Question about user input validaton

So I need to validate the input that the user enters. The user has to enter his name , and the program must check that the name's characters are from the alphabet , but the single quote ' and space can also be used.

No other symbols or punctuation must be used.

I know how to do all these validations , except the one where the single quote character has to be valid ad not assumed as other punctuation. I did the part where it checks that it name is from the alphabet , but how can I escape the single quote character and the space , so that they are also valid ?

I did this to validate if they are from alphabet , how can I modify this so that it can also accept single quotes and spaces ?

Code:

---

for (i = 0; i < length; i++)
        {
                if (!isalpha(name[i]))
                {       
                    printf("No punctuation is allowed except single quotes and spaces.\n\n");
                        return 0;
                }

---

You could probably just get rid of isalpha and use ASCII code verification to ensure that the characters in the input are in the 'a-z','A-Z' or ' ranges. I think isalpha does the same thing for letters anyway.

Check here for the full table: Ascii Table - ASCII character codes and html, octal, hex and decimal chart conversion

but how can it also accept single quote characters and spaces , but does not accept other punctuation marks ?

You have to write your own condition and get rid of isalpha:

i.e. if((mychar > 'a' and mychar < 'z')
OR
(mychar > 'A' and mychar < 'Z')
OR
mychar = '\'')

Or you can even use isalpha and add the extra condition. If isalpha(char) OR char = '\''

I am using this conditon :

name[i] !='\'' && name[i] !=' ' && !isalpha(name[i])

and it is working. The only problem I am seeing is that when for example the user enters : "Michael Paul" <-- testing the space condition , the second part "Paul" , is filling the surname[] field, instead of continuing on in the name field.

That's probably because you are reading strings with scanf and scanf stops at spaces.

what should I use then please?

Google fgets() and/or search this forum for examples. There are at least a dozen or so every single day. It is a common mistake for beginners to use scanf which stands for scan format, to read in nonformatted data, such as names.

EDIT: scanf is also bad for reading strings because you cannot control how much input you are willing to accept, potentially overflowing your storage.

oh ok thanks.

Quote:

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Originally Posted by claudiu

EDIT: scanf is also bad for reading strings because you cannot control how much input you are willing to accept, potentially overflowing your storage.

---

Code:

---

    scanf("%20s", buf);

---

willl read only 20 chars, you need a buffer of 21 chars including the \0
Kurt

Incidentally hyphenated names are quite common. It is fairly common in some circles that children get a combination of surnames. Have a look here for examples.