Reading from stdin

This is a discussion on Reading from stdin within the C Programming forums, part of the General Programming Boards category; Hi, I am writing a program that reads in from stdin and writes into a string. Code: int main() { ...

  1. #1
    Registered User
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    Aug 2009
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    Reading from stdin

    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

  2. #2
    Registered User hk_mp5kpdw's Avatar
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    #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.
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  3. #3
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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