How do I make my C program count more than just one character?

Question

I'm trying to write a program that takes a file and a string by using Standard C functions, the program counts all the characters in the file which the string contains.

For example if the user writes:

counter.exe x.txt abcd

The program calculates the number of each character that the string contains: a, b ,c ,d in file x.txt

Sample message:

Number of 'a' characters in 'x.txt' file is: 12
Number of 'b' characters in 'x.txt' file is: 0
Number of 'c' characters in 'x.txt' file is: 3
Number of 'd' characters in 'x.txt' file is: 5

So far I've been able to make it print and count one character from the file, how do I make it count all the characters that I tell it to count, not just the first one from the string?

counter.c code:

#include<stdio.h>

int main() {

    int count = 0;
    char sf[20]; char rr; FILE* fp; char c;

    printf("Enter the file name :\n");
    gets(sf);

    printf("Enter the character to be counted :\n");
    scanf("%c", &rr);
    fp = fopen(sf, "r");

    while ((c = fgetc(fp)) != EOF)
    {
        if (c == rr)
            count++;
    }
    printf("File '%s' has %d instances of letter '%c'.", sf, count, rr);

    fclose(fp);
    return 0;
}

Answer 1

#define  SIZE 1024
char * malloc_buff(int dim){
    char *buf;
    buf=malloc(sizeof(char)*dim);
    if(buf==NULL){
        perror("Error in malloc");
    }
    return buf;
}


char * read_file(char * file){
    FILE* fd;
    char* file_pt;
    file_pt=malloc_buff(SIZE);
    errno=0;
    fd=fopen(file,"r+");
    if(errno!=0){
        fprintf(stderr,"error open file\n");
        exit(-1);
    }
    fread(file_pt,sizeof(char),SIZE,fd);
    if(fclose(fd)){
        fprintf(stderr,"errore close file\n");
        exit(-1);
    }
    return file_pt;
}
int main(int argc, char *argv[])
{
    char* content;
    content=malloc_buff(SIZE);
    content=read_file(argv[1]);
    int lenght_word=strlen(argv[2]);
    int counter[lenght_word];
    int i=0,x=0;
    for(x=0;x<lenght_word;x++){
        counter[x]=0;
    }
    while (content[i]!='\0'){
        for(x=0;x<lenght_word;x++){
            if (content[i]==argv[2][x]){
                counter[x]++;
            }
        }
        i++;
    }
    for(x=0;x<lenght_word;x++){
        printf("The values are: for %c is %d",argv[2][x],counter[x]);
    }
    return 0;
}