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Powershell 101: IF .. Else

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 } )

Posted: 14 August 2006 14:12 by Paul Flaherty

Filed under: Flaphead, PowerShell

Comments

DBMwS said:

For more information, if you have PowerShell installed, you can check out PowerShell help files;

For the usages of "IF" statements;
get-help about_if

For generic Operator help;
get-help about_operator

For Comparison-specific operators;
get-help about_Comparison_operators

# August 15, 2006 17:47