lazysphere/command/chown.c

/**
 *  file: chown.c
 *  command: chown
 *  author: Tyler Murphy
 */

#include "command.h"
#include "lslib.h"

#include <dirent.h>
#include <grp.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <pwd.h>

/**
 * File flags to be used with chown
 */
static struct {
    bool recurse;       /* -R if to recurse directorys */
    bool list_changed;  /* -c if to list what was changed */
    bool verbose;       /* -v if to list all output */
    bool quiet;         /* -f if to silence errors */
    uid_t uid;          /* the uid to set the file to */
    gid_t gid;          /* the gid to set the file to */
} flags;

/**
 * Help function for chown
 */
static void help (void) {
    printf("Usage: chown [-Rcvf]... USER[:[GRP]] FILE...\n\n");
    printf("Change the owner and/or group of FILEs to USER and/or GRP\n\n");
    printf("\t-R\tRecurse\n");
	printf("\t-c\tList changed files\n");
	printf("\t-v\tVerbose\n");
	printf("\t-f\tHide errors\n");
}

/** 
 * Takes in each argument that has a single - and parses it 
 * @param c the character after the -
 * @param next the next argument in argv that hasnt been parsed
 * @reutrn if the next arg was used or if the arg was invalid
 */
static int short_arg(char c, char* next) {
    UNUSED(next);
    switch (c) {
        case 'R':
            flags.recurse = true;
            break;
        case 'c':
            flags.list_changed = true;
            break;
        case 'v':
            flags.verbose = true;
            break;
        case 'f':
            flags.quiet = true;
            break;
        default:
            return ARG_INVALID;
    }
    return ARG_UNUSED;
}

/**
 * Given a file path change the filw ownership with the given flags
 * @param path the file to change the ownership
 */
static void chown_file(char* path) {

    /* allocate arguments on the stack */
    int save; /* path buffer save */
    struct stat s; /* file stats */
    DIR* d; /* recursing dir if recursing */
    struct dirent* file; /*if recursing current file being read */

    save = push_path_buffer(path);
    
    /* attempt to change file ownership, if failed error and return */
    if (chown(get_path_buffer(), flags.uid, flags.gid) < 0) {
        if (!flags.quiet) {
            error_s("cannot chown '%s'", get_path_buffer()); /* error if failed */
        }
        pop_path_buffer(save); /* cleanup */
        return;
    } else if (flags.list_changed) { /* list changed if verbose */
        output("changed '%s' to %u:%u", get_path_buffer(), flags.uid, flags.gid);
    }

    /* if not recurse dont do future checks and return */
    if (!flags.recurse) {
        pop_path_buffer(save);
        return;
    }

    /* stat file info and return if failed */
    if (lstat(get_path_buffer(), &s) < 0) {
        if (!flags.quiet) {
            error_s("cannot stat '%s'", get_path_buffer()); /* error if failed */
        }
        pop_path_buffer(save); /* clean up */
        return;
    }

    /* if not dir, cannot recurse so return */
    if (!S_ISDIR(s.st_mode)) {
        pop_path_buffer(save); /* clean up */
        return;
    }

    /* open dir, if failed return and error */
    d = opendir(get_path_buffer());
    if (d == NULL) {
        if (!flags.quiet) {
            error_s("cannot open dir '%s'", get_path_buffer()); /* error if failed */
        }
        pop_path_buffer(save); /* clean up */
        return;
    }

    /* read each file in directory, and modify its ownership recursivly */
    while ((file = readdir(d)) != NULL) {
        if (is_dot_dir(file->d_name)) continue; /* if dot dir skip */
        chown_file(file->d_name);
    }
    
    /* clean up */
    closedir(d);
    pop_path_buffer(save);
}

/** 
 * Parse a given user and group from a string
 * @param str the stirng to parse
 */
static void parse_ownership(char* str) {
    char* user = str; /* a copy of the input string */
    char* group = NULL; /* the group name found in str */
    char* end = NULL; /* the end of a string to parse a number if passed */
    unsigned long i; /* a number i */
    struct passwd* p = NULL; /* a user if found */
    struct group* g = NULL; /* a group if found */
    
    /* attempy to find a colon seperating the user and group in the string, if not parse it as a user only */
    for (i = 0; i < strlen(str); i++) {
        if (str[i] == ':') {
            str[i] = '\0';
            group = &str[i] + 1;
            break;
        }
    }

    /* attempt to parse input as a number */
    flags.uid = strtol(user, &end, 10);
    if (end != user) goto group; /* if successfull they ave a direct uid */

    /* if not try to get the user by the string */
    if ((p = getpwnam(user)) == NULL) {
        error("invalid user '%s'", user); /* error and abort if failed */
    } else {
        flags.uid = p->pw_uid; /* update flags */
    }

group:

    /* if the group string was not found set the gorup to the user */
    if (group == NULL) {
        if (p == NULL) {
            flags.gid = flags.uid; /* if a int was passed set that int to the group as well */
        } else {
            flags.gid = p->pw_gid; /* if a user was passed set the group to the users gid */
        }
        return;
    }

    /* if a group was passed, attempt to parse it as a gid first */
    flags.gid = strtol(group, &end, 10);
    if (end != group) return; /* if succssfull return were done */

    /* otherwise try to get the group from the name */
    if ((g = getgrnam(group)) == NULL) {
        error("invalid group '%s'", group); /* error and abort if failed */
    } else {
        flags.gid = g->gr_gid; /* update gid */
    }
}

COMMAND(chown_main) {

    int start, i;
    
    /* set default flags for chown */
    flags.recurse = false;
    flags.list_changed = false;
    flags.verbose = false;
    flags.quiet = false;

    /* parse argument */
    start = parse_args(argc, argv, help, short_arg, NULL);

    /* if no more arguments error and abort since no ownership passed */
    if (argc - start < 1) {
        if (!flags.quiet) { /* if not set to hide errors */
            error("no onwership passed");
        } else {
            return EXIT_FAILURE;
        }
    }

    parse_ownership(argv[start]);

    /* if not more arugumnets error and abort since no files passed */
    if (argc - start < 1) {
        if (!flags.quiet) { /* if not set to hide errors */
            error("no files passed"); 
        } else {
            return EXIT_FAILURE;
        }
    }

    /* change ownership for each file passed */
    for (i = start + 1; i < argc; i++) {
        chown_file(argv[i]);
    }

    return EXIT_SUCCESS; /* done */
}