program

#define BUFSIZE 1000

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

int init_files(FILE **src, FILE **tmp, char *file_path);
void print_file(FILE *src);
int write(FILE *src, FILE **dest, char* file_path, int *lines);
int memberOf(int val, int *array);

int parse_input(int argc, char *argv[]);

int main(int argc, char *argv[])
{
    /* init */

    FILE *fptr_src;
    FILE *fptr_tmp;

    char *file_path = "./test.txt";
    char *buf = malloc(sizeof(char)*BUFSIZE);

    int *lines = malloc(sizeof(int)*100);
    int i;
    for (i = 0; i < 100; ++i) {
        lines[i] = -1;
    }

    if (init_files(&fptr_src, &fptr_tmp, file_path)) {
        exit(1);
    }


    if (argc > 1) {
        switch(parse_input(argc, argv)) {
        case 0:
            if (argv[2])
                fprintf(fptr_tmp, "%s\n", argv[2]);
            else
                printf("error: must supply arguemnt for add\n");
            break;
        case 1:
            print_file(fptr_tmp);
            break;
        case 2: ;
            int j;
            i = 2, j = 0;
            while(argv[i]) {
                lines[j++] = atoi(argv[i++]);
            }
            break;
        default:
            printf("command not regocognized\n");
            break;
        }
    } else {
        printf("no arguments given\n");
    }

    write(fptr_tmp, &fptr_src, file_path, lines);

    fclose(fptr_src);
    fclose(fptr_tmp);

    return 0;
}

/* input parsing */

int parse_input(int argc, char *argv[])
{
    const char *commands[] = { "add", "ls", "rm" , NULL };
    int i = 0;

    while (commands[i]) {
        if (!strcmp(commands[i++], argv[1])) {
            return i-1;
        }
    }
    return -1;
}

/* file operations */

int init_files(FILE **src, FILE **tmp, char *file_path)
{
    char *buf = malloc(sizeof(char)*BUFSIZE);

    *src = fopen(file_path, "r");
    *tmp = fopen("./.test.tmp", "w+");
    if (*src == NULL || *tmp == NULL) {
        perror("Error:");
        return 1;
    }

    rewind(*src);

    /* else, copy data into tmp */
    int i = 0;
    while(fgets(buf, BUFSIZE, *src)) {
        fprintf(*tmp, "%s", buf);
    }
    return 0;
}

void print_file(FILE *src)
{
    char *buf = malloc(sizeof(char)*BUFSIZE);
    int i = 0;

    rewind(src);

    while(fgets(buf, BUFSIZE, src)) {
        printf("%d - %s", i++, buf);
    }
}

int write(FILE *src, FILE **dest, char *file_path, int *lines) {
    char *buf = malloc(sizeof(char)*BUFSIZE);

    fclose(*dest);

    *dest = fopen(file_path, "w+");

    if (*dest == NULL) {
        perror("Error: ");
        return 1;
    }

    rewind(src);
    int i = 0;

    while (fgets(buf, BUFSIZE, src)) {
        if (!memberOf(i++, lines)) {
            fprintf(*dest, "%s", buf);
        }
    }
    return 0;
}

int memberOf(int val, int *arr)
{
    int i;
    for (i = 0; i < 100; ++i) {
        if (arr[i] == val) {
            return 1;
        }
    }
    return 0;
}