strtol(3)



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 deter-
       mined 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
       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 integer value.

RETURN VALUE
       The strtol() function returns the result of the conversion, unless  the
       value  would  underflow  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 appli-
       cations, 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 str-
       toll() 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  deter-
       mine 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  architecture,  this  may be equivalent to strtoll() or to str-
       tol().

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 interface than strtol().)  Some examples of the results pro-
       duced 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 3.71 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)

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