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; 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, stopping at the first character which
       is not 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 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 integer value.

RETURN VALUE
       The  strtol()  function returns the result of the conversion, unless the value would underflow or overflow.  If an under-
       flow 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).

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 check-
       ing whether errno has a nonzero value after the call.

       In  locales  other than the "C" locale, other strings may also be accepted.  (For example, the thousands separator of the
       current locale may be supported.)

       BSD also has

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

       with completely analogous definition.  Depending on the wordsize of the current architecture, 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) argument 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 inter-
       face 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 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                                                        2007-07-26                                                  STRTOL(3)