What quzah gave you will work, but if you don't understand what his code does, it won't help you in solving the problem in the future.

The construct
Code:
b ? "true" : "false"
is a conditional expression where if the value of b (which can be an arbitrary boolean expression) is true, the value of the construct is the expression following the question mark (in this case, a pointer to a nul terminated char array containing the string "true"), and if b is false the expression has the value of the expression following the colon (in this case, a pointer to a nul terminated char array containing the string "false"). Look up "conditional expression" in your C language reference.

Are you saying I need to write my own function to do this?
The answer to this is "no". You can simply use a conditional expression wherever you want to do the conversion of a boolean to a string. If you do it more than once, though, a function will be more code-space efficient. You could write your code as:
Code:
ShLogWrite("_CINSRCH", GbCEPSecurity ? "true" : "false");