Wait for user input in C?

c, linux

Solution

From the GNU C Library Manual:

Function: char * fgets (char *s, int count, FILE *stream)

The fgets function reads characters from the stream stream up to and including a newline character and stores them in the string s, adding a null character to mark the end of the string. You must supply count characters worth of space in s, but the number of characters read is at most count − 1. The extra character space is used to hold the null character at the end of the string.

So, `fgets(key,1,stdin);` reads 0 characters and returns. (read: immediately)

Use `getchar` or `getline` instead.

Edit: fgets also doesn't return once `count` characters are available on the stream, it keeps waiting for a newline and then reads `count` characters, so "any key" might not be the correct wording in this case then.

You can use this example to avoid line-buffering:

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

int mygetch ( void ) 
{
  int ch;
  struct termios oldt, newt;
  
  tcgetattr ( STDIN_FILENO, &oldt );
  newt = oldt;
  newt.c_lflag &= ~( ICANON | ECHO );
  tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
  ch = getchar();
  tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );
  
  return ch;
}

int main()
{
    printf("Press any key to continue.\n");
    mygetch();
    printf("Bye.\n");
}

Problem

I'm trying to make a simple command that pauses for user input. I think it'll be useful in Bash scripts. Here's my code: ``` #include <stdio.h> int main() { char key[1]; puts("Press any key to continue..."); fgets(key,1,stdin); } ``` It doesn't even pause for user input. I tried earlier to use getch() (ncurses). What happened is, the screen went blank and when I pressed a key, it went back to what was originally on the screen, and I saw: ``` $ ./pause Press any key to continue... $ ``` It's somewhat what I wanted. But all I want is the equivalent of the `pause` command in DOS/Windows (I use Linux).

Original source

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