20145338 索朗卓嘎《信息安全系统设计基础》第10学习总结

20145338 索朗卓嘎《信息安全系统设计基础》第10学习总结

代码

1.cp

include <stdio.h>

include <stdlib.h>

include <unistd.h>

include <fcntl.h>//宏和open

define BUFFERSIZE 4096//存储器容量

define COPYMODE 0644//复制长度

void oops(char *, char *);

int main(int argc, char *argv[])
{
int in_fd, out_fd, n_chars;//三个描述符值
char buf[BUFFERSIZE];

if (argc != 3) {
fprintf(stderr, "usage: %s source destination ", argv);
exit(1);
}
/检查cp的第一个参数，要复制的文件，用open打开，in_fd为open返回的描述符*/
if ((in_fd = open(argv[1], O_RDONLY)) == -1)
oops("Cannot open ", argv[1]);

/检查cp的第二个参数，复制的目的地址，用create在目的地址创建新文件，out_fd为open返回的描述符/
if ((out_fd = creat(argv[2], COPYMODE)) == -1)
oops("Cannot creat", argv[2]);

/cp指令的动作就是读取一个文件的内容到存储器，在新的地址创建空白文件，再从存储器将内容写入新文件。/
while ((n_chars = read(in_fd, buf, BUFFERSIZE)) > 0)
if (write(out_fd, buf, n_chars) != n_chars)
oops("Write error to ", argv[2]);
if (n_chars == -1)
oops("Read error from ", argv[1]);

if (close(in_fd) == -1 || close(out_fd) == -1)
oops("Error closing files", "");
}

/这个是用来输出错误信息的函数/
void oops(char *s1, char *s2)
{
fprintf(stderr, "Error: %s ", s1);
perror(s2);
(stderr)
exit(1);
}
实现过程：1.开启源文件 2.创建目标文件 3.将源文件读入缓冲区 4.将缓冲区内容写入目标文件 5.关闭

2.ls1ls2

1.ls -l 以长格式的形式查看当前目录下所有可见文件的详细属性

2.ls -a 列出的内容包含以“.”开头的文件

3.ls -lu 最后访问时间

4.ls -s 以块为单位的文件大小

5.ls -t 按时间排序

6.ls -F 显示文件类型

include <stdio.h>

include <sys/types.h>

include <dirent.h>

void do_ls(char []);

int main(int argc, char *argv[])
{
if ( argc == 1 )
do_ls( "." );
else
while ( --argc ){
printf("%s: ", *++argv );
do_ls( *argv );
}

return 0;
}

void do_ls( char dirname[] )
{
DIR *dir_ptr;
struct dirent *direntp;

if ( ( dir_ptr = opendir( dirname ) ) == NULL )
fprintf(stderr,"ls1: cannot open %s ", dirname);
else
{
while ( ( direntp = readdir( dir_ptr ) ) != NULL )
printf("%s ", direntp->d_name );
closedir(dir_ptr);
}
}
此函数用来显示文件的详细信息：用户名，群组名，大小，创建时间，读写执行权

include <stdio.h>

include <string.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 );

int main(int argc, char *argv[])
{
if ( argc == 1 )
do_ls( "." );
else
while ( --argc ){
printf("%s: ", *++argv );
do_ls( *argv );
}

return 0;
}

void do_ls( char dirname[] )
{
DIR *dir_ptr;
struct dirent *direntp;

if ( ( dir_ptr = opendir( dirname ) ) == NULL )
fprintf(stderr,"ls1: cannot open %s ", 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 )
perror( filename );
else
show_file_info( filename, &info );
}

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

}

void mode_to_letters( int mode, char str[] )
{
strcpy( str, "----------" );

if ( S_ISDIR(mode) ) str[0] = 'd';
if ( S_ISCHR(mode) ) str[0] = 'c';
if ( S_ISBLK(mode) ) str[0] = 'b';

if ( mode & S_IRUSR ) str[1] = 'r';
if ( mode & S_IWUSR ) str[2] = 'w';
if ( mode & S_IXUSR ) str[3] = 'x';

if ( mode & S_IRGRP ) str[4] = 'r';
if ( mode & S_IWGRP ) str[5] = 'w';
if ( mode & S_IXGRP ) str[6] = 'x';

if ( mode & S_IROTH ) str[7] = 'r';
if ( mode & S_IWOTH ) str[8] = 'w';
if ( mode & S_IXOTH ) str[9] = 'x';
}

include <pwd.h>

char *uid_to_name( uid_t uid )
{
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 )
{
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;
}