第3章 目录与文件属性：编写ls

/* * ls1.c * purpose list contents of directory or directories * action if no args, use . else list files in args */#include <stdio.h>#include <sys/types.h>#include <dirent.h>void do_ls(char []);main(int ac, char *av[]){    if (ac == 1)        do_ls(".");    else        while (--ac) {            printf("%s:\n", *++av);            do_ls(*av);        }}void do_ls(char dirname[])    /*     * list files in directory called dirname     */{    DIR *dir_ptr;       /* the direcotry */    struct dirent *direntp; /* each entry */    if ((dir_ptr = opendir(dirname)) == NULL )        fprintf(stderr, "ls1:cannot open %s\n", dirname);    else    {        while ((direntp = readdir(dir_ptr)) != NULL)            printf("%s\n", direntp->d_name);        closedir(dir_ptr);    }}

/* * ls2.c * purpose list contents of directory or directories * action if no args, use . else list files in args * note uses stat and pwd.h and grp.h * BUG: try ls2 /tmp */#include <stdio.h>#include <sys/types.h>#include <dirent.h>#include <sys/stat.h>void do_ls(char []);void dostat(char *);void show_file_info(char *, struct stat *);void mode_to_letters(int, char []);char *uid_to_name(uid_t);char *gid_to_name(gid_t);void main(int ac, char *av[]){    if (ac == 1)        do_ls(".");    else        while (--ac) {            printf("%s:\n", *++av);            do_ls(*av);        }}void do_ls(char dirname[])    /*     * list files in directory called dirname     */{    DIR *dir_ptr;       /* the directory */    struct dirent *direntp; /* each entry */    if ((dir_ptr = opendir(dirname)) == NULL)        fprintf(stderr, "ls1:cannot open %s\n", dirname);    else    {        while ((direntp = readdir(dir_ptr)) != NULL)            dostat(direntp->d_name);        closedir(dir_ptr);    }}void dostat(char *filename){    struct stat info;    if(stat(filename, &info) == -1)     /* cannot stat */        perror(filename);       /* say why */    else                    /* else show info */        show_file_info(filename, &info);}void show_file_info(char *filename, struct stat *info_p)    /*     * display the info about filename. The info is stored in struct at *info_p     */{    char    *uid_to_name(), *ctime(), *gid_to_name(), *filemode();    void    mode_to_letters();    char    modestr[11];    mode_to_letters(info_p->st_mode, modestr);    printf("%s", modestr);    printf("%4d ", (int)info_p->st_nlink);    printf("%-8s ", uid_to_name(info_p->st_uid));    printf("%-8s ", gid_to_name(info_p->st_gid));    printf("%8ld ", (long)info_p->st_size);    printf("%.12s ", 4 + ctime(&info_p->st_mtime));    printf("%s\n", filename);}/* * utility functions *//* * This function takes a mode value and a char array * and puts into the char array the file type and the * nine letters that correspond to the bits in mode. * NOTE: It does not code setuid, setgid, and sticky * codes */void mode_to_letters(int mode, char str[]){    strcpy(str, "----------");      /* default = no perms */    if (S_ISDIR(mode)) str[0] = 'd';    /* directory? */    if (S_ISCHR(mode)) str[0] = 'c';    /* char devices */    if (S_ISBLK(mode)) str[0] = 'b';    /* block devices */    if (mode & S_IRUSR) str[1] = 'r';   /* 3 bits for user */    if (mode & S_IWUSR) str[2] = 'w';    if (mode & S_IXUSR) str[3] = 'x';    if (mode & S_IRGRP) str[4] = 'r';   /* 3 bits for group */    if (mode & S_IWGRP) str[5] = 'w';       if (mode & S_IXGRP) str[6] = 'x';    if (mode & S_IROTH) str[7] = 'r';   /* 3 bits for other */    if (mode & S_IWOTH) str[8] = 'w';    if (mode & S_IXOTH) str[9] = 'x';}#include <pwd.h>char *uid_to_name(uid_t uid)    /*     * returns pointer to username associated with uid, uses getpw()     */{    struct passwd *getpwuid(), *pw_ptr;    static char numstr[10];    if ((pw_ptr = getpwuid(uid)) == NULL) {        sprintf(numstr, "%d", uid);        return numstr;    }    else        return pw_ptr->pw_name;}#include <grp.h>char *gid_to_name(gid_t gid)    /*     * returns pointer to group number gid. used getgrgid(3)     */{    struct group *getgrgid(), *grp_ptr;    static char numstr[10];    if ((grp_ptr = getgrgid(gid)) == NULL) {        sprintf(numstr, "%d", gid);        return numstr;    }    else        return grp_ptr->gr_name;}