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fflush

in my code there is a part like

scanf("%c",&sex);
fflush(stdin);      
printf("Enter the choice (C/W)");
scanf("%c",&choice);
fflush(stdin);      


it works on windows; but on fedora5 it doesnot clear the cache, what can i do for this?
0
btocakci
Asked:
btocakci
2 Solutions
 
PaulCaswellCommented:
Hi btocakci,

This is a common problem when porting. The original coder made use of 'undefined' behaviour.

I dont know a concrete, simple route around this, there are many alternatives. Essentially you need to consume without blocking, all data until a '\n' is read. If you can trust your users not to attempt buffer overflow hacking, this method is the most trivial:

char trash[256];

...

scanf("%c%s",&sex,trash);
printf("Enter the choice (C/W)");
scanf("%c%s",&choice, trash);

It is certainly not my favourite but it can be done with a fairly simple search/replace.

A second approach could be something like:

#define flusstdin while ( ... ) {<Insert your consumer here.>}

Again, a simple search/replace can fix all the abuse then.

Paul
0
 
ozoCommented:
fflush is only defined to work on output streams
some systems also define a non-standard fpurge that works on input streams
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fridomCommented:
The better answer wouild be
use a combination of fgets and sscanf


char buf[SOME_LIMIT]
char * pc = fgets(buf, sizeof(buf), stdin)
if (! pc)
 // error handling
...
int vals_read
int val;
vals_read = sscanf(buf, "%d", &val);
if (vals_read != 1)
  // error handling


Regards
Friedrich
0
 
karanaCommented:

please scanf from new line


scanf("%c",&sex);

printf("Enter the choice (C/W)");
printf("\n");
scanf("%c",&choice);

     
0
 
Razor2k5Commented:
Hi,

in order to have a more riguros approach use formatted read:

while (scanf("%d.%d.%d", &x, &y, &z) != 3) {
     while (getchar() != '\n'); /* line consuming
     printf("Try again...\n");
}
0

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