About Switch
Short description
Explains how to use a switch to handle multiple If
statements.
Long description
To check a condition in a script or function, use an If
statement. The If
statement can check many types of conditions, including the value of variables
and the properties of objects.
To check multiple conditions, use a Switch
statement. The Switch
statement
is equivalent to a series of If
statements, but it is simpler. The Switch
statement lists each condition and an optional action. If a condition obtains,
the action is performed.
The Switch
statement can use the $_
and $switch
automatic variables. For
more information, see
about_Automatic_Variables.
A basic Switch
statement has the following format:
Switch (<test-value>)
{
<condition> {<action>}
<condition> {<action>}
}
For example, the following Switch
statement compares the test value, 3, to
each of the conditions. When the test value matches the condition, the action
is performed.
switch (3)
{
1 {"It is one."}
2 {"It is two."}
3 {"It is three."}
4 {"It is four."}
}
It is three.
In this simple example, the value is compared to each condition in the list,
even though there is a match for the value 3. The following Switch
statement
has two conditions for a value of 3. It demonstrates that, by default, all
conditions are tested.
switch (3)
{
1 {"It is one."}
2 {"It is two."}
3 {"It is three."}
4 {"It is four."}
3 {"Three again."}
}
It is three.
Three again.
To direct the Switch
to stop comparing after a match, use the Break
statement. The Break
statement terminates the Switch
statement.
switch (3)
{
1 {"It is one."}
2 {"It is two."}
3 {"It is three."; Break}
4 {"It is four."}
3 {"Three again."}
}
It is three.
If the test value is a collection, such as an array, each item in the collection is evaluated in the order in which it appears. The following examples evaluates 4 and then 2.
switch (4, 2)
{
1 {"It is one." }
2 {"It is two." }
3 {"It is three." }
4 {"It is four." }
3 {"Three again."}
}
It is four.
It is two.
Any Break
statements apply to the collection, not to each value, as shown
in the following example. The Switch
statement is terminated by the Break
statement in the condition of value 4.
switch (4, 2)
{
1 {"It is one."; Break}
2 {"It is two." ; Break }
3 {"It is three." ; Break }
4 {"It is four." ; Break }
3 {"Three again."}
}
It is four.
Syntax
The complete Switch
statement syntax is as follows:
switch [-regex|-wildcard|-exact][-casesensitive] (<value>)
{
"string"|number|variable|{ expression } { statementlist }
default { statementlist }
}
or
switch [-regex|-wildcard|-exact][-casesensitive] -file filename
{
"string"|number|variable|{ expression } { statementlist }
default { statementlist }
}
If no parameters are used, Switch
behaves the same as using the Exact
parameter. It performs a case-insensitive match for the value. If the value is
a collection, each element is evaluated in the order in which it appears.
The Switch
statement must include at least one condition statement.
The Default
clause is triggered when the value does not match any of the
conditions. It is equivalent to an Else
clause in an If
statement. Only one
Default
clause is permitted in each Switch
statement.
Switch
has the following parameters:
- Wildcard - Indicates that the condition is a wildcard string. If the match clause is not a string, the parameter is ignored. The comparison is case-insensitive.
- Exact - Indicates that the match clause, if it is a string, must match exactly. If the match clause is not a string, this parameter is ignored. The comparison is case-insensitive.
- CaseSensitive - Performs a case-sensitive match. If the match clause is not a string, this parameter is ignored.
- File- Takes input from a file rather than a value statement. If multiple
File parameters are included, only the last one is used. Each line of the
file is read and evaluated by the
Switch
statement. The comparison is case-insensitive. - Regex - Performs regular expression matching of the value to the
condition. If the match clause is not a string, this parameter is ignored.
The comparison is case-insensitive. The
$matches
automatic variable is available for use within the matching statement block.
Note
When specifying conflicting values, like Regex and Wildcard, the last parameter specified takes precedence, and all conflicting parameters are ignored. Multiple instances of parameters are also permitted. However, only the last parameter used is effective.
In this example, an object that's not a string or numerical data is passed to
the Switch
. The Switch
performs a string coercion on the object and
evaluates the outcome.
$test = @{
Test = 'test'
Test2 = 'test2'
}
$test.ToString()
switch -Exact ($test)
{
'System.Collections.Hashtable'
{
'Hashtable string coercion'
}
'test'
{
'Hashtable value'
}
}
System.Collections.Hashtable
Hashtable string coercion
In this example, there is no matching case so there is no output.
switch ("fourteen")
{
1 {"It is one."; Break}
2 {"It is two."; Break}
3 {"It is three."; Break}
4 {"It is four."; Break}
"fo*" {"That's too many."}
}
By adding the Default
clause, you can perform an action when no other
conditions succeed.
switch ("fourteen")
{
1 {"It is one."; Break}
2 {"It is two."; Break}
3 {"It is three."; Break}
4 {"It is four."; Break}
"fo*" {"That's too many."}
Default {
"No matches"
}
}
No matches
For the word "fourteen" to match a case you must use the -Wildcard
or
-Regex
parameter.
PS> switch -Wildcard ("fourteen")
{
1 {"It is one."; Break}
2 {"It is two."; Break}
3 {"It is three."; Break}
4 {"It is four."; Break}
"fo*" {"That's too many."}
}
That's too many.
The following example uses the -Regex
parameter.
$target = 'https://bing.com'
switch -Regex ($target)
{
'^ftp\://.*$' { "$_ is an ftp address"; Break }
'^\w+@\w+\.com|edu|org$' { "$_ is an email address"; Break }
'^(http[s]?)\://.*$' { "$_ is a web address that uses $($matches[1])"; Break }
}
https://bing.com is a web address that uses https
A Switch statement condition may be either:
- An expression whose value is compared to the input value
- A script block which should return
$true
if a condition is met.
The $_
automatic variable contains the value passed to the switch statement
and is available for evaluation and use within the scope of the condition
statements.
The action for each condition is independent of the actions in other conditions.
The following example demonstrates the use of script blocks as Switch
statement conditions.
switch ("Test")
{
{$_ -is [String]} {
"Found a string"
}
"Test" {
"This $_ executes as well"
}
}
Found a string
This Test executes as well
If the value matches multiple conditions, the action for each condition is
executed. To change this behavior, use the Break
or Continue
keywords.
The Break
keyword stops processing and exits the Switch
statement.
The Continue
keyword stops processing the current value, but continues
processing any subsequent values.
The following example processes an array of numbers and displays if they are
odd or even. Negative numbers are skipped with the Continue
keyword. If a
non-number is encountered, execution is terminated with the Break
keyword.
switch (1,4,-1,3,"Hello",2,1)
{
{$_ -lt 0} { Continue }
{$_ -isnot [Int32]} { Break }
{$_ % 2} {
"$_ is Odd"
}
{-not ($_ % 2)} {
"$_ is Even"
}
}
1 is Odd
4 is Even
3 is Odd