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SSI Conditional Expressions - Flow Control Elements

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Introduction

SSI allows conditional processing and provides a number of elements for this purpose.

The basic flow control elements are:

The #IF element works like an IF statement in programming. The test condition is evaluated and if the result is true then the text/lines following the IF statement is returned in the output until either on #ELIF, #ELSE or #END element is reached.

The #ELIF and #ELSE elements are used to output text/lines if the original #IF statement was false. If #ELIF is parsed the SSI will continue until either an #ELSE or #END element is reached, and if an #ELSE statement is parsed the SSI will continue until an #END element is reached.

The #END element closes the #IF element and must always be present or an error will likely occur.

The test_condition from the flow control code above is one of the following:

string1	If string NOT empty result is true
string1=string2	If string1 is equal to string2 result is true
string1!=string2	If string1 is NOT equal to string2 result is true
string1<string2	If string1 is less than string2 result is true
string1>string2	If string1 is greater than string2 result is true
string1>=string2	If string1 greater than or equal to string2 result is true
(test_condition)	If test_condition TRUE result is true
!test_condition	If test_condition FALSE result is true
test_condition1 && test_condition2	If test_condition1 AND test_condition2 are true result is true
test_condition1 \|\| test_condition2	If test_condition1 OR test_condition2 are true result is true

"=" and "!=" bind more tightly than "&&" and "||". "!" binds most tightly.

Anything that is not recognisable as a variable or an operator is treated as a string. To ensure your variable is treated as a variable you should use the format ${var_name}

If a string is written as /string/ it will be treated as a regular expression so to test something of the form /home/path you will need to use an escape sequence \"/home/path\".

Using the above information you can create quite complex tests. Here's a simple example to get you started:

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