while

Performs an iterative loop. An instruction or instruction block is executed repeatedly as long as the while expression is true. The test on the expression takes place before the execution of the statement.

while( expression ) statement... 

Example

The following example uses a while statement to loop through string str, searching for the first non-numeric character. The loop will continue until the expression is_digit becomes false i.e when the next character in str is not a digit but a non-numeric character.

    int is_digit = TRUE, i = 0;
    char * str = "1234567k89";
    int len = strlen(str);
    while (is_digit){
        if (i == len) {
            lr_output_message ("No letters found in string");
            return -1;
        }
        is_digit = isdigit(str[i++]);
    }
    lr_output_message ("The first letter appears in character %d of string", i);

Example: Output:
Action.c(18): The first letter appears in character 8 of string