Reading from stdin

**windingprince** · 08-26-2009

Hi,

I am writing a program that reads in from stdin and writes into a string.

Code:

int main()
{
        int file;
        char *sb, c;

        while((c = getchar()) != '\n'){
                printf("Entered in\n");

                if (isalnum(c))
                        *sb++ = c;

                printf(" The String: %s\n" , sb);
        }
}

I enter few characters and hit enter expectign that the final printf statement would output a string coming all the characters. But I always get junk printed out. I tried to malloc(10) for *sb and tried to print again. I got blank string. Could someone please point out what is going wrong ? Is it a problem with using getchar() ?

Please suggest me a way to get series of characters to be copied as a single string to *sb
-Jeck

**hk_mp5kpdw** · 08-26-2009

#1. You need to either malloc memory for sb or point it to some preexisting buffer.
#2. If you continuously alter/move your sb pointer (*sb++)as you are writing to it, how do you expect to output the data correctly. Every time you try to print the string, your sb pointer is at the end of the data you've copied. You probably want another separate pointer that points to the start of your allocated memory or buffer that you can increment independently of the sb pointer.
#3. getchar returns an int.

**Elysia** · 08-27-2009

Using pointers without allocating them.

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