NAME

strtol, strtoll, strtoimax, strtoq - convert string value to a long, long long, intmax_t or quad_t integer

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS



long int strtol(const char * restrict nptr, char ** restrict endptr, int base)

long long int strtoll(const char * restrict nptr, char ** restrict endptr, int base)



intmax_t strtoimax(const char * restrict nptr, char ** restrict endptr, int base)



quad_t strtoq(const char * restrict nptr, char ** restrict endptr, int base)

DESCRIPTION

The strtol() function converts the string in nptr to a long int value. The strtoll() function converts the string in nptr to a long long int value. The strtoimax() function converts the string in nptr to an intmax_t value. The strtoq() function converts the string in nptr to a quad_t value. The conversion is done according to the given base, which must be between 2 and 36 inclusive, or be the special value 0.

The string may begin with an arbitrary amount of white space (as determined by isspace(3)) followed by a single optional `+' or `-' sign. If base is zero or 16, the string may then include a `0x' prefix, and the number will be read in base 16; otherwise, a zero base is taken as 10 (decimal) unless the next character is `0', in which case it is taken as 8 (octal).

The remainder of the string is converted to a long value in the obvious manner, stopping at the first character which is not a valid digit in the given base. (In bases above 10, the letter `A' in either upper or lower case represents 10, `B' represents 11, and so forth, with `Z' representing 35.)

If endptr is non nil, strtol() stores the address of the first invalid character in *endptr. If there were no digits at all, however, strtol() stores the original value of nptr in *endptr. (Thus, if *nptr is not `\0' but **endptr is `\0' on return, the entire string was valid.)

RETURN VALUES

The strtol() function returns the result of the conversion, unless the value would underflow or overflow. If an underflow occurs, strtol() returns LONG_MIN, strtoll() returns LLONG_MIN, and strtoimax() returns INTMAX_MIN. If an overflow occurs, strtol() returns LONG_MAX, strtoll() returns LLONG_MAX, and strtoimax() returns INTMAX_MAX. In these cases, errno is set to ERANGE.

EXAMPLES

Ensuring that a string is a valid number (i.e., in range and containing no trailing characters) requires clearing errno beforehand explicitly since errno is not changed on a successful call to strtol(), and the return value of strtol() cannot be used unambiguously to signal an error:
char *ep;
long lval;
        

...

errno = 0; lval = strtol(buf, &ep, 10); if (buf[0] == '\0' || *ep != '\0') goto not_a_number; if (errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN)) goto out_of_range;

This example will accept ``12'' but not ``12foo'' or ``12\n''. If trailing whitespace is acceptable, further checks must be done on *ep; alternately, use sscanf(3).

If strtol() is being used instead of atoi(3), error checking is further complicated because the desired return value is an int rather than a long; however, on some architectures integers and long integers are the same size. Thus the following is necessary:

char *ep;
int ival;
long lval;
        

...

errno = 0; lval = strtol(buf, &ep, 10); if (buf[0] == '\0' || *ep != '\0') goto not_a_number; if ((errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN)) || (lval > INT_MAX || lval < INT_MIN)) goto out_of_range; ival = lval;

ERRORS

[ERANGE]
The given string was out of range; the value converted has been clamped.

SEE ALSO

atof(3), atoi(3), atol(3), atoll(3), strtod(3), strtoul(3), strtoull(3), strtoumax(3)

STANDARDS

The strtol() function conforms to ANSI X3.159-1989 (``ANSI C89'') . The strtoll() and strtoimax() functions conform to ISO/IEC 9899:1999 (``ISO C99'') .

BUGS

Ignores the current locale.