Programming in C

480 Appendix B The Standard C Library
In the descriptions that follow, s is a pointer to a null-terminated string, end is a pointer
to a character pointer, and base is an int.
All routines skip leading whitespace characters in the string and stop their scan upon
encountering a character that is invalid for the type of value being converted.
double atof (s)
Converts the string pointed to by s into a floating-point number, returning the result.
int atoi (s)
Converts the string pointed to by s into an int,returning the result.
int atol (s)
Converts the string pointed to by s into a long int,returning the result.
int atoll (s)
Converts the string pointed to by s into a long long int,returning the result.
double strtod (s, end)
Converts s to double,returning the result. A pointer to the character that terminated
the scan is stored inside the character pointer pointed to by end,provided end is not a
null pointer.
As an example, the code
#include
...
char buffer[] = " 123.456xyz", *end;
double value;
...
value = strtod (buffer, &end);
has the effect of storing the value 123.456 inside value.The character pointer variable
end is set by strtod to point to the character in buffer that terminated the
scan. In this case, it is set pointing to the character 'x'.
float strtof (s, end)
Is like strtod, except converts its argument to float.
long int strtol (s, end, base)
Converts s to long int,returning the result. base is an integer base number between
2 and 36, inclusive.The integer is interpreted according to the specified base. If base
is 0, the integer can be expressed in either base 10, octal (leading 0), or hexadecimal
(leading 0x or 0X). If base is 16, the value can optionally be preceded by a leading 0x
or 0X.