On Sat, 5 Mar 2005 13:18:26 +0100 (CET), J. <[EMAIL PROTECTED]> wrote:
> On Sat, 5 Mar 2005, Rechberger Markus wrote:
>
> > Hey,
>
> Hey.. ;-)
>
> > regarding atoi:
> >
> > #include <stdio.h>
>
> #include <stdlib.h>
>
> > int main(){
> > printf("value: %d\n",atoi("nosegv123"));
> > return(0);
> > }
> > output:
> > value: 0
> >
> > this doesn't segfault
>
> Yes, - atoi in stdlib.h is actually strtol...
>
> But, the answer was about using atoi in combination with
> getopt(), maybe it was my lack of explanation sorry...
> Anyway, atoi(optarg) while there is no optarg will segfault...
for that case we have the doublepoint in optarg which says that it
needs an argument otherwise it would return for example:
./main: option requires an argument -- n
value=atoi(optarg)
if(value==0&&*optarg!='0'){
printf("invalid argument\n");
exit(1);
}
this doesn't check overflow/underflow strtol would probably be better
in that case.. the manpage explains this quite accurate..
Markus
> Then, you will always want to check for digits, since atoi
> can't determine the difference inbetween the argument `0'
> or "nosegv123" . atoi returns the same value for both, thus `0' .
>
> If your program checks something INT times and atoi returns `0'
> even on errorlike user input, the program will check `0' times..
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main(int argc, char *argv[]){
> char *str1 = "nosegv123";
> char *str2 = "0.012";
> char *str3 = "0";
> char *str4 = "-1";
>
> printf("str: %s - value: %d\n",str1, atoi(str1));
> printf("str: %s - value: %d\n",str2, atoi(str2));
> printf("str: %s - value: %d\n",str3, atoi(str3));
> printf("str: %s - value: %d\n",argv[1], atoi(argv[1]));
> printf("str: %s - value: %d\n",str4, atoi(str4));
> return(0);
> }
>
> > ctype only takes one variable as argument _not_ a string, he would
> > have to check every element of the array with isdigit.
>
> Yep.. But *pointers are quite cheap these days I hear.. ;-)
>
> Thnkx.. J.
>
> > > int isthisanint(char *str) {
> > > regex_t re;
> > > int retval = -1;
> > >
> > > setlocale(LC_ALL, "");
> > > if(regcomp(&re, "^([0-9]*)$", REG_EXTENDED) != 0) {
> > > fprintf(stderr, "%s: Error - Unable to compile regex", PACKAGE);
> > > return -1;
> > > }
> > >
> > > if(regexec(&re, str, 0, NULL, 0) != 0)
> > > retval = -1;
> > > else
> > > retval = atoi(str);
> > >
> > > /* or.. Like listed in the manual page */
> > > /* strtol(nptr, (char **)NULL, 10); */
> > >
> > > regfree(&re);
> > > return retval;
> > > }
>
> -
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