#include <stdlib.h> long int strtol(const char *str, char **end, int radix);
strtol converts a character string to a long integer. The
string is expected to contain the representation of an integer in base
radix. Base radix can contain an integer between 2 and 36; if it
is larger than 10, letters 'a' through 'z' (either case) are interpreted as
digits greater than 10. If radix is 16, a leading 0x may be present in
the string, but it is ignored. Initial white space characters are always ignored.
If radix is 0, the base is determined by the initial characters of
the string (after leading white space and an optional sign). That is,
if the string begins with 0x or 0X, the base is assumed to be 16; if it
begins with 0, it is assumed to be 8; otherwise, it is assumed to be 10.
If the end value is not NULL, *end is modified to address
the first character of the string that is not a valid base radix
digit. However, if no initial segment of the string can be interpreted
as an integer of appropriate base, str is assigned to *end.
strtol returns the integer value represented by the character
string, up to the first unrecognized character. If no initial segment
of the string can be interpreted as an integer of appropriate base,
0L is returned.
long,
errno is set to ERANGE and either LONG_MAX (2**31)-1 or
LONG_MIN (-2**31) is returned, depending on the sign of
the value.
#include <stdlib.h>
#include <ctype.h>
#include <stdio.h>
long int hextol(char *);
static int failed;
main()
{
char *string;
char input[20];
long output;
puts("Enter a hex string to convert to long int:");
string = gets(input);
output = hextol(string);
if (!failed)
printf("The value of the string, printed in decimal, is: %ldn",
output);
}
long int hextol(char *hexstr)
{
long value;
char *stopchar; /* where strtol conversion stops */
/* Skip space characters. */
while(isspace(*hexstr)) ++hexstr;
/* Skip leading 0x. */
if (*hexstr == '0' && tolower(*(hexstr+1)) == 'x')
hexstr += 2;
/* refused signed hex value */
if (*hexstr == '+' || *hexstr == '-') {
puts("Unsigned hex only please");
failed = 1;
return -1L;
}
/* Convert hex to long. */
value = strtol(hexstr, &stopchar, 16);
/* Determine whether string is valid. */
if (stopchar == hexstr) {
printf("Invalid hex string: %sn", hexstr);
failed = 1;
}
/* Check for characters after digits. */
else if (*stopchar && !isspace(*stopchar))
printf("Extra characters after hex value ignored: %sn",
stopchar);
return value;
}
strtod, strtoul
Copyright (c) 1998 SAS Institute Inc. Cary, NC, USA. All rights reserved.