CODEWITHSUNDEEP
cclion
dbconfession
dbconfession

Reputation: 1199

C getchar() works properly in terminal but not CLion

The code below should first prompt "Type a Letter: ". Once enter is pressed, the output should show "You typed: <achar>."

I'm using Jet Brains IDE, CLion. Yesterday the code worked as described above. Today, however, when I run the code, I get a blank line. If a key is pressed followed by enter, I get the output:

Letter: You typed: <achar>

If, however, I put a \n after "Type a letter: ", the prompt shows but outputs the pressed key on the next line because of the \n.

I've copied the exact code into a .c file, compiled and run it in Terminal and it runs as expected. 

#include <stdio.h>

int main() {
    int c;
    printf("Type a letter: "); // works if \n used, but jumps to next line when key pressed
    c = getchar();
    printf("You typed: %c\n", c);
    return (0);
}

Upvotes: 0

Views: 931

Answers (2)

Michi
Michi

Reputation: 5307

It happens because after you type a letter and you hit ENTER you actually have your Letter (eg: A) and the new line (\n)character. This means that you need to clean the Buffer.

Try the following:

    #include <stdio.h>

int main(void) {
    int c;
    printf("Type a letter: "); // works if \n used, but jumps to next line when key pressed
    while((c = getchar()) != 0 && c != '\n' && c != EOF);

    printf("You typed: %c\n", c);
    return 0;
}

Upvotes: 0

user3121023
user3121023

Reputation: 8296

The terminal is buffered. printf("Type a letter: "); if the printf contains a newline('\n') it is printed. Without a newline, you can force the printf by calling fflush(stdout); otherwise the printf waits until the buffer is full before printing.
Be aware that input streams should NOT be flushed as fflush(stdin);

Upvotes: 3

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