STRTOL(3) AerieBSD 1.0 Refernce Manual STRTOL(3)

NAME

strtol — strtoll, strtoimax, strtoq, "convert string value to a long, long long or intmax_t integer"

SYNOPSIS

#include <limits.h>
#include <stdlib.h>

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

longlong strtoll(const char *nptr, char **endptr, int base);

#include <inttypes.h>

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

#include <sys/types.h>
#include <limits.h>
#include <stdlib.h>

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

DESCRIPTION

The strtol(); function converts the string in nptr to a long value. The strtoll(); function converts the string in nptr to a long long value. The strtoimax(); function converts the string in nptr to an intmax_t value. The strtoq(); function is a deprecated equivalent of strtoll(); and is provided for backwards compatibility with legacy programs. The conversion is done according to the given base, which must be a number between 2 and 36 inclusive or the special value 0.

The string may begin with an arbitrary amount of whitespace (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, long long, or intmax_t, 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-null, 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 "\e0" but **endptr is "\e0" on return, the entire string was valid.)

RETURN VALUES

The strtol();, strtoll();, strtoimax();, and strtoq(); functions return the result of the conversion, unless the value would underflow or overflow. If no conversion could be performed, 0 is returned; the global variable errno is also set to EINVAL, though this is not portable across all platforms. If overflow or underflow occurs, errno is set to ERANGE and the function return value is as follows:

Function underflow overflow
strtol(Ta Dv LONG_MIN Ta Dv LONG_MAX);
strtoll(Ta Dv LLONG_MIN Ta Dv LLONG_MAX);
strtoimax(Ta Dv INTMAX_MIN Ta Dv INTMAX_MAX);
strtoq(Ta Dv LLONG_MIN Ta Dv LLONG_MAX);

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] == '\e0' || *ep != '\e0')
	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\en”. 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] == '\e0' || *ep != '\e0')
     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), sscanf(3), strtod(3), strtonum(3), strtoul(3)

STANDARDS

The strtol();, strtoll();, and strtoimax(); functions conform to The strtoq(); function is a BSD extension and is provided for backwards compatibility with legacy programs.

BUGS

Ignores the current locale.

AerieBSD 1.0 Reference Manual August 26 2008 STRTOL(3)