int a;
scanf("%d",&a);
How can I ensure the code doesn't work if a non-digit character is given as input to the scanf() statement? [I need a solution that doesn't make me change the data type to char]
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1By reading the documentation for scanf and making use of the return value. Simple!enhzflep– enhzflep2013-06-24 06:33:54 +00:00Commented Jun 24, 2013 at 6:33
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Thanks! The return value did the job.amulous– amulous2013-06-24 06:40:47 +00:00Commented Jun 24, 2013 at 6:40
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3 Answers
If the first character is not a digit, then %d will fail to match, and a will not be assigned. The return value of scanf tells you how many items were assigned. If it's one, then clearly it was at least partially a valid number. If it's zero, that means it couldn't be parsed as a number, and you may want to signal an error.
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amulous
Thanks! Finally understood this.
The scanf return code will tell you how many items in your arg list were filled. This may still not be what you want: I think you'll find input "123four" will still return 1, with a=123.
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You can use a do while loop for validating input from user like:
int read,a;
do {
read = scanf("%c", &a);
}while(read != EOF && a != '\n'); //change validation here according to condition
