STRTOUL(3)                OpenBSD Programmer's Manual               STRTOUL(3)

NAME
     strtoul, strtouq - convert a string to an unsigned long or uquad_t



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

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


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

     u_quad_t
     strtouq(const char *nptr, char **endptr, int base);

DESCRIPTION
     The strtoul() function converts the string in nptr to an unsigned long
     value.  The strtouq() function converts the string in nptr to a u_quad_t
     value.  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 white space (as deter-
     mined 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 an unsigned long value in the
     obvious manner, stopping at the end of the string or at the first charac-
     ter that does not produce 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, strtoul() stores the address of the first invalid
     character in *endptr. If there were no digits at all, however, strtoul()
     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 strtoul() function returns the result of the conversion, unless the
     value would overflow, in which case ULONG_MAX is returned and errno is
     set to ERANGE. If there was a leading minus sign, strtoul() returns the
     (unsigned) negation of the absolute value of the number, unless the abso-
     lute value would overflow.  In this case, strtoul() returns ULONG_MAX and
     sets the global variable errno to ERANGE.

     There is no way to determine if strtoul() has processed a negative number
     (and returned an unsigned value) short of examining the string in nptr
     directly.

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 strtoul(), and the re-
     turn value of strtoul() cannot be used unambiguously to signal an error:

           char *ep;
           unsigned long ulval;

           ...

           errno = 0;
           ulval = strtoul(buf, &ep, 10);
           if (buf[0] == '\0' || *ep != '\0')
                   goto not_a_number;
           if (errno == ERANGE && ulval == ULONG_MAX)
                   goto out_of_range;

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

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

SEE ALSO
     sscanf(3),  strtol(3)

STANDARDS
     The strtoul() function conforms to ANSI X3.159-1989 (``ANSI C'').

BUGS
     Ignores the current locale.

OpenBSD 2.6                      June 25, 1992                               2