How to parse through a string of STDIN word by word in C-CodePudding

I would like to read standard input of a command and its argument in a C program, for instance:

ATTACK 50 30

I would like my program to parse through the input using whitespace and assign each word to a variable but right now I would just like to print each word. However, when I tried the program only returned ATTACK and not ATTACK 50 30.

I tried:

int main(){

    // Grid size declaration //
    int *x, *y;
    char command[20];

    char user_input[100];
    scanf("%s", user_input);
    printf("%s", user_input);

    return 0;
}

As I said I used ATTACK 50 30 as my STDIN but my printf function only returned ATTACK. I thought of maybe using a while loop to keep scanning until the character interpreted is the return key (which I believe in this case would just be the null character?). I tried it using the code below:

int main(){

    // Grid size declaration //
    int *x, *y;
    char command[20];

    char user_input[100];
        while(scanf("%s", user_input)!="\0"){
    scanf("%s", user_input);
    printf("%s", user_input);
        }
    return 0;
}

This did not work, the error produced declared I was comparing a pointer to an integer.

CodePudding user response：

Since you are dealing with stdin it would probably be a better idea to utilize the fgets function in lieu of the scanf function, and then parse the inputted line of data utilizing the strtok string function.

Utilizing that strategy, following is a snippet of code allowing for the parsing of entered text where each word or data group is identified.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX 64

int main()
{

    char line[MAX   1];
    const char delim[2] = " ";
    char * wd;

    printf("Enter some text or type \"quit\" to end: ");

    while (fgets(line, MAX, stdin))
    {
        line[strlen(line) - 1] = ' ';   /* Replace newline character at the end with a space */
        wd = strtok(line, delim);

        while (wd != NULL)
        {
            if (strcmp(wd, "quit") == 0)
            {
                return 0;
            }
            printf("%s\n", wd);
            wd = strtok(NULL, delim);
        }
        printf("Enter some text or type \"quit\" to end: ");
    }

    return 0;
}

Testing out this code utilizing your text example yielded the following terminal output.

@Dev:~/C_Programs/Console/ParseWord/bin/Release$ ./ParseWord 
Enter some text or type "quit" to end: ATTACK 50 30
ATTACK
50
30
Enter some text or type "quit" to end: quit
@Dev:~/C_Programs/Console/ParseWord/bin/Release$

This is just a springboard from where you might go, but test that out and see if it meets the spirit of your project.