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April 1, 2020 23:59
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SPFIND
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| /****************************************************************************** | |
| * Author: Marcus Simpkins | |
| * Date: 4/1/2020 | |
| * Pledge: I pledge my honor that I have abided by the Stevens Honor System. | |
| * Project: HW4 - Permission Find & Sort | |
| ******************************************************************************/ | |
| #include <stdio.h> // pipe | |
| #include <stdlib.h> | |
| #include <string.h> // strlen, strerror, etc | |
| #include <stdbool.h> // bool values | |
| #include <libgen.h> // basename | |
| #include <getopt.h> // getpopt, etc | |
| #include <errno.h> // errors! :D | |
| #include <limits.h> // PATH_MAX | |
| #include <dirent.h> // readdir, struct dirent, etc. | |
| #include <sys/stat.h> // lstat, struct stat, etc. | |
| #include <sys/wait.h> // wait | |
| #include <unistd.h> | |
| /** | |
| * Displays the program's usage message when given a path to the program. | |
| **/ | |
| void display_usage(char *path) { | |
| char *prog_name = basename(path); | |
| printf("Usage: ./%s -d <directory> -p <permissions string> [-h]\n", prog_name); | |
| } | |
| /** | |
| * Returns true if the given string is valid, and returns false otherwise. | |
| **/ | |
| bool valid_permstring(const char *permstring) { | |
| bool valid = (strlen(permstring) == 9); | |
| for(int i = 0; i < 9 && valid; i += 3) { | |
| if (permstring[i] != 'r' && permstring[i] != '-') valid = false; | |
| if (permstring[i+1] != 'w' && permstring[i+1] != '-') valid = false; | |
| if (permstring[i+2] != 'x' && permstring[i+2] != '-') valid = false; | |
| } | |
| return valid; | |
| } | |
| /** | |
| * Main program logic | |
| **/ | |
| int main(int argc, char *argv[]) { | |
| // print usage if no args given | |
| if (argc == 1) { | |
| display_usage(argv[0]); | |
| return EXIT_SUCCESS; | |
| } | |
| // handle command line options | |
| char *dirpath = NULL; char *permstring = NULL; | |
| char opt; opterr = 0; | |
| while ((opt = getopt(argc, argv, "d:p:h")) != -1) { | |
| switch (opt) { | |
| case 'd': | |
| dirpath = optarg; | |
| break; | |
| case 'p': | |
| permstring = optarg; | |
| break; | |
| case 'h': | |
| display_usage(argv[0]); | |
| return EXIT_SUCCESS; | |
| /* case '?': */ | |
| /* fprintf(stderr, "Error: Unknown option '-%c' recieved.\n", optopt); */ | |
| /* return EXIT_FAILURE; */ | |
| case ':': | |
| fprintf(stderr, "Error: Option -%c expects argument.\n", optopt); | |
| return EXIT_FAILURE; | |
| } | |
| } | |
| // ensure option arguments were properly passed | |
| if (dirpath == NULL) { | |
| fprintf(stderr, "Error: Required argument -d <directory> not found.\n"); | |
| return EXIT_FAILURE; | |
| } | |
| if (permstring == NULL) { | |
| fprintf(stderr, "Error: Required argument -p <permissions string> not found.\n"); | |
| return EXIT_FAILURE; | |
| } | |
| // validate directory | |
| DIR *dir = opendir(dirpath); | |
| if (dir == NULL) { | |
| if (errno != EACCES) | |
| fprintf(stderr, "Error: Cannot stat '%s'. No such file or directory.\n", dirpath); | |
| else { | |
| char pathbuf[PATH_MAX + 1]; | |
| realpath(dirpath, pathbuf); | |
| fprintf(stderr, "Error: Cannot open directory '%s'. Permission denied.\n", pathbuf); | |
| } | |
| return EXIT_FAILURE; | |
| } else closedir(dir); | |
| // validate permstring | |
| if (!valid_permstring(permstring)) { | |
| fprintf(stderr, "Error: Permissions string '%s' is invalid.\n", permstring); | |
| return EXIT_FAILURE; | |
| } | |
| // forks and pipes | |
| int pfind_to_sort[2], sort_to_parent[2]; | |
| pipe(pfind_to_sort); pipe(sort_to_parent); | |
| pid_t pid[2]; // pid[0] = pfind, pid[1] = sort | |
| int status[2]; // exit status for pfind and sort. | |
| // fork: pfind | |
| if ((pid[0] = fork()) == 0) { | |
| // setup related pipes | |
| close(pfind_to_sort[0]); | |
| dup2(pfind_to_sort[1], STDOUT_FILENO); | |
| // close unrelated pipes | |
| close(sort_to_parent[0]); | |
| close(sort_to_parent[1]); | |
| // call pfind | |
| execlp("./pfind", "pfind", argv[1], argv[2], argv[3], argv[4], NULL); | |
| return EXIT_FAILURE; | |
| } | |
| // fork: sort | |
| if ((pid[1] = fork()) == 0) { | |
| // close old pipes | |
| close(pfind_to_sort[1]); | |
| // setup related pipes | |
| dup2(pfind_to_sort[0], STDIN_FILENO); | |
| dup2(sort_to_parent[1], STDOUT_FILENO); | |
| // close unrelated pipes | |
| close(sort_to_parent[0]); | |
| // call sort | |
| execlp("sort", "sort", NULL); | |
| } | |
| // close old pipes | |
| close(sort_to_parent[1]); | |
| // setup related pipes | |
| dup2(sort_to_parent[0], STDIN_FILENO); | |
| // close all unrelated pipes | |
| close(pfind_to_sort[0]); | |
| close(pfind_to_sort[1]); | |
| // print from the pipe character-by-character | |
| char c; int num_matches = 0; // start at -1 b/c there'll always be at least 1 newline | |
| while(read(STDIN_FILENO, &c, sizeof(char)) != 0) { | |
| putc(c, stdout); | |
| if (c == '\n') num_matches++; | |
| } | |
| // validate pfind's exit status | |
| wait(&status[0]); | |
| if (WEXITSTATUS(status[0]) != EXIT_SUCCESS) { | |
| fprintf(stderr, "Error: pfind failed.\n"); | |
| return EXIT_FAILURE; | |
| } | |
| // validate sort's exit status | |
| wait(&status[1]); | |
| if (WEXITSTATUS(status[1]) != EXIT_SUCCESS) { | |
| fprintf(stderr, "Error: sort failed.\n"); | |
| return EXIT_FAILURE; | |
| } | |
| printf("Total matches: %d\n", num_matches); | |
| return EXIT_SUCCESS; | |
| } |
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