STRTOL(3)                           Linux Programmer's Manual                           STRTOL(3)



NAME
       strtol, strtoll, strtoq - convert a string to a long integer

SYNOPSIS
       #include <stdlib.h>

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

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

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       strtoll():
           _XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE ||
           _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION
       The strtol() function converts the initial part of the string in nptr to  a  long  integer
       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 a long int value in the obvious manner,  stop‐
       ping 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,  strtol()  stores the address of the first invalid character in
       *endptr.  If there were no digits at all, strtol() 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 strtoll() function works just like the strtol() function but returns a long long inte‐
       ger value.

RETURN VALUE
       The  strtol() function returns the result of the conversion, unless the value would under‐
       flow or overflow.  If an underflow occurs, strtol()  returns  LONG_MIN.   If  an  overflow
       occurs,  strtol() returns LONG_MAX.  In both cases, errno is set to ERANGE.  Precisely the
       same holds for strtoll() (with LLONG_MIN and LLONG_MAX instead of LONG_MIN and LONG_MAX).

ERRORS
       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).

ATTRIBUTES
   Multithreading (see pthreads(7))
       The  strtol(),  strtoll(),  and strtoq() functions are thread-safe with exceptions.  These
       functions can be safely used in multithreaded applications, as long as setlocale(3) is not
       called to change the locale during their execution.

CONFORMING TO
       strtol()  conforms  to  SVr4, 4.3BSD, C89, C99, and POSIX.1-2001, and strtoll() to C99 and
       POSIX.1-2001.

NOTES
       Since strtol() can legitimately return 0, LONG_MAX, or LONG_MIN  (LLONG_MAX  or  LLONG_MIN
       for  strtoll())  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.

       According  to POSIX.1-2001, in locales other than the "C" and "POSIX", these functions may
       accept other, implementation-defined numeric strings.

       BSD also has

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

       with completely analogous definition.  Depending on the wordsize of the current  architec‐
       ture, this may be equivalent to strtoll() or to strtol().

EXAMPLE
       The program shown below demonstrates the use of strtol().  The first command-line argument
       specifies a string from which strtol() should parse a number.  The second (optional) argu‐
       ment  specifies  the  base  to be used for the conversion.  (This argument is converted to
       numeric form using atoi(3), a function that performs no error checking and has  a  simpler
       interface  than  strtol().)  Some examples of the results produced by this program are the
       following:

           $ ./a.out 123
           strtol() returned 123
           $ ./a.out '    123'
           strtol() returned 123
           $ ./a.out 123abc
           strtol() returned 123
           Further characters after number: abc
           $ ./a.out 123abc 55
           strtol: Invalid argument
           $ ./a.out ''
           No digits were found
           $ ./a.out 4000000000
           strtol: Numerical result out of range

   Program source

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

       int
       main(int argc, char *argv[])
       {
           int base;
           char *endptr, *str;
           long val;

           if (argc < 2) {
               fprintf(stderr, "Usage: %s str [base]\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           str = argv[1];
           base = (argc > 2) ? atoi(argv[2]) : 10;

           errno = 0;    /* To distinguish success/failure after call */
           val = strtol(str, &endptr, base);

           /* Check for various possible errors */

           if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
                   || (errno != 0 && val == 0)) {
               perror("strtol");
               exit(EXIT_FAILURE);
           }

           if (endptr == str) {
               fprintf(stderr, "No digits were found\n");
               exit(EXIT_FAILURE);
           }

           /* If we got here, strtol() successfully parsed a number */

           printf("strtol() returned %ld\n", val);

           if (*endptr != '\0')        /* Not necessarily an error... */
               printf("Further characters after number: %s\n", endptr);

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       atof(3), atoi(3), atol(3), strtod(3), strtoul(3)

COLOPHON
       This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



GNU                                         2014-03-18                                  STRTOL(3)