Saliya's Blogs

Notes on Windows PowerShell

• Is bit slow and creepy ;) but better than command line
• Running as administrator helps you overcome many of the access denied situations
• PowerShell script files are simple text files with .ps1 extension
  • To run a script file,
    • Open a PowerShell instance (preferably as administrator) 
    • Type the path to .ps1 file and hit enter
  • If you get an error due to execution-policy is restricted, try

    set-executionpolicy remotesigned 

  • The above will ask for your permission. To avoid that and force use

     set-executionpolicy remotesigned -force

  • If you want this to be done across a Windows HPC cluster using clusrun command

    $nodes="node1,node2,..,noden"
    clusrun /nodes:$nodes powershell set-executionpolicy remotesigned -force

• To start a new process through a script - http://technet.microsoft.com/en-us/library/hh849848.aspx

  start-process command "options and args"

  
  
  • If you want it to be on the same window and wait for it to complete use

    start-process command "options and args" -NoNewWindow –Wait

• Invoke a command on a remote machine - http://technet.microsoft.com/en-us/library/hh849719.aspx

Invoke-Command -ComputerName $node -ScriptBlock {Start-Service MyService}


Handling variables


• Local variables

$x=10
$path="C:\users\dd"



• Command line parameters

$param0=$args[0]
$param1=$args[1]



• Environment (User/System) variables

$javaBin=$env:JAVA_HOME + "\bin"



• A better alternative – number 2 indicates system variable. Use number 1 for user variable

$javaHome=[Environment]::GetEnvironmentVariable("JAVA_HOME",2)



• Similarly to set a value – again number 2 is for system level.

[Environment]::SetEnvironmentVariable("Path","$tmp",2)

• String operations (few)


• Concatenation

$name="John"
$x="hello " + $name + "! How are you ?"



• Substring

$name.Substring(1) // "ohn"
$name.Substring(1,2) // "oh"



• StartsWith

$name.StartsWith("hello") // true



• IndexOf

$name.IndexOf("ohn") // 1



• Length

$name.Length // 4



• Join paths

$javaHome=$env:JAVA_HOME // e.g. "C:\Program Files\Java\jdk1.7.0_10"
$javaBinString=join-path -path $javaHome "bin" // e.g. "C:\Program Files\Java\jdk1.7.0_10\bin"



• Loops – a good tutorial at http://www.powershellpro.com/powershell-tutorial-introduction/logic-using-loops/


• For loop

for($i=1;$i -le 10; $i++) {
  //body
}

• -le is <=
• -lt is <
• -gt is >
• -eq is == in usual programming language notation


• Foreach loop

$jars=ls ($env:TWISTER_HOME + "\lib") *.jar
foreach ($jar in $jars) {
 $jar=$jar.DirectoryName + "\" +  $jar.Name
 $cp=$jar+";"+$cp
}

• .NET runtime directory

$([System.Runtime.InteropServices.RuntimeEnvironment]::GetRuntimeDirectory())

Study of Biological Sequence Structure: Clustering and Visualization