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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():
           _ISOC99_SOURCE
               || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE

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" or "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

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────────────┬───────────────┬────────────────┐
       │InterfaceAttributeValue          │
       ├──────────────────────────────┼───────────────┼────────────────┤
       │strtol(), strtoll(), strtoq() │ Thread safety │ MT-Safe locale │
       └──────────────────────────────┴───────────────┴────────────────┘

CONFORMING TO

       strtol(): POSIX.1-2001, POSIX.1-2008, C89, C99 SVr4, 4.3BSD.

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

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,  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 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
       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), strtoimax(3)

COLOPHON

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