如何将函数内部的printf输出输出到c中的主程序

Question

I have a function which print lot of printf statements, number of lines as output is not fixed. I need to get all the lines which are getting printed in myFun to the main function and used them for some other purpose. Can someone please guide how to do that ?

#include<stdio.h>


int myFun(char* name){
    printf("myFun: this is important line too\n");
    printf("myFun: my name is %s\n",name);
    printf("myFun: this is a important line needed in main, genrated from some function called inside myFun\n");
}

int main(){


    printf("this is main and now calling myFun\n");
    myFun("monk");

    //how can I get all the output of all three printf statements done inside myFun to the main function ?


    return 0;
}

Answer 1

You could try saving the strings into an array, and return ing the whole array:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char **Func(char *name)
{
    int numOfOutputs = 3;
    numOfOutputs++; //Append an extra null byte to the end so we know when it ends
    int maximumStringSize = 100;
    char **final = (char **)malloc(numOfOutputs * sizeof(char *));
    for (int i = 0; i < numOfOutputs; i++)
        final[i] = (char *)malloc(maximumStringSize * sizeof(char));

    strcpy(final[0], "myFun: this is important line too\n");
    sprintf(final[1], "myFun: my name is %s\n", name);
    strcpy(final[2], "myFun: this is a important line needed in main, genrated from some function called inside myFun\n");

    //Final member assigned as NULL to indicate end
    final[3] = NULL;
    return final;
}
int main()
{
    printf("this is main and now calling myFun\n");
    char **result = Func("monk");
    //Print result, check for ending member with the nullbyte we added
    for(int i = 0 ; result[i] != NULL; i++)
        printf("For i = %d, string is -> %s", i, result[i]);
    //Don't forget to free with something like this:
    for(int i = 0 ; result[i] != NULL; i++)
        free(result[i]);
    free(result);
    return 0;
}