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man:strtol

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():
         _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 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" 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).
     +------------------------------+---------------+----------------+
     |Interface                     | Attribute     | Value          |
     +------------------------------+---------------+----------------+
     |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 deter-
     mine 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 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 charac-
         ters 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 4.16 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
     https://www.kernel.org/doc/man-pages/.

GNU 2017-09-15 STRTOL(3)

/data/webs/external/dokuwiki/data/pages/man/strtol.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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