l3e1 niv

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

void Error(char* msg){printf("%s\n",msg);exit(1);}

int main(int argc, char* argv[]){
    int file1, file2, answer, flag1, flag2, temp;
    char buffer[1];

    if(argc < 3)
        Error("Not enough files at argv[]");
    file1 = open(argv[1], O_RDONLY, 4);
    if(file1 == -1)
        Error("Can't open the file in arg[1]");
    file2 = open(argv[2], O_RDONLY, 4);
    if(file2 == -1)
        Error("Can't open the file in arg[2]");
    answer = open(argv[3], O_RDWR | O_CREAT,0644);
    if(answer == -1)
        Error("Can't open the file in arg[3]");

    do{
        do{
            temp = read(file1,buffer,1);
            if(temp == -1)
                Error("Can't read from file in arg[1]");
            if(!temp)
            {
                flag1=1;
                break;
            }
            temp = write(answer,buffer,1);
            if(temp==-1)
                Error("Can't write to file in arg[3]");
        }while(buffer[0]!='\n');
        do{
            temp = read(file2,buffer,1);
            if(temp==-1)
                Error("Can't read from file in arg[2]");
            if(!temp)
            {
                flag2=1;
                break;
            }
            temp = write(answer,buffer,1);
            if(temp==-1)
                Error("Can't write to file in arg[3]");
        }while(buffer[0]!='\n');
    }while(flag1!=1 && flag2!=1);
    return 1;
}