在 fork 中调用一个函数，该函数内是一个 while 循环，它应该读取输入，但是，完全跳过了 scanf()

Question

Here is where main() forks and calls the function:

#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <signal.h>
#include <errno.h>


#include"sp-pipe-client.h"

pid_t clientChild, serverChild, c1 child1Stat;

int main() {

    if ((serverChild = fork()) == 0) {

    }
    else if ((clientChild = fork()) == 0) {
        SP_Pipe_Client();
    }
    else {
        c1 = wait(&child1Stat);
    } 
}

header:

void SP_Pipe_Client();

And here is the function in which scanf is being completely skipped, while loop goes infinite printing the menu:

#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <signal.h>
#include <errno.h>

char input = 'a', fileName[50];
int puzzleSize = 4;
int tile;

void SP_Pipe_Client() {
    while (input != 'q') {
        //  if (IsGameWon(puzzleSize, slidingPuzzle)) {
        //      printf("Congratulations, you have won the game!\n");
        //  }

        printf("Menu: [p]rint, [m]ove, [n]ew, [s]ave, [l]oad, [q]uit?\n");
        scanf(" %c", &input);
        if (input == 'p') {
            //DisplayBoard(puzzleSize, slidingPuzzle);
        }
        else if (input == 'm') {
            printf("Enter tile # to move: ");
            scanf(" %d", &tile);
            //MovePiece(tile, puzzleSize, slidingPuzzle, rowP, colP);
        }
        else if (input == 'n') {
            printf("Enter a size for new game (2-10): ");
            scanf(" %d", &puzzleSize);
            while (puzzleSize < 2 || puzzleSize > 10) {
                printf("Enter a valid size for new game (2-10): ");
                scanf(" %d", &puzzleSize);
            }
            //free(slidingPuzzle);
            //slidingPuzzle = Initialize(puzzleSize);

        }
        else if(input == 's'){
            printf("Please enter file name for saving. (max 30 characters including '.txt'\n");
            scanf("%s", fileName);
            //SaveGame(puzzleSize, slidingPuzzle, fileName);
        }
        else if(input == 'l'){
            printf("Please enter file name for saving. (max 30 characters including '.txt'\n");
            scanf("%s", fileName);
            //slidingPuzzle = LoadGame(size, fileName, slidingPuzzle);
        }
        else if(input == 'q') {
            //TearDown(slidingPuzzle);
            exit(0);
        }
        else {
            printf("Invalid input, try again\n");
        }
    }
}

The main function is supposed to call this function and a server function that I have yet to code, these functions are within their own .c files. When forked the child calls the function and infinitely prints the menu and the else statement at the bottom.

I have already tried changing which side of "%c" eats the \\n , as well as giving it to both sides and using \\n itself, I have also tried fgetc() both to eat the new line and to get input itself but no matter what the loop remains infinite, scanf() and fgetc() never occur.

Edit: Also I have tried moving my variable declarations, they used to be inside the function called by the child, made no difference as well.

Answer 1

I have figured it out. The problem is that I only called wait() one time, but I made two child processes, so my main was waiting for only one child to die, which because I haven't written code for my server child it was ending and so my main process was ending, leaving the client child to continue on it's own as an orphan and not take any input. I fixed this by adding "c2 = wait(&child2Stat);"to the else statement allowing my main process to wait for both the client and server children:

int main(){

pipe(pipe_command);
pipe(pipe_param_result);

if((serverChild = fork()) == 0){

}
else if((clientChild = fork()) == 0){
SP_Pipe_Client();

}
else{
    c1 = wait(&child1Stat);
    c2 = wait(&child2Stat);
}
 
}