The C Preprocessor
#elif' DirectiveOne common case of nested conditionals is used to check for more than two possible alternatives. For example, you might have
#if X == 1 ... #else /* X != 1 */ #if X == 2 ... #else /* X != 2 */ ... #endif /* X != 2 */ #endif /* X != 1 */
Another conditional directive, `#elif', allows this to be abbreviated
as follows:
#if X == 1 ... #elif X == 2 ... #else /* X != 2 and X != 1*/ ... #endif /* X != 2 and X != 1*/
`#elif' stands for ``else if''. Like `#else', it goes in the
middle of a `#if'-`#endif' pair and subdivides it; it does not
require a matching `#endif' of its own. Like `#if', the
`#elif' directive includes an expression to be tested.
The text following the `#elif' is processed only if the original
`#if'-condition failed and the `#elif' condition succeeds.
More than one `#elif' can go in the same `#if'-`#endif'
group. Then the text after each `#elif' is processed only if the
`#elif' condition succeeds after the original `#if' and any
previous `#elif' directives within it have failed. `#else' is
equivalent to `#elif 1', and `#else' is allowed after any
number of `#elif' directives, but `#elif' may not follow
`#else'.
The C Preprocessor
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