lovelove工作
This commit is contained in:
lzy
@@ -411,6 +411,11 @@ p1->read -> p2->write
|
||||
|
||||
### 程序中的重定向：`dup`, `dup2`
|
||||
```c
|
||||
/**
|
||||
* dup 和 dup2 都是复制文件描述符
|
||||
* dup2 可以指定新的文件描述符
|
||||
* dup 会返回一个新的文件描述符
|
||||
*/
|
||||
int dup(int oldfd);
|
||||
int dup2(int oldfd, int newfd);
|
||||
```
|
||||
@@ -687,7 +692,214 @@ long telldir(DIR *dirp);
|
||||
|
||||
## 系统数据文件和信息
|
||||
|
||||
> 不同环境可能有区别，以具体查询为准，这里以Linux为例
|
||||
|
||||
1. `/etc/passwd`
|
||||
```c
|
||||
/**
|
||||
* 通过用户名获取用户信息
|
||||
*/
|
||||
struct passwd *getpwuid(uid_t uid);
|
||||
|
||||
/**
|
||||
* 通过用户ID获取用户信息
|
||||
*/
|
||||
struct passwd *getpwnam(const char *name);
|
||||
|
||||
struct passwd {
|
||||
char *pw_name; /* username */
|
||||
char *pw_passwd; /* user password */
|
||||
uid_t pw_uid; /* user ID */
|
||||
gid_t pw_gid; /* group ID */
|
||||
char *pw_gecos; /* user information */
|
||||
char *pw_dir; /* home directory */
|
||||
char *pw_shell; /* shell program */
|
||||
};
|
||||
```
|
||||
|
||||
2. `/etc/group`
|
||||
```c
|
||||
/**
|
||||
* 通过组ID获取组信息
|
||||
*/
|
||||
struct group *getgrgid(gid_t gid);
|
||||
|
||||
/**
|
||||
* 通过组名获取组信息
|
||||
*/
|
||||
struct group *getgrnam(const char *name);
|
||||
|
||||
struct group {
|
||||
char *gr_name; /* group name */
|
||||
char *gr_passwd; /* group password */
|
||||
gid_t gr_gid; /* group ID */
|
||||
char **gr_mem; /* group members */
|
||||
};
|
||||
```
|
||||
|
||||
3. `/etc/shadow`
|
||||
ll显示root用户也不可读写，但是只有root用户才可读写
|
||||
这样是提醒你，即便是root用户，也不要随便读写这个文件
|
||||
|
||||
> 密码
|
||||
> hash - 混淆，不可逆
|
||||
> 如果原串一样，hash值也一样
|
||||
> 防备管理员监守自盗
|
||||
>
|
||||
> 加密 - 解密
|
||||
>
|
||||
> 加密为了安全，攻击成本大于收益
|
||||
> 安全？穷举：口令随机校验（第一遍明明对了给你报错，让你连续两遍成功输入正确）
|
||||
>
|
||||
> 推荐书籍：《应用密码学》
|
||||
|
||||
```c
|
||||
/**
|
||||
* 获得用户的密码信息
|
||||
*/
|
||||
struct *spwd getspnam(const char *name);
|
||||
|
||||
/**
|
||||
* 加密密码
|
||||
*
|
||||
* @prarm: key 密码
|
||||
* @prarm: salt 盐 杂字串
|
||||
*
|
||||
* 默认 md5 加密方式
|
||||
*/
|
||||
char *crypt(const char *key, const char *salt);
|
||||
|
||||
struct spwd {
|
||||
char *sp_namp; /* login name */
|
||||
char *sp_pwdp; /* encrypted password */
|
||||
long sp_lstchg; /* last change */
|
||||
long sp_min; /* min days between changes */
|
||||
long sp_max; /* max days between changes */
|
||||
long sp_warn; /* warning days before password
|
||||
expires */
|
||||
long sp_inact; /* days before account inactive */
|
||||
long sp_expire; /* days since 1970-01-01 until account
|
||||
expires */
|
||||
unsigned long sp_flag; /* reserved */
|
||||
};
|
||||
|
||||
/**
|
||||
* 输入提示符
|
||||
*/
|
||||
char *getpass(const char *prompt);
|
||||
```
|
||||
|
||||
4. 时间戳
|
||||
机器喜欢大整数 `time_t`
|
||||
人类喜欢字符串 `char *`
|
||||
程序员喜欢结构体 `struct tm`
|
||||
|
||||
```c
|
||||
|
||||
/**
|
||||
* 从内核获取以秒为单位的一个时戳
|
||||
* 从 UTC 1970年1月1日0时0分0秒 到现在的秒数
|
||||
*/
|
||||
time_t time(time_t *t);
|
||||
|
||||
// eg: 两种用法
|
||||
time_t stamp;
|
||||
time(&stamp);
|
||||
stamp=time(NULL);
|
||||
|
||||
/**
|
||||
* 将时间戳转换为结构体
|
||||
*/
|
||||
struct tm *gmtime(const time_t *timep);
|
||||
struct tm *localtime(const time_t *timep);
|
||||
|
||||
sturct tm {
|
||||
int tm_sec; /* seconds */
|
||||
int tm_min; /* minutes */
|
||||
int tm_hour; /* hours */
|
||||
int tm_mday; /* day of the month */
|
||||
int tm_mon; /* month */
|
||||
int tm_year; /* year */
|
||||
int tm_wday; /* day of the week */
|
||||
int tm_yday; /* day in the year */
|
||||
int tm_isdst; /* daylight saving time */
|
||||
/* daylight 夏令时调整 */
|
||||
};
|
||||
|
||||
/**
|
||||
* 将结构体转换为时间戳
|
||||
* ! 没有 const，可能更改 tm
|
||||
*/
|
||||
time_t mktime(struct tm *tm);
|
||||
|
||||
/**
|
||||
* 格式化输出时间
|
||||
*/
|
||||
size_t strftime(char *s, size_t max, const char *format,
|
||||
const struct tm *tm);
|
||||
|
||||
// eg
|
||||
strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", tm);
|
||||
```
|
||||
|
||||
|
||||
## 进程环境
|
||||
|
||||
### `main`函数
|
||||
```c
|
||||
int main(int argc, char *argv[]);
|
||||
```
|
||||
|
||||
### 进程的终止
|
||||
1. 正常终止:
|
||||
- 从`main`函数返回
|
||||
- 调用`exit`
|
||||
`void exit(int status);`
|
||||
status & 0377 有符号的char -128~127
|
||||
|
||||
- 调用`_exit`或者`_Exit`（系统调用）
|
||||
> `exit`与`_exit _Exit`的区别
|
||||
> `_exit`不执行`atexit`注册的函数，不刷新`stdio`缓冲区
|
||||
> 这样可以防止错误扩散
|
||||
- 最后一个线程从其启动例程返回
|
||||
- 最后一个线程调用了`pthread_exit`
|
||||
|
||||
2. 异常终止
|
||||
- 调用`abort`
|
||||
- 接到一个信号并终止
|
||||
- 最后一个线程对其取消请求作出响应
|
||||
|
||||
|
||||
```c
|
||||
/**
|
||||
* 注册一个函数，当进程终止时调用
|
||||
*
|
||||
* 钩子函数：逆序执行
|
||||
* 可以进行资源释放
|
||||
*/
|
||||
int atexit(void (*function)(void));// 钩子函数
|
||||
```
|
||||
|
||||
### 命令行参数的分析
|
||||
```c
|
||||
#include <unistd.h>
|
||||
|
||||
extern char *optarg; // 选项参数
|
||||
// optind: 下一个要处理的参数的索引
|
||||
extern int optind, opterr, optopt;
|
||||
|
||||
int getopt(int argc, char *const argv[], const char *optstring);
|
||||
|
||||
int getopt_long(int argc, char *const argv[], const char *optstring,
|
||||
const struct option *longopts, int *longindex);
|
||||
```
|
||||
|
||||
### 环境变量
|
||||
|
||||
### C程序的存储空间布局
|
||||
|
||||
### 库
|
||||
|
||||
### 函数之间正常的跳转
|
||||
|
||||
### 资源的获取及控制
|
||||
|
||||
34
C13-Linux系统编程/fs/100days.c
Normal file
34
C13-Linux系统编程/fs/100days.c
Normal file
@@ -0,0 +1,34 @@
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include <time.h>
|
||||
|
||||
#define TIMESTRSIZE 128
|
||||
|
||||
/**
|
||||
* @brief 找出100天以后是哪一天
|
||||
* @details
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
time_t stamp;
|
||||
struct tm *tm;
|
||||
char timestr[TIMESTRSIZE];
|
||||
|
||||
time(&stamp);
|
||||
tm = localtime(&stamp);
|
||||
strftime(timestr, TIMESTRSIZE, "Now: %Y-%m-%d", tm);
|
||||
puts(timestr);
|
||||
|
||||
tm->tm_mday += 100;
|
||||
// mktime 会先调整tm溢出的情况
|
||||
mktime(tm);
|
||||
strftime(timestr, TIMESTRSIZE, "100 days later: %Y-%m-%d", tm);
|
||||
puts(timestr);
|
||||
|
||||
exit(0);
|
||||
}
|
||||
37
C13-Linux系统编程/fs/atexit.c
Normal file
37
C13-Linux系统编程/fs/atexit.c
Normal file
@@ -0,0 +1,37 @@
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
|
||||
static void f1(void)
|
||||
{
|
||||
puts("f1() is working!");
|
||||
}
|
||||
|
||||
static void f2(void)
|
||||
{
|
||||
puts("f2() is working!");
|
||||
}
|
||||
|
||||
static void f3(void)
|
||||
{
|
||||
puts("f3() is working!");
|
||||
}
|
||||
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
puts("Begin!");
|
||||
|
||||
atexit(f1);
|
||||
atexit(f2);
|
||||
atexit(f3);
|
||||
|
||||
puts("End!");
|
||||
|
||||
exit(0);
|
||||
}
|
||||
// out:
|
||||
// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ ./atexit
|
||||
// Begin!
|
||||
// End!
|
||||
// f3() is working!
|
||||
// f2() is working!
|
||||
// f1() is working!
|
||||
46
C13-Linux系统编程/fs/check.c
Normal file
46
C13-Linux系统编程/fs/check.c
Normal file
@@ -0,0 +1,46 @@
|
||||
#include <crypt.h>
|
||||
#include <shadow.h>
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include <string.h>
|
||||
#include <unistd.h>
|
||||
|
||||
/**
|
||||
* @brief 加密输入的密码并与shadow文件中的密码进行比较
|
||||
* @details
|
||||
* !!! compile: gcc check.c -o check -lcrypt
|
||||
* !!! 需要root权限运行
|
||||
*
|
||||
* @param argc
|
||||
* @param argv [in] 用户名
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
if (argc < 2)
|
||||
{
|
||||
fprintf(stderr, "Usage:...\n");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
char *input_pass;
|
||||
struct spwd *shadowline;
|
||||
char *crypt_pass;
|
||||
|
||||
//* getpass()函数在输入密码时不会回显密码
|
||||
input_pass = getpass("PassWord: ");
|
||||
|
||||
//* getspnam()函数通过用户名获取shadow文件中的密码
|
||||
shadowline = getspnam(argv[1]);
|
||||
|
||||
//* 加密输入的密码
|
||||
crypt_pass = crypt(input_pass, shadowline->sp_pwdp);
|
||||
|
||||
if (0 == strcmp(crypt_pass, shadowline->sp_pwdp))
|
||||
puts("OK!");
|
||||
else
|
||||
puts("Error!");
|
||||
|
||||
exit(0);
|
||||
}
|
||||
13
C13-Linux系统编程/fs/main1.c
Normal file
13
C13-Linux系统编程/fs/main1.c
Normal file
@@ -0,0 +1,13 @@
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
printf("Hello, World!\n");
|
||||
|
||||
return 0;
|
||||
/*
|
||||
* echo $?
|
||||
* 0
|
||||
*/
|
||||
}
|
||||
109
C13-Linux系统编程/fs/mydate.c
Normal file
109
C13-Linux系统编程/fs/mydate.c
Normal file
@@ -0,0 +1,109 @@
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include <string.h>
|
||||
#include <time.h>
|
||||
#include <unistd.h>
|
||||
|
||||
#define TIMESTRSIZE 1024
|
||||
#define FMTSTRSIZE 1024
|
||||
|
||||
/**
|
||||
* @brief mydate
|
||||
* @details
|
||||
* Usage:
|
||||
* mydate [-H 12|24] [-y 2|4] [-m] [-d] [-M] [-S]
|
||||
* Options:
|
||||
* -y: year 2位,4位
|
||||
* -m: month
|
||||
* -d: day
|
||||
* -H: hour 12小时制,24小时制
|
||||
* -M: minute
|
||||
* -S: second
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
time_t stamp;
|
||||
struct tm *tm;
|
||||
char timestr[TIMESTRSIZE];
|
||||
int c;
|
||||
char fmtstr[FMTSTRSIZE];
|
||||
fmtstr[0] = '\0';
|
||||
FILE *fp = stdout;
|
||||
|
||||
time(&stamp);
|
||||
tm = localtime(&stamp);
|
||||
|
||||
while (1)
|
||||
{
|
||||
//* 选项传参
|
||||
// c = getopt(argc, argv, "H:y:MSmd");
|
||||
|
||||
//* 加'-'，接收非选项传参
|
||||
c = getopt(argc, argv, "-H:y:MSmd");
|
||||
if (c < 0)
|
||||
break;
|
||||
|
||||
switch (c)
|
||||
{
|
||||
//* 非选项传参，返回1
|
||||
case 1:
|
||||
if (stdout == fp) //! 先入为主
|
||||
{
|
||||
fp = fopen(argv[optind - 1], "w");
|
||||
if (NULL == fp)
|
||||
{
|
||||
perror("fopen()");
|
||||
fp = stdout;
|
||||
}
|
||||
}
|
||||
break;
|
||||
|
||||
case 'H':
|
||||
if (0 == strcmp(optarg, "12"))
|
||||
strncat(fmtstr, "%I(%P) ", FMTSTRSIZE - 1);
|
||||
else if (0 == strcmp(optarg, "24"))
|
||||
strncat(fmtstr, "%H ", FMTSTRSIZE - 1);
|
||||
else
|
||||
fprintf(stderr,
|
||||
"Usage: %s [-H 12|24] [-y 2|4] [-m] [-d] [-M] [-S]\n",
|
||||
argv[0]);
|
||||
break;
|
||||
|
||||
case 'M': strncat(fmtstr, "%M ", FMTSTRSIZE - 1); break;
|
||||
|
||||
case 'S': strncat(fmtstr, "%S ", FMTSTRSIZE - 1); break;
|
||||
|
||||
case 'y':
|
||||
if (0 == strcmp(optarg, "2"))
|
||||
strncat(fmtstr, "%y ", FMTSTRSIZE - 1);
|
||||
else if (0 == strcmp(optarg, "4"))
|
||||
strncat(fmtstr, "%Y ", FMTSTRSIZE - 1);
|
||||
else
|
||||
fprintf(stderr,
|
||||
"Usage: %s [-H 12|24] [-y 2|4] [-m] [-d] [-M] [-S]\n",
|
||||
argv[0]);
|
||||
break;
|
||||
|
||||
case 'm': strncat(fmtstr, "%m ", FMTSTRSIZE - 1); break;
|
||||
|
||||
case 'd': strncat(fmtstr, "%d ", FMTSTRSIZE - 1); break;
|
||||
|
||||
default: break;
|
||||
}
|
||||
}
|
||||
|
||||
strncat(fmtstr, "\n", FMTSTRSIZE - 1);
|
||||
strftime(timestr, TIMESTRSIZE, fmtstr, tm);
|
||||
|
||||
fputs(timestr, fp);
|
||||
|
||||
if (fp != stdout)
|
||||
fclose(fp);
|
||||
|
||||
exit(0);
|
||||
}
|
||||
86
C13-Linux系统编程/fs/timelog.c
Normal file
86
C13-Linux系统编程/fs/timelog.c
Normal file
@@ -0,0 +1,86 @@
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include <time.h>
|
||||
#include <unistd.h>
|
||||
|
||||
#define FNAME "time.log"
|
||||
#define BUFSIZE 1024
|
||||
|
||||
/**
|
||||
* @brief 往文件里面输出时间戳
|
||||
* @details
|
||||
* 实例格式：2019-12-12 12:12:12
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
FILE *fp;
|
||||
time_t stamp;
|
||||
struct tm *tm;
|
||||
char buf[BUFSIZE];
|
||||
int count = 0;
|
||||
|
||||
fp = fopen(FNAME, "a+");
|
||||
if (fp == NULL)
|
||||
{
|
||||
perror("fopen()");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
while (fgets(buf, BUFSIZE, fp) != NULL)
|
||||
count++;
|
||||
|
||||
while (1)
|
||||
{
|
||||
stamp = time(NULL);
|
||||
|
||||
tm = localtime(&stamp);
|
||||
if (NULL == tm)
|
||||
{
|
||||
perror("localtime()");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
strftime(buf, BUFSIZE, "%Y-%m-%d %H:%M:%S", tm);
|
||||
|
||||
fprintf(fp, "%-4d%s\n", ++count, buf);
|
||||
|
||||
/*
|
||||
* 加了sleep(1)之后就没有输出？
|
||||
* 全缓冲
|
||||
* 因为缓冲区没有满，没有刷新到文件里面
|
||||
*/
|
||||
fflush(fp);
|
||||
|
||||
sleep(1);
|
||||
}
|
||||
|
||||
fclose(fp);
|
||||
exit(0);
|
||||
}
|
||||
|
||||
//! 最终效果
|
||||
// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ ./test
|
||||
// ^C
|
||||
// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ cat time.log
|
||||
// 1 2024-05-11 21:53:26
|
||||
// 2 2024-05-11 21:53:27
|
||||
// 3 2024-05-11 21:53:28
|
||||
// 4 2024-05-11 21:53:29
|
||||
// 5 2024-05-11 21:53:30
|
||||
// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ ./test
|
||||
// ^C
|
||||
// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ cat time.log
|
||||
// 1 2024-05-11 21:53:26
|
||||
// 2 2024-05-11 21:53:27
|
||||
// 3 2024-05-11 21:53:28
|
||||
// 4 2024-05-11 21:53:29
|
||||
// 5 2024-05-11 21:53:30
|
||||
// 6 2024-05-11 21:53:35
|
||||
// 7 2024-05-11 21:53:36
|
||||
// 8 2024-05-11 21:53:37
|
||||
// 9 2024-05-11 21:53:38
|
||||
29
C13-Linux系统编程/fs/username.c
Normal file
29
C13-Linux系统编程/fs/username.c
Normal file
@@ -0,0 +1,29 @@
|
||||
#include <pwd.h>
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
|
||||
/**
|
||||
* @brief 用user id获取用户名
|
||||
* @details
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
if (argc < 2)
|
||||
{
|
||||
fprintf(stderr, "Usage: %s <user id>\n", argv[0]);
|
||||
exit(1);
|
||||
}
|
||||
|
||||
struct passwd *pwdline;
|
||||
|
||||
pwdline = getpwuid(atoi(argv[1]));
|
||||
|
||||
puts(pwdline->pw_name);
|
||||
|
||||
exit(0);
|
||||
}
|
||||
Reference in New Issue
Block a user