Gcc compiler can not scan a character and come out from loop and terminate program

Question

//code for mvt. in this ch did not scan by compiler. ch is used as a condition for loop . Its initial value is 'y' , and if it goes to 'n' , loop breaks. In this code i am asking user if he/she want to continue then press y else n . but don't know why gcc do not wait for scan it. It is a simple code but i can not get the mistake.

    int main(){
    char ch;
    temp=tm;
    ch='y';
    for(i=0;ch=='y';i++){
    printf("enter memory size for process %d",i+1);
    scanf("%d",&m);
    if(m<temp)
    {printf("memory allocated\n"); ms[n]=m; n++;
    temp-=ms[i];
     }
    else 
    {printf("memory not allocated\n"); }
https://stackoverflow.com/users/10404087/rishabh-sharma
    printf("do you want to continue");
    scanf("%c",&ch);
    }
    printf("total memory : %d\n",tm);
    printf("process \t occupied \n");
    for(i=0;i<n;i++)
        printf("%7d \t %8d \n",i+1,ms[i]);
    printf("total externel fregment : %d \n",temp);
    return 0;
    }

You got paste the code as text in the question and not as image. — kiran Biradar, Sep 23 '18 at 14:43
Use a debugger. What is being read into `ch` by `scanf`? And then you can look up [scanf is reading new line character](https://stackoverflow.com/questions/44743789/scanf-is-reading-new-line-character) — Raymond Chen, Sep 23 '18 at 14:44
Please do not post pictures of code, just post the code as text. — alk, Sep 23 '18 at 14:44

Zahid Khan · Answer 1 · 2018-09-23T15:05:56.417

2

You have to use flushall() function that clears all buffers associated with input streams, and writes any buffers associated with output streams.

Added:flushall() isn't C, but a vendor specific extension.

OR

Other alternative is to use space before %c

Example

char ch;
scanf(" %c", &ch);

edited Sep 23 '18 at 15:05

answered Sep 23 '18 at 14:45

Zahid Khan

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I'd read all `char`s of the stream until `EOF` is detected. – alk Sep 23 '18 at 14:54
@alk but I think thats extra overhead. As in this case we know that it is just carriage return which has encountered so why we have to go through the buffer till `EOF` as this will raise time complexity. – Zahid Khan Sep 23 '18 at 14:58
@alk: do you mean EOF or EOL (end of line)? I'd suggest EOL is more helpful than EOF, though EOF is not necessarily wrong. – Jonathan Leffler Sep 23 '18 at 15:41

Gcc compiler can not scan a character and come out from loop and terminate program

1 Answers1