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

NAME
     strtol, strtoq - convert string value to a long or quad_t integer



SYNOPSIS
     #include <stdlib.h>
     #include <limits.h>

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


     #include <sys/types.h>
     #include <stdlib.h>
     #include <limits.h>

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

DESCRIPTION
     The strtol() function converts the string in nptr to a long value.  The
     strtoq() function converts the string in nptr to a quad_t value.  The
     conversion is done according to the given base, which must be a number
     between 2 and 36 inclusive or 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 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' represent-
     ing 35.)

     If endptr is non nil, strtol() stores the address of the first invalid
     character in *endptr. If there were no digits at all, however, strtol()
     stores the original value of nptr in *endptr. (Thus, if *nptr is not `\0'
     but **endptr is `\0' on return, the entire string was valid.)

RETURN VALUES
     The strtol() function returns the result of the conversion, unless the
     value would underflow or overflow.  If an underflow occurs, strtol() re-
     turns LONG_MIN. If an overflow occurs, strtol() returns LONG_MAX. In both
     cases, errno is set to ERANGE.

EXAMPLES
     Ensuring that a string is a valid number (i.e., in range and containing
     no trailing characters) requires clearing errno beforehand explicitly
     since errno is not changed on a successful call to strtol(), and the re-
     turn value of strtol() cannot be used unambiguously to signal an error:

           char *ep;
           long lval;

           ...

           errno = 0;
           lval = strtol(buf, &ep, 10);
           if (buf[0] == '\0' || *ep != '\0')
                   goto not_a_number;
           if (errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN))
                   goto out_of_range;

     This example will accept ``12'' but not ``12foo'' or ``12\n''. If trail-
     ing whitespace is acceptable, further checks must be done on *ep; alter-
     nately, use sscanf(3).

     If strtol() is being used instead of atoi(3),  error checking is further
     complicated because the desired return value is an int rather than a
     long; however, on some architectures integers and long integers are the
     same size.  Thus the following is necessary:

           char *ep;
           int ival;
           long lval;

           ...

           errno = 0;
           lval = strtol(buf, &ep, 10);
           if (buf[0] == '\0' || *ep != '\0')
                goto not_a_number;
           if ((errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN)) ||
               (lval > INT_MAX || lval < INT_MIN))
                goto out_of_range;
           ival = lval;

ERRORS
     [ERANGE]      The given string was out of range; the value converted has
                   been clamped.

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

STANDARDS
     The strtol() function conforms to ANSI X3.159-1989 (``ANSI C'').

BUGS
     Ignores the current locale.

OpenBSD 2.6                      June 25, 1992                               2