====== if/else/endif ======

The ''if'' operator switches execution of the script depending on the value of a boolean argument:
  * If the argument is true, control passes to the line following the ''if'' statement. 
  * If the argument is false, control passes to the line following the next ''else'' or ''endif'' statement.

The function of ''if'', ''else'' and ''endif'' are demonstrated below:

<code>
// create a new boolean value, and set it to true
bool b
set b true

// test value of 'b', and echo value to event log
if b
  echo "b is true!"
else
  echo "b is false!"
endif
</code>

The output of which is:

<file>
b is true!
</file>

===== Closure and nesting =====

Each ''if'' statement must be closed by a matching ''endif'' statement, and may contain one ''else'' statement. Chains of if/else statements must be nested (unlike C/C++), as shown below:

<code>
// create a new string value, and use it to compare in if/else chain
string s
set s "goodbye"

// test value of 's', and reply accordingly
if <zs:not <zs:strcmp s "hello">>
  echo "Hello to you too!"
else
  if <zs:not <zs:strcmp s "goodbye">> // note if is nested inside else
    echo "Farewell!"
  endif
endif
</code>

The output of which is:

<file>
Farewell!
</file>