Powershell 101: IF .. Else
Originally Posted here: http://blogs.flaphead.dns2go.com/archive/2006/08/14/3509.aspx
Okay as a beginner this took a bit of time to perfect so here goes. For some of you hardened programmers this might be a bit basic, but I had to start somewhere. My background is cmd and vbs files with some html chucked in, so this syntax is new to me
Simple IF, Else
$a = "Powershell"
IF ($a -eq "PowerShell")
{
"Statement is True"
}
ELSE
{
"Statement is False"
}
You can condence this to:
$a = "Powershell"
IF ($a -eq "PowerShell"){ "Statement is True"} ELSE { "Statement is False"}
Now if you want to check for a NULL then it gets fun
$b = “Hello”
IF ($b -eq $NULL)
{
"B is NULL"
}
ELSE
{
"B is NOT NULL"
}
So you have whole load of conditional statement like these:
| Operator | Definition |
| -lt | Less than |
| -le | Less than or equal to |
| -gt | Greater than |
| -ge | Greater than or equal to |
| -eq | Equal to. If the left hand side of the operator is an array and the right hand side is a scalar, the equivalent values of the left hand side will be returned |
| -ne | Not Equal to. If the left hand side of the operator is an array and the right hand side is a scalar, the not equivalent values of the left hand side will be returned |
| -contains | Determine elements in a group, this always returns Boolean $True or $False. |
| -notcontains | Determine excluded elements in a group, this always returns Boolean $True or $False. |
| -like | Like - uses wildcards for pattern matching |
| -notlike | Not Like - uses wildcards for pattern matching |
| -match | Match - uses regular expressions for pattern matching |
| -notmatch | Not Match - uses regular expressions for pattern matching |
| -band | Bitwise AND |
| -bor | Bitwise OR |
| -is | Is of Type |
| -isnot | Is not of Type |
These operators are the case-sensitive counterparts:
| Operator | Definition |
| -clt | Less than (case sensitive) |
| -cle | Less than or equal to (case sensitive) |
| -cgt | Greater than (case sensitive) |
| -cge | Greater than or equal to (case sensitive) |
| -ceq | Equal to (case sensitive) |
| -cne | Not Equal to (case sensitive) |
| -clike | Like (case sensitive) |
| -cnotlike | Not Like (case sensitive) |
| -ccontains | left hand side contains right hand side in a case sensitive manner |
| -cnotcontains | determine excluded elements in a group in a case sensitive manner |
| -cmatch | Match (case sensitive) |
| -cnotmatch | Not Match (case sensitive) |
Other operators: | Operator | Definition |
| + | Add |
| - | Subtract |
| * | Multiply |
| / | Divide |
| % | Modulo |
| -not | logical not |
| ! | logical not |
| -band | binary and |
| -bor | binary or |
| -bnot | binary not |
| -replace | Replace (e.g. "abcde" –replace "b","B") (case insensitive) |
| -ireplace | Case-insensitive replace (e.g. "abcde" –ireplace "B","3") |
| -creplace | Case-sensitive replace (e.g. "abcde" –creplace "B","3") |
| -and | AND (e.g. ($a -ge 5 -AND $a -le 15) ) |
| -or | OR (e.g. ($a –eq "A" –OR $a –eq "B") ) |
| -is | IS type (e.g. $a -is [int] ) |
| -isnot | IS not type (e.g. $a -isnot [int] ) |
| -as | convert to type (e.g. 1 -as [string] treats 1 as a string ) |
| .. | Range operator (e.g. foreach ($i in 1..10) {$i } ) |
| & | call operator (e.g. $a = "Get-ChildItem" &$a executes Get-ChildItem) |
| . (dot followed by a space) | call operator (e.g. $a = "Get-ChildItem" . $a executes Get-ChildItem in the current scope) |
| -F | Format operator (e.g. foreach ($p in Get-Process) { "{0,-15} has {1,6} handles" –F $p.processname,$p.Handlecount } ) |
