strtoul,  strtoull,  strtouq  -  convert  a  string to an unsigned long


   #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


   The strtoul() function converts the initial part of the string in  nptr
   to  an  unsigned long int value 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 an unsigned long int 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 uppercase or lowercase represents 10, 'B' represents 11, and  so
   forth, with 'Z' representing 35.)

   If  endptr  is  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 nptr in *endptr (and returns 0).
   In particular, if *nptr is not '\0' but **endptr is '\0' on return, the
   entire string is valid.

   The  strtoull()  function  works  just  like the strtoul() function but
   returns an unsigned long long int value.


   The 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_MAX and sets errno to ERANGE.  Precisely the  same  holds
   for strtoull() (with ULLONG_MAX instead of ULONG_MAX).


   EINVAL (not in C99) The given base contains an unsupported value.

   ERANGE The resulting value was out of range.

   The  implementation  may also set errno to EINVAL in case no conversion
   was performed (no digits seen, and 0 returned).


   For  an  explanation  of  the  terms  used   in   this   section,   see

   Interface                         Attribute      Value          
   strtoul(), strtoull(), strtouq()  Thread safety  MT-Safe locale 


   strtoul(): POSIX.1-2001, POSIX.1-2008, C89, C99 SVr4.

   strtoull(): POSIX.1-2001, POSIX.1-2008, C99.


   Since  strtoul() can legitimately return 0 or ULONG_MAX (ULLONG_MAX for
   strtoull()) on both success and failure, the calling program should set
   errno  to 0 before the call, and then determine if an error occurred by
   checking whether errno has 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

   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

   Negative values are considered valid input and are  silently  converted
   to the equivalent unsigned long int value.


   See  the example on the strtol(3) manual page; the use of the functions
   described in this manual page is similar.


   a64l(3), atof(3), atoi(3), atol(3), strtod(3), strtol(3)


   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.