*.*;*Sch*.*|*Full*.*"

    while($True)
    {
         try
        {
            $transferResult = $session.GetFiles($sourcePath, $destPath, $False, $transferOptions)
            $transferResult.Check()
        }
        finally
        {
 	        foreach ($transfer in $transferResult.Transfers)
                {
                   $session.GetFiles($transfer.FileName, $destPathNew, $False, $transferOptions)
                    Write-Host "Download of 

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0
I have an application which implements a state machine based on StateForge (StateBuilderCpp) generator. A state machine is defined as asynchronous and uses boost in the generated code:

<settings asynchronous="true" library="boost">

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Actions (implemented methods) are very fast but are called frequently - events are triggered with 10ms intervals. State machine uses boost ioservice.

I run the application on a single core atom processor. Generally that pc is strongly utilized by others applications and I have noticed that sometimes when a cpu has a high iowait a dozen or so events are queued. Is it coincidence ? How to explains such behaviour ?
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exception java.net.MalformedURLException is never thrown in body of corresponding try statement
exception java.io.IOException is never thrown in body of corresponding try statement

i am getting above compilaion error in one of my facade manager class.

i wonder what that means

if i do not throw it but still catch that should be ok right right?
why i get compilation error

Please advise
0
Hi Experts,

The script below connects to a FTP site and downloads all newest files to a local folder in my pc.

How can I change this script to include only files  either with wording "PAT" or "Sched"?
However if file name contains word "Full" it should not be included.

# Load WinSCP .NET assembly
Add-Type -Path "C:\Program Files (x86)\WinSCP\WinSCPnet.dll"

# Set up session options
$sessionOptions = New-Object WinSCP.SessionOptions -Property @{
    Protocol = [WinSCP.Protocol]::Sftp
    HostName = "sftp.MySite.com"
    UserName = "MyUserName"
    Password = "MyPWD"
    SshHostKeyFingerprint = "1234567890="
}

$session = New-Object WinSCP.Session

try
{
    # Connect
    $session.Open($sessionOptions)

    # Transfer files
    $remotePath = "H:\FTP\*"
    
    $sourcePath = "/Outbox/*"
    $destPath = "H:\FTP\"
    $destPathNew = "H:\FTP\Caspio\"


    $transferOptions = New-Object WinSCP.TransferOptions
    while($True)
    {
 
        try
        {
     
            $transferResult = $session.GetFiles($sourcePath, $destPath, $False, $transferOptions)
            $transferResult.Check()
        }
        finally
        {
 	        foreach ($transfer in $transferResult.Transfers)
                {
                   $session.GetFiles($transfer.FileName, $destPathNew, $False, $transferOptions)
          
                    Write-Host "Download of $($transfer.FileName) succeeded"
                }
                $destPathNew1
        }
    }
    Write-Host 

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0
Hi Experts,
I have a script (.ps1) that would like to run it every 15 minutes.
When I right click and select run with powershell it runs.
However when trying to run this thru the windows task scheduler it says running, but nothing actually happens.
Perhaps I need a way to indicate it should run with PowerShell?
0
FlightsDestination.valueOf("price")


i was wondering how valueOf() method there on a custom objet
i thought it is just method on String class
https://study.com/academy/lesson/how-to-convert-int-to-string-in-java-valueof-method.html

does take string as input parameter like below
FlightsDestination.valueOf("price")

or
FlightsDestination.valueOf(price)

or

FlightsDestination.valueOf("400")

or
FlightsDestination.valueOf(400)



please advise
0
Exploring ASP.NET Core: Fundamentals
LVL 12
Exploring ASP.NET Core: Fundamentals

Learn to build web apps and services, IoT apps, and mobile backends by covering the fundamentals of ASP.NET Core and  exploring the core foundations for app libraries.

restfu get and post example


https://www.mkyong.com/webservices/jax-rs/restfull-java-client-with-java-net-url/
i am trying above example in eclipse.

I am not sure what all jars needed and what set up is needed to see that outputs

Please advise
0
object aid

when i try to add object aid uml plugin worked on one laptop

other laptop
when i gave the name

Name as Object Aid UML Explorer
Location http://objectaid.com/update/current

from eclipse-->help->install new softwares


getting below error

Unable to read repository at http://objectaid.com/update/current/content.xml.
Unable to read repository at http://objectaid.com/update/current/content.xml.
Malformed reply from SOCKS server


please advise
0
when we go to eclipse market place vs when we go
install new software option under eclise-->help

please advise
0
objectaid ul plugin now working

i went to eclipse -->help--->install new software

then i put url
http://www.objectaid.net/update
it brings windwo with saying
Add Repository
with 3 text boxes
Name
Location
not sure what to give above text boxes
after some times says
it says coulld find
http://www.objectaid.net/update

please advise
0
Hi All,

I am looking for a free open source POS system with no licensing which i can customise myself and use.

Anyone has any recommendations?
0
Hi Experts,
I have this question after solving the following..
https://www.experts-exchange.com/questions/29108803/Script-to-read-all-files-of-specific-folder.html#acceptAnswerByMember
In that question I got a script how to count all records of files in one folder.
However now I need to know from that count how many are under one specific category.
Therefore I thought the best way would be to concatenate all files into one, just ignoring the headers.
And from there I will link to MS Access and get the results from a query.
Anyone has either a script for that or another way to accomplish the task?
Thanks in advance.
0

System Programming

40K

Solutions

19K

Contributors

Kernel and system programming is the process of creating the software necessary for a computer or device to function and operate other programs. Some operating systems (such as Microsoft Windows) are proprietary, but others, such as the various Linux distributions, are open source.