| 1 | #include <stdio.h> |
| 2 | #include <fcntl.h> |
| 3 | #include <unistd.h> |
| 4 | |
| 5 | #include <sys/stat.h> |
| 6 | |
| 7 | int main(int argc, char *argv[]) { |
| 8 | |
| 9 | int cur, flag_append, flag_force; |
| 10 | int fd_from, fd_to, mode; |
| 11 | char buf[1]; |
| 12 | |
| 13 | flag_append = 0; |
| 14 | flag_force = 0; |
| 15 | |
| 16 | while((cur = getopt(argc, argv, "af")) != -1) { |
| 17 | switch(cur) { |
| 18 | |
| 19 | case 'a': |
| 20 | flag_append = 1; |
| 21 | break; |
| 22 | |
| 23 | case 'f': |
| 24 | flag_force = 1; |
| 25 | break; |
| 26 | |
| 27 | default: |
| 28 | printf("invalid argument\n"); |
| 29 | return 1; |
| 30 | } |
| 31 | } |
| 32 | |
| 33 | if(argc - optind != 2) { |
| 34 | |
| 35 | printf("invalid number of args\n"); |
| 36 | return 1; |
| 37 | |
| 38 | } else if(flag_append && flag_force) { |
| 39 | |
| 40 | printf("cannot simultaneously specify overwrite and append\n"); |
| 41 | return 1; |
| 42 | } |
| 43 | |
| 44 | if(access(argv[optind + 1], F_OK) != -1 && !flag_append && !flag_force) { |
| 45 | |
| 46 | printf("destination file already exists, pass -f to overwrite\n"); |
| 47 | return 1; |
| 48 | } |
| 49 | |
| 50 | if(flag_force) mode = O_TRUNC; |
| 51 | else if(flag_append) mode = O_APPEND; |
| 52 | else mode = O_CREAT; |
| 53 | |
| 54 | fd_from = open(argv[optind], O_RDONLY); |
| 55 | fd_to = open(argv[optind + 1], mode | O_WRONLY, S_IRWXU); |
| 56 | |
| 57 | if(fd_from == -1) { |
| 58 | |
| 59 | printf("could not open source file\n"); |
| 60 | return 1; |
| 61 | |
| 62 | } else if(fd_to == -1 && !flag_force && !flag_append) { |
| 63 | |
| 64 | printf("could not create new destination file\n"); |
| 65 | return 1; |
| 66 | |
| 67 | } else if(fd_to == -1) { |
| 68 | |
| 69 | } |
| 70 | |
| 71 | while(read(fd_from, buf, 1) == 1) |
| 72 | write(fd_to, buf, 1); |
| 73 | |
| 74 | close(fd_from); |
| 75 | close(fd_to); |
| 76 | |
| 77 | return 0; |
| 78 | } |