strtol(S)

strtol, strtoll, strtoul, strtoull, atol, atoll, atoi -- convert string to integer

Synopsis

   #include <stdlib.h>
   
   long strtol (const char str, char ptr, int base);
   

   long long strtoll (const char str, char ptr, int base);
   

   unsigned long strtoul (const char str, char ptr, int base);
   

   unsigned long long strtoull (const char str, char ptr, int base);
   

   int atoi (const char str);
   

   long atol (const char str);
   

   long long atoll (const char str);

Description

strtol returns as a long integer the value represented by the character string pointed to by str. The string is scanned up to the first character inconsistent with the base. Leading ``white-space'' characters [as defined by isspace in ctype(S)] are ignored.

If the value of ptr is not (char )NULL, a pointer to the character terminating the scan is returned in the location pointed to by ptr. If no integer can be formed, that location is set to str, and zero is returned.

If base is between 2 and 36, inclusive, it is used as the base for conversion. After an optional leading sign, leading zeros are ignored, and ``0x'' or ``0X'' is ignored if base is 16. A leading 0b or 0B is ignored if base is 2.

If base is zero, the string itself determines the base as follows: After an optional leading sign a leading zero indicates octal conversion, a leading ``0x'' or ``0X'' hexadecimal conversion, and a leading ``0b'' or ``0B'' binary conversion. Otherwise, decimal conversion is used.

Truncation from long to int can, of course, take place upon assignment or by an explicit cast.

If the value represented by str would cause overflow, LONG_MAX or LONG_MIN is returned (according to the sign of the value), and errno is set to the value, ERANGE.

strtoul is similar to strtol except that strtoul returns as an unsigned long integer the value represented by str. If the value represented by str would cause overflow, ULONG_MAX is returned, and errno is set to the value, ERANGE.

The strtoll and strtoull routines are similar, except that the return value is long long or unsigned long long, respectively.

Except for behavior on error, atol(str) is equivalent to:

   strtol(str, (char )NULL, 10)

Except for behavior on error, atoll(str) is equivalent to:

   strtoll(str, (char )NULL, 10)

Except for behavior on error, atoi(str) is equivalent to:

   (int) strtol(str, (char )NULL, 10)

Return values

If strtol is given a base greater than 36 or less than 2, it returns 0 and sets errno to EINVAL.

References

ctype(S), fscanf(S), strtod(S)

Notices

strtol no longer accepts values greater than LONG_MAX as valid input. Use strtoul instead.