Manpage of STRTOUL
STRTOULSection: Linux Programmer's Manual (3)
NAMEstrtoul, strtoull, strtouq - convert a string to an unsigned long integer
#include <stdlib.h>unsigned long int strtoul(const char *nptr, char **endptr, int base);unsigned long long int strtoull(const char *nptr, char **endptr, int base);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
- _ISOC99_SOURCE ||
|| /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
DESCRIPTIONThe strtoul() function converts the initial part of the string in nptrto an unsigned long intvalue 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 aq+aq or aq-aq sign. If baseis zero or 16, the string may then include a "0x" prefix, and the number will be read in base 16; otherwise, a zero baseis taken as 10 (decimal) unless the character is aq0aq, in which case it is taken as 8 (octal).
The remainder of the string is converted to an unsigned long intvalue 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 aqAaq in either uppercase or lowercase represents 10, aqBaq represents 11, and so forth, with aqZaq representing 35.)
If endptris not NULL, strtoul() stores the address of the first invalid character in *endptr. If there were no digits at all, strtoul() stores the original value of nptrin *endptr(and returns 0). In particular, if *nptris not aq\0aq but **endptris aq\0aq on return, the entire string is valid.
RETURN VALUEThe strtoul() function returns either the result of the conversion or, if there was a leading minus sign, the negation of the result of the conversion represented as an unsigned value, unless the original (nonnegated) value would overflow; in the latter case, strtoul() returns ULONG_MAXand sets errnoto ERANGE. Precisely the same holds for strtoull() (with ULLONG_MAXinstead of ULONG_MAX).
- (not in C99) The given basecontains an unsupported value.
- The resulting value was out of range.
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
|strtoul(), strtoull(), strtouq()||Thread safety||MT-Safe locale|
CONFORMING TOstrtoul(): POSIX.1-2001, POSIX.1-2008, C89, C99 SVr4.
NOTESSince strtoul() can legitimately return 0 or ULONG_MAX(ULLONG_MAXfor strtoull()) on both success and failure, the calling program should set errnoto 0 before the call, and then determine if an error occurred by checking whether errnohas a nonzero value after the call.
In locales other than the "C" locale, other strings may be accepted. (For example, the thousands separator of the current locale may be supported.)
BSD also has
u_quad_t strtouq(const char *nptr, char **endptr, int base);with completely analogous definition. Depending on the wordsize of the current architecture, this may be equivalent to strtoull() or to strtoul().
EXAMPLESee the example on the strtol(3) manual page; the use of the functions described in this manual page is similar.
SEE ALSOa64l(3), atof(3), atoi(3), atol(3), strtod(3), strtol(3)
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