linux下ls命令（支持-R參数）的c语言实现：

#include <stdio.h>

#include <sys/types.h>

#include <dirent.h>

#include <sys/stat.h>

#include <pwd.h>

#include <grp.h>

#include <string.h>

void do_ls(char *);

void do_stat(char *,char *);

void show_file_info(char *,struct stat *,char *);

void mode_to_letters(int ,char []);

char * uid_to_name(uid_t);

char * gid_to_name(gid_t);

int recursive = 0;

int main(int argc,char * argv[])

{

	int i;

	for(i = 1;i < argc;i++)

	{

		if(strcmp(argv[i],"-R") == 0)

		{

			recursive = 1;

			break;

		}

	}

	if(argc == 1 && recursive == 0)

		do_ls(".");

	else if(argc == 2 && recursive == 1)

		do_ls(".");

	else

	{

		int index = 1;

		while(argc > 1)

		{

			if(strcmp(argv[index],"-R") != 0)

				do_ls(argv[index]);

			index++;

			argc--;

		}

	}

	return 0;

}

void do_ls(char * path)

{

	DIR * dir;

	struct dirent * direntp;

	if((dir = opendir(path)) != NULL)

	{

		while((direntp = readdir(dir)) != NULL)

		{

			char absolute_pathname[255];

			strcpy(absolute_pathname,path);

			strcat(absolute_pathname,"/");

			strcat(absolute_pathname,direntp->d_name);

			printf("%s\n",absolute_pathname);

			do_stat(absolute_pathname,direntp->d_name);

		}

		closedir(dir);

	}

	else

		fprintf(stderr,"can't open %s",path);

}

void do_stat(char * absolute_filename,char * filename)

{

	struct stat  s;

	if(lstat(absolute_filename,&s) == -1)

		perror(absolute_filename);

	else

		show_file_info(absolute_filename,&s,filename);

}

void show_file_info(char * absolute_filename,struct stat * info,char * filename)

{

	char mode[11];

	mode_to_letters(info->st_mode,mode);

	printf("%s ",mode);

	printf("%d ",info->st_nlink);

	printf("%s ",uid_to_name(info->st_uid));

	printf("%s ",gid_to_name(info->st_gid));

	printf("%d ",info->st_size);

	printf("%.12s ",4+ctime(&info->st_mtime));

	printf("\n");

	if(recursive == 1)

	{

		if(S_ISDIR(info->st_mode) && strcmp(filename,".") != 0 && strcmp(filename,"..") != 0)

			do_ls(absolute_filename);

	}

}

void mode_to_letters(int mode,char * c_mode)

{

	strcpy(c_mode,"----------");

	if(S_ISDIR(mode))

		c_mode[0] = 'd';

	if(S_ISCHR(mode))

		c_mode[0] = 'c';

	if(S_ISBLK(mode))

		c_mode[0] = 'b';

	if(mode & S_IRUSR)

		c_mode[1] = 'r';

	if(mode & S_IWUSR)

		c_mode[2] = 'w';

	if(mode & S_IXUSR)

		c_mode[3] = 'x';

	if(mode & S_IRGRP)

                c_mode[4] = 'r';

        if(mode & S_IWGRP)

                c_mode[5] = 'w';

        if(mode & S_IXGRP)

                c_mode[6] = 'x';

	if(mode & S_IROTH)

                c_mode[7] = 'r';

        if(mode & S_IWOTH)

                c_mode[8] = 'w';

        if(mode & S_IXOTH)

                c_mode[9] = 'x';

	if(mode & S_ISUID)

		c_mode[3] = 's';

	if(mode & S_ISGID)

		c_mode[6] = 's';

	if(mode & S_ISVTX)

		c_mode[9] = 's';

}

char * uid_to_name(uid_t uid)

{

	struct passwd * passwd_pointer;

	passwd_pointer = getpwuid(uid);

	return passwd_pointer->pw_name;

}

char * gid_to_name(gid_t gid)

{

	struct group * group_pointer;

	static char numstr[10];

	if((group_pointer = getgrgid(gid)) == NULL)

	{

		sprintf(numstr,"%d",gid);

		return numstr;

	}

	return group_pointer->gr_name;

}