strtoul man page on OpenBSD

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

     strtoul, strtoull, strtoumax, strtouq - convert a string to an unsigned
     long, unsigned long long or uintmax_t integer

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

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

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

     #include <inttypes.h>

     strtoumax(const char *nptr, char **endptr, int base);

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

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

     The strtoul() function converts the string in nptr to an unsigned long
     value.  The strtoull() function converts the string in nptr to an
     unsigned long long value.	The strtoumax() function converts the string
     in nptr to a umaxint_t value.  The strtouq() function is a deprecated
     equivalent of strtoull() 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.
     If the string in nptr represents a negative number, it will be converted
     to its unsigned equivalent.  This behavior is consistent with what
     happens when a signed integer type is cast to its unsigned counterpart.

     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 an unsigned long value in the
     obvious manner, stopping at the end of the string or at the first
     character 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-null, 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.)

     The strtoul(), strtoull(), strtoumax() and strtouq() functions return
     either the result of the conversion or, if there was a leading minus
     sign, the negation of the result of the conversion, unless the original
     (non-negated) value would overflow.  If overflow occurs, strtoul()
     returns ULONG_MAX, strtoull() returns ULLONG_MAX, strtoumax() returns
     UINTMAX_MAX, strtouq() returns ULLONG_MAX and the global variable errno
     is set to ERANGE.	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.

     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

     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
     return value of strtoul() cannot be used unambiguously to signal an

	   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
     trailing whitespace is acceptable, further checks must be done on *ep;
     alternately, use sscanf(3).

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

     sscanf(3), strtol(3)

     The strtoul(), strtoull(), and strtoumax() functions conform to
     ANSI/ISO/IEC 9899-1999 (``ANSI C99'').  The strtouq() function is a BSD
     extension and is provided for backwards compatibility with legacy

     Ignores the current locale.

OpenBSD 4.9			 April 7, 2010			   OpenBSD 4.9

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