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RocketLink!--> Man page versions: OpenBSD FreeBSD RedHat Solaris Others

[ANSI C X3.159-1989]

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

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

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

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

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

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

     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.)

     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.

     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;

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

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

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

     Ignores the current locale.

OpenBSD 2.6                      June 25, 1992                               2

Source: OpenBSD 2.6 man pages. Copyright: Portions are copyrighted by BERKELEY
SOFTWARE DESIGN, INC., The Regents of the University of California, Massachusetts
Institute of Technology, Free Software Foundation, FreeBSD Inc., and others.

(Corrections, notes, and links courtesy of RocketAware.com)

[Detailed Topics]
FreeBSD Sources for strtol(3) functions
OpenBSD sources for strtol(3)

[Overview Topics]

Up to: String-Integer-String conversions - Converting strings to and from integers. ascii to long, long to ascii, etc.

RocketLink!--> Man page versions: OpenBSD FreeBSD RedHat Solaris Others

[ANSI C X3.159-1989]

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