int atoi ( const char* str );
(1)long atol ( const char* str );
(2)long long atoll( const char* str );
(3) (since C99)Interprets an integer value in a byte string pointed to by str. The implied radix is always 10.
Discards any whitespace characters until the first non-whitespace character is found, then takes as many characters as possible to form a valid integer number representation and converts them to an integer value. The valid integer value consists of the following parts:
If the value of the result cannot be represented, i.e. the converted value falls out of range of the corresponding return type, the behavior is undefined.
[edit] Parameters str - pointer to the null-terminated byte string to be interpreted [edit] Return valueInteger value corresponding to the contents of str on success.
If no conversion can be performed, â0â is returned.
[edit] NotesThe name stands for âASCII to integerâ.
[edit] Example#include <stdio.h>
#include <stdlib.h>
int main(void)
{
printf("%i\n", atoi(" -123junk"));
printf("%i\n", atoi(" +321dust"));
printf("%i\n", atoi("0"));
printf("%i\n", atoi("0042")); // treated as a decimal number with leading zeros
printf("%i\n", atoi("0x2A")); // only leading zero is converted discarding "x2A"
printf("%i\n", atoi("junk")); // no conversion can be performed
printf("%i\n", atoi("2147483648")); // UB: out of range of int
}
Possible output:
-123 321 0 42 0 0 -2147483648[edit] References
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