文章目录
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- [5. 自主Shell命令行解释器](#5. 自主Shell命令行解释器)
5. 自主Shell命令行解释器
c
复制代码
[gsm@VM-4-3-centos myshell]$ touch myshell.cc
[gsm@VM-4-3-centos myshell]$ ll
total 0
-rw-rw-r-- 1 gsm gsm 0 Nov 26 14:00 myshell.cc
[gsm@VM-4-3-centos myshell]$ ls > Makefile
[gsm@VM-4-3-centos myshell]$ vim Makefile
[gsm@VM-4-3-centos myshell]$ cat Makefile
CC:=g++
myshell:myshell.cc
$(CC) -o $@ $^
.PHONY:clean
clean:
rm -f myshell
[gsm@VM-4-3-centos myshell]$ vim Makefile
[gsm@VM-4-3-centos myshell]$ cat Makefile
CC:=g++
myshell:myshell.cc
$(CC) -o $@ $^
.PHONY:clean
clean:
rm -f myshell
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc
[gsm@VM-4-3-centos myshell]$ ll
total 20
-rw-rw-r-- 1 gsm gsm 78 Nov 26 14:08 Makefile
-rwxrwxr-x 1 gsm gsm 8656 Nov 26 14:08 myshell
-rw-rw-r-- 1 gsm gsm 91 Nov 26 14:07 myshell.cc
[gsm@VM-4-3-centos myshell]$ make clean
rm -f myshell
[gsm@VM-4-3-centos myshell]$ ll
total 8
-rw-rw-r-- 1 gsm gsm 78 Nov 26 14:08 Makefile
-rw-rw-r-- 1 gsm gsm 91 Nov 26 14:07 myshell.cc
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$
[gsm@VM-4-3-centos myshell]$ clear
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
using namespace std;
const int basesize = 1024;
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
string pwd = getenv("PWD");
return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
int main()
{
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
printf("\n");
sleep(1);
//GetCommandLine(); // 2. 获取用户命令
//ParseCommandLine(); // 3. 分析命令
//ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
^C
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 8
-rw-rw-r-- 1 gsm gsm 78 Nov 26 14:08 Makefile
-rw-rw-r-- 1 gsm gsm 1584 Nov 26 15:34 myshell.cc
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
using namespace std;
const int basesize = 1024;
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
string pwd = getenv("PWD");
return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
return true;
}
int main()
{
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
printf("%s\n", command_buffer);
//ParseCommandLine(); // 3. 分析命令
//ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls
ls
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# pwd
pwd
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -a -l
ls -a -l
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -a -b -c -d
ls -a -b -c -d
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 8
-rw-rw-r-- 1 gsm gsm 78 Nov 26 14:08 Makefile
-rw-rw-r-- 1 gsm gsm 1786 Nov 26 15:54 myshell.cc
[gsm@VM-4-3-centos myshell]$ vim Makefile
[gsm@VM-4-3-centos myshell]$ cat Makefile
CC:=g++
myshell:myshell.cc
$(CC) -o $@ $^ -std=c++11
.PHONY:clean
clean:
rm -f myshell
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
// 全局的命令行参数表
char* gargv[argvnum];
int gargc = 0;
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
string pwd = getenv("PWD");
return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
if (strlen(command_buffer) == 0)
{
return false;
}
return true;
}
void ParseCommandLine(char command_buffer[], int len)
{
(void)len;
memset(gargv, 0, sizeof(gargv));
gargc = 0;
// "ls -a -l -n"
const char* sep = " ";
gargv[gargc++] = strtok(command_buffer, sep);
// =是刻意写的
while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
gargc--;
}
void debug()
{
printf("argc: %d\n", gargc);
for (int i = 0; gargv[i]; i++)
{
printf("argv[%d]: %s\n", i, gargv[i]);
}
}
int main()
{
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
//ls
//"ls -a -b -c -d"->"ls" "-a" "-b" "-c" "-d"
ParseCommandLine(command_buffer, strlen(command_buffer)); // 3. 分析命令
debug();
//ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc -std=c++11
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls
argc: 1
argv[0]: ls
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -a -l
argc: 3
argv[0]: ls
argv[1]: -a
argv[2]: -l
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -a --l
argc: 3
argv[0]: ls
argv[1]: -a
argv[2]: --l
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -a -l -a -c -d -ef -w
argc: 8
argv[0]: ls
argv[1]: -a
argv[2]: -l
argv[3]: -a
argv[4]: -c
argv[5]: -d
argv[6]: -ef
argv[7]: -w
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 8
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rw-rw-r-- 1 gsm gsm 2509 Nov 26 18:35 myshell.cc
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
// 全局的命令行参数表
char* gargv[argvnum];
int gargc = 0;
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
string pwd = getenv("PWD");
return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
if (strlen(command_buffer) == 0)
{
return false;
}
return true;
}
void ParseCommandLine(char command_buffer[], int len)
{
(void)len;
memset(gargv, 0, sizeof(gargv));
gargc = 0;
// "ls -a -l -n"
const char* sep = " ";
gargv[gargc++] = strtok(command_buffer, sep);
// =是刻意写的
while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
gargc--;
}
bool ExecuteCommand()
{
// 让子进程进行执行
pid_t id = fork();
if (id < 0)
{
return false;
}
if (id == 0)
{
// 子进程
// 1. 执行命令
execvp(gargv[0], gargv);
// 2. 退出
exit(1);
}
int status = 0;
pid_t rid = waitpid(id, &status, 0);
if (rid > 0)
{
// Do Nothing
return true;
}
return false;
}
int main()
{
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
//ls
//"ls -a -b -c -d"->"ls" "-a" "-b" "-c" "-d"
ParseCommandLine(command_buffer, strlen(command_buffer)); // 3. 分析命令
ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc -std=c++11
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls
Makefile myshell myshell.cc
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# pwd
/home/gsm/linux/112/lesson17/myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# top
top - 22:38:45 up 52 days, 7:22, 1 user, load average: 0.05, 0.33, 0.22
Tasks: 95 total, 1 running, 94 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.5 us, 0.5 sy, 0.0 ni, 99.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 2046500 total, 354892 free, 279176 used, 1412432 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 1569908 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
25273 root 20 0 1039700 121624 16576 S 1.0 5.9 536:07.77 YDService
1606 root 20 0 821564 17920 2844 S 0.7 0.9 696:26.99 barad_agent
1 root 20 0 43592 3640 2320 S 0.0 0.2 4:28.78 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.79 kthreadd
4 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H
6 root 20 0 0 0 0 S 0.0 0.0 0:42.62 ksoftirqd/0
7 root rt 0 0 0 0 S 0.0 0.0 0:19.78 migration/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh
9 root 20 0 0 0 0 S 0.0 0.0 9:47.79 rcu_sched
10 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 lru-add-drain
11 root rt 0 0 0 0 S 0.0 0.0 0:10.57 watchdog/0
12 root rt 0 0 0 0 S 0.0 0.0 0:08.56 watchdog/1
13 root rt 0 0 0 0 S 0.0 0.0 0:20.04 migration/1
14 root 20 0 0 0 0 S 0.0 0.0 0:40.55 ksoftirqd/1
16 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/1:0H
18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kdevtmpfs
19 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 netns
20 root 20 0 0 0 0 S 0.0 0.0 0:00.86 khungtaskd
21 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 writeback
22 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kintegrityd
23 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 bioset
24 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 bioset
25 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 bioset
26 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kblockd
27 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 md
28 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 edac-poller
29 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 watchdogd
35 root 20 0 0 0 0 S 0.0 0.0 0:01.05 kswapd0
36 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
37 root 39 19 0 0 0 S 0.0 0.0 0:04.38 khugepaged
38 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 crypto
46 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kthrotld
48 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kmpath_rdacd
49 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kaluad
50 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kpsmoused
51 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 ipv6_addrconf
65 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 deferwq
108 root 20 0 0 0 0 S 0.0 0.0 0:12.60 kauditd
200 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 iscsi_eh
259 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 ata_sff
262 root 20 0 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_0
263 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 scsi_tmf_0
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]#
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -l
total 24
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rwxrwxr-x 1 gsm gsm 14664 Nov 26 22:36 myshell
-rw-rw-r-- 1 gsm gsm 2824 Nov 26 22:36 myshell.cc
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -l -a
total 32
drwxrwxr-x 2 gsm gsm 4096 Nov 26 22:36 .
drwxrwxr-x 3 gsm gsm 4096 Nov 26 13:59 ..
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rwxrwxr-x 1 gsm gsm 14664 Nov 26 22:36 myshell
-rw-rw-r-- 1 gsm gsm 2824 Nov 26 22:36 myshell.cc
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# touch temp.txt
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -l -a
total 32
drwxrwxr-x 2 gsm gsm 4096 Nov 26 22:39 .
drwxrwxr-x 3 gsm gsm 4096 Nov 26 13:59 ..
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rwxrwxr-x 1 gsm gsm 14664 Nov 26 22:36 myshell
-rw-rw-r-- 1 gsm gsm 2824 Nov 26 22:36 myshell.cc
-rw-rw-r-- 1 gsm gsm 0 Nov 26 22:39 temp.txt
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# rm temp.txt
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls -a -l
total 32
drwxrwxr-x 2 gsm gsm 4096 Nov 26 22:40 .
drwxrwxr-x 3 gsm gsm 4096 Nov 26 13:59 ..
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rwxrwxr-x 1 gsm gsm 14664 Nov 26 22:36 myshell
-rw-rw-r-- 1 gsm gsm 2824 Nov 26 22:36 myshell.cc
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 8
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rw-rw-r-- 1 gsm gsm 3522 Nov 27 15:41 myshell.cc
[gsm@VM-4-3-centos myshell]$ man getcwd
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
const int envnum = 64;
// 全局的命令行参数表
char* gargv[argvnum];
int gargc = 0;
// 全局的当前shell工作路径
char pwd[basesize];
char pwdenv[basesize];
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
if (nullptr == getcwd(pwd, sizeof(pwd)))
{
return "None";
}
snprintf(pwdenv, sizeof(pwdenv), "PWD=%s", pwd);
putenv(pwdenv); // PWD=XXX
return pwd;
//string pwd = getenv("PWD");
//return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
if (strlen(command_buffer) == 0)
{
return false;
}
return true;
}
void ParseCommandLine(char command_buffer[], int len)
{
(void)len;
memset(gargv, 0, sizeof(gargv));
gargc = 0;
// "ls -a -l -n"
const char* sep = " ";
gargv[gargc++] = strtok(command_buffer, sep);
// =是刻意写的
while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
gargc--;
}
// 在shell中
// 有些命令，必须由子进程来执行
// 有些命令，不能由子进程执行，要由shell自己执行 --- 内建命令 built command
bool ExecuteCommand()
{
// 让子进程进行执行
pid_t id = fork();
if (id < 0)
{
return false;
}
if (id == 0)
{
// 子进程
// 1. 执行命令
execvp(gargv[0], gargv);
// 2. 退出
exit(1);
}
int status = 0;
pid_t rid = waitpid(id, &status, 0);
if (rid > 0)
{
// Do Nothing
return true;
}
return false;
}
// shell自己执行命令，本质是shell调用自己的函数
bool CheckiAndExecBuiltCommand()
{
if (strcmp(gargv[0], "cd") == 0)
{
// 内建命令
if (gargc == 2)
{
chdir(gargv[1]);
}
return true;
}
return false;
}
int main()
{
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
//ls
//"ls -a -b -c -d"->"ls" "-a" "-b" "-c" "-d"
ParseCommandLine(command_buffer, strlen(command_buffer)); // 3. 分析命令
if (CheckiAndExecBuiltCommand())
{
continue;
}
ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc -std=c++11
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# pwd
/home/gsm/linux/112/lesson17/myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17/myshell
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# cd ..
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17]# pwd
/home/gsm/linux/112/lesson17
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17]# cd /
[gsm@VM-4-3-centos /]# pwd
/
[gsm@VM-4-3-centos /]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 12
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rw-rw-r-- 1 gsm gsm 4331 Nov 27 16:55 myshell.cc
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
const int envnum = 64;
// 全局的命令行参数表
char* gargv[argvnum];
int gargc = 0;
// 我的系统的环境变量
char* genv[envnum];
// 全局的当前shell工作路径
char pwd[basesize];
char pwdenv[basesize];
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
if (nullptr == getcwd(pwd, sizeof(pwd)))
{
return "None";
}
snprintf(pwdenv, sizeof(pwdenv), "PWD=%s", pwd);
putenv(pwdenv); // PWD=XXX
return pwd;
//string pwd = getenv("PWD");
//return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
if (strlen(command_buffer) == 0)
{
return false;
}
return true;
}
void ParseCommandLine(char command_buffer[], int len)
{
(void)len;
memset(gargv, 0, sizeof(gargv));
gargc = 0;
// "ls -a -l -n"
const char* sep = " ";
gargv[gargc++] = strtok(command_buffer, sep);
// =是刻意写的
while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
gargc--;
}
// 在shell中
// 有些命令，必须由子进程来执行
// 有些命令，不能由子进程执行，要由shell自己执行 --- 内建命令 built command
bool ExecuteCommand()
{
// 让子进程进行执行
pid_t id = fork();
if (id < 0)
{
return false;
}
if (id == 0)
{
// 子进程
// 1. 执行命令
execvp(gargv[0], gargv);
// 2. 退出
exit(1);
}
int status = 0;
pid_t rid = waitpid(id, &status, 0);
if (rid > 0)
{
// Do Nothing
return true;
}
return false;
}
void AddEnv(const char* item)
{
int index = 0;
while (genv[index])
{
index++;
}
genv[index] = (char*)malloc(strlen(item) + 1);
strncpy(genv[index], item, strlen(item) + 1);
genv[++index] = nullptr;
}
// shell自己执行命令，本质是shell调用自己的函数
bool CheckiAndExecBuiltCommand()
{
if (strcmp(gargv[0], "cd") == 0)
{
// 内建命令
if (gargc == 2)
{
chdir(gargv[1]);
}
return true;
}
else if(strcmp(gargv[0], "export") == 0)
{
// export也是内建命令
if (gargc == 2)
{
AddEnv(gargv[1]);
}
return true;
}
else if (strcmp(gargv[0], "env") == 0)
{
for (int i = 0; genv[i]; i++)
{
printf("%s\n", genv[i]);
}
return true;
}
return false;
}
// 作为一个shell，获取环境变量应该从系统的配置来
// 我们今天就直接从父shell中获取环境变量
void InitEnv()
{
extern char** environ;
int index = 0;
while (environ[index])
{
genv[index] = (char*)malloc(strlen(environ[index]) + 1);
strncpy(genv[index], environ[index], strlen(environ[index]) + 1);
index++;
}
genv[index] = nullptr;
}
int main()
{
InitEnv();
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
//ls
//"ls -a -b -c -d"->"ls" "-a" "-b" "-c" "-d"
ParseCommandLine(command_buffer, strlen(command_buffer)); // 3. 分析命令
if (CheckiAndExecBuiltCommand())
{
continue;
}
ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc -std=c++11
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17/myshell
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# export HAHA=AAAAAAAAAA
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17/myshell
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
HAHA=AAAAAAAAAA
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# export hehe=BBBBBBBBBBBBBBB
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17/myshell
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
HAHA=AAAAAAAAAA
hehe=BBBBBBBBBBBBBBB
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 12
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rw-rw-r-- 1 gsm gsm 4740 Nov 27 18:20 myshell.cc
[gsm@VM-4-3-centos myshell]$ touch testenv.c
[gsm@VM-4-3-centos myshell]$ vim testenv.c
[gsm@VM-4-3-centos myshell]$ cat testenv.c
#include <stdio.h>
int main(int argc, char* argv[], char* env[])
{
for (int i = 0; i < argc; i++)
{
printf("argv[%d]: %s\n", i, argv[i]);
}
for (int i = 0; env[i]; i++)
{
printf("env[%d]: %s\n", i, env[i]);
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ gcc -o testenv testenv.c -std=c99
[gsm@VM-4-3-centos myshell]$ ./testenv
argv[0]: ./testenv
env[0]: XDG_SESSION_ID=95407
env[1]: HOSTNAME=VM-4-3-centos
env[2]: TERM=xterm
env[3]: SHELL=/bin/bash
env[4]: HISTSIZE=3000
env[5]: SSH_CLIENT=101.94.69.10 61355 22
env[6]: SSH_TTY=/dev/pts/0
env[7]: USER=gsm
env[8]: LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
env[9]: LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
env[10]: MAIL=/var/spool/mail/gsm
env[11]: PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
env[12]: PWD=/home/gsm/linux/112/lesson17/myshell
env[13]: LANG=en_US.utf8
env[14]: SHLVL=1
env[15]: HOME=/home/gsm
env[16]: LOGNAME=gsm
env[17]: SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
env[18]: LESSOPEN=||/usr/bin/lesspipe.sh %s
env[19]: PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
env[20]: XDG_RUNTIME_DIR=/run/user/1001
env[21]: HISTTIMEFORMAT=%F %T
env[22]: OLDPWD=/home/gsm/linux/112/lesson17
env[23]: _=./testenv
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
const int envnum = 64;
// 全局的命令行参数表
char* gargv[argvnum];
int gargc = 0;
// 我的系统的环境变量
char* genv[envnum];
// 全局的当前shell工作路径
char pwd[basesize];
char pwdenv[basesize];
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
if (nullptr == getcwd(pwd, sizeof(pwd)))
{
return "None";
}
snprintf(pwdenv, sizeof(pwdenv), "PWD=%s", pwd);
putenv(pwdenv); // PWD=XXX
return pwd;
//string pwd = getenv("PWD");
//return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
if (strlen(command_buffer) == 0)
{
return false;
}
return true;
}
void ParseCommandLine(char command_buffer[], int len)
{
(void)len;
memset(gargv, 0, sizeof(gargv));
gargc = 0;
// "ls -a -l -n"
const char* sep = " ";
gargv[gargc++] = strtok(command_buffer, sep);
// =是刻意写的
while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
gargc--;
}
// 在shell中
// 有些命令，必须由子进程来执行
// 有些命令，不能由子进程执行，要由shell自己执行 --- 内建命令 built command
bool ExecuteCommand()
{
// 让子进程进行执行
pid_t id = fork();
if (id < 0)
{
return false;
}
if (id == 0)
{
// 子进程
// 1. 执行命令
execvpe(gargv[0], gargv, genv);
// 2. 退出
exit(1);
}
int status = 0;
pid_t rid = waitpid(id, &status, 0);
if (rid > 0)
{
// Do Nothing
return true;
}
return false;
}
void AddEnv(const char* item)
{
int index = 0;
while (genv[index])
{
index++;
}
genv[index] = (char*)malloc(strlen(item) + 1);
strncpy(genv[index], item, strlen(item) + 1);
genv[++index] = nullptr;
}
// shell自己执行命令，本质是shell调用自己的函数
bool CheckiAndExecBuiltCommand()
{
if (strcmp(gargv[0], "cd") == 0)
{
// 内建命令
if (gargc == 2)
{
chdir(gargv[1]);
}
return true;
}
else if(strcmp(gargv[0], "export") == 0)
{
// export也是内建命令
if (gargc == 2)
{
AddEnv(gargv[1]);
}
return true;
}
else if (strcmp(gargv[0], "env") == 0)
{
for (int i = 0; genv[i]; i++)
{
printf("%s\n", genv[i]);
}
return true;
}
return false;
}
// 作为一个shell，获取环境变量应该从系统的配置来
// 我们今天就直接从父shell中获取环境变量
void InitEnv()
{
extern char** environ;
int index = 0;
while (environ[index])
{
genv[index] = (char*)malloc(strlen(environ[index]) + 1);
strncpy(genv[index], environ[index], strlen(environ[index]) + 1);
index++;
}
genv[index] = nullptr;
}
int main()
{
InitEnv();
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
//ls
//"ls -a -b -c -d"->"ls" "-a" "-b" "-c" "-d"
ParseCommandLine(command_buffer, strlen(command_buffer)); // 3. 分析命令
if (CheckiAndExecBuiltCommand())
{
continue;
}
ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc -std=c++11
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17/myshell
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ./testenv
argv[0]: ./testenv
env[0]: XDG_SESSION_ID=95407
env[1]: HOSTNAME=VM-4-3-centos
env[2]: TERM=xterm
env[3]: SHELL=/bin/bash
env[4]: HISTSIZE=3000
env[5]: SSH_CLIENT=101.94.69.10 61355 22
env[6]: SSH_TTY=/dev/pts/0
env[7]: USER=gsm
env[8]: LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
env[9]: LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
env[10]: MAIL=/var/spool/mail/gsm
env[11]: PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
env[12]: PWD=/home/gsm/linux/112/lesson17/myshell
env[13]: LANG=en_US.utf8
env[14]: SHLVL=1
env[15]: HOME=/home/gsm
env[16]: LOGNAME=gsm
env[17]: SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
env[18]: LESSOPEN=||/usr/bin/lesspipe.sh %s
env[19]: PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
env[20]: XDG_RUNTIME_DIR=/run/user/1001
env[21]: HISTTIMEFORMAT=%F %T
env[22]: OLDPWD=/home/gsm/linux/112/lesson17
env[23]: _=./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# export HAHA=aaaaaaaaaaaaaaaa
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17/myshell
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=./myshell
HAHA=aaaaaaaaaaaaaaaa
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ./testenv
argv[0]: ./testenv
env[0]: XDG_SESSION_ID=95407
env[1]: HOSTNAME=VM-4-3-centos
env[2]: TERM=xterm
env[3]: SHELL=/bin/bash
env[4]: HISTSIZE=3000
env[5]: SSH_CLIENT=101.94.69.10 61355 22
env[6]: SSH_TTY=/dev/pts/0
env[7]: USER=gsm
env[8]: LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
env[9]: LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
env[10]: MAIL=/var/spool/mail/gsm
env[11]: PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
env[12]: PWD=/home/gsm/linux/112/lesson17/myshell
env[13]: LANG=en_US.utf8
env[14]: SHLVL=1
env[15]: HOME=/home/gsm
env[16]: LOGNAME=gsm
env[17]: SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
env[18]: LESSOPEN=||/usr/bin/lesspipe.sh %s
env[19]: PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
env[20]: XDG_RUNTIME_DIR=/run/user/1001
env[21]: HISTTIMEFORMAT=%F %T
env[22]: OLDPWD=/home/gsm/linux/112/lesson17
env[23]: _=./myshell
env[24]: HAHA=aaaaaaaaaaaaaaaa
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 48
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rwxrwxr-x 1 gsm gsm 19448 Nov 27 18:55 myshell
-rw-rw-r-- 1 gsm gsm 4747 Nov 27 18:55 myshell.cc
-rwxrwxr-x 1 gsm gsm 8360 Nov 27 18:45 testenv
-rw-rw-r-- 1 gsm gsm 268 Nov 27 18:45 testenv.c
[gsm@VM-4-3-centos myshell]$ a=100
[gsm@VM-4-3-centos myshell]$ echo $a
100
[gsm@VM-4-3-centos myshell]$ env
XDG_SESSION_ID=95407
HOSTNAME=VM-4-3-centos
TERM=xterm
SHELL=/bin/bash
HISTSIZE=3000
SSH_CLIENT=101.94.69.10 61355 22
SSH_TTY=/dev/pts/0
USER=gsm
LD_LIBRARY_PATH=:/home/gsm/.VimForCpp/vim/bundle/YCM.so/el7.x86_64
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
MAIL=/var/spool/mail/gsm
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/gsm/.local/bin:/home/gsm/bin
PWD=/home/gsm/linux/112/lesson17/myshell
LANG=en_US.utf8
SHLVL=1
HOME=/home/gsm
LOGNAME=gsm
SSH_CONNECTION=101.94.69.10 61355 10.0.4.3 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"
XDG_RUNTIME_DIR=/run/user/1001
HISTTIMEFORMAT=%F %T
OLDPWD=/home/gsm/linux/112/lesson17
_=/usr/bin/env
[gsm@VM-4-3-centos myshell]$ ls adfafag
ls: cannot access adfafag: No such file or directory
[gsm@VM-4-3-centos myshell]$ echo $?
2
[gsm@VM-4-3-centos myshell]$ echo $?
0
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
const int envnum = 64;
// 全局的命令行参数表
char* gargv[argvnum];
int gargc = 0;
// 全局的变量
int lastcode = 0;
// 我的系统的环境变量
char* genv[envnum];
// 全局的当前shell工作路径
char pwd[basesize];
char pwdenv[basesize];
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
if (nullptr == getcwd(pwd, sizeof(pwd)))
{
return "None";
}
snprintf(pwdenv, sizeof(pwdenv), "PWD=%s", pwd);
putenv(pwdenv); // PWD=XXX
return pwd;
//string pwd = getenv("PWD");
//return pwd.empty() ? "None": pwd;
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), GetPwd().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
if (strlen(command_buffer) == 0)
{
return false;
}
return true;
}
void ParseCommandLine(char command_buffer[], int len)
{
(void)len;
memset(gargv, 0, sizeof(gargv));
gargc = 0;
// "ls -a -l -n"
const char* sep = " ";
gargv[gargc++] = strtok(command_buffer, sep);
// =是刻意写的
while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
gargc--;
}
// 在shell中
// 有些命令，必须由子进程来执行
// 有些命令，不能由子进程执行，要由shell自己执行 --- 内建命令 built command
bool ExecuteCommand()
{
// 让子进程进行执行
pid_t id = fork();
if (id < 0)
{
return false;
}
if (id == 0)
{
// 子进程
// 1. 执行命令
execvpe(gargv[0], gargv, genv);
// 2. 退出
exit(1);
}
int status = 0;
pid_t rid = waitpid(id, &status, 0);
if (rid > 0)
{
if (WIFEXITED(status))
{
lastcode = WEXITSTATUS(status);
}
else
{
lastcode = 100;
}
return true;
}
return false;
}
void AddEnv(const char* item)
{
int index = 0;
while (genv[index])
{
index++;
}
genv[index] = (char*)malloc(strlen(item) + 1);
strncpy(genv[index], item, strlen(item) + 1);
genv[++index] = nullptr;
}
// shell自己执行命令，本质是shell调用自己的函数
bool CheckiAndExecBuiltCommand()
{
if (strcmp(gargv[0], "cd") == 0)
{
// 内建命令
if (gargc == 2)
{
chdir(gargv[1]);
lastcode = 0;
}
else
{
lastcode = 1;
}
return true;
}
else if(strcmp(gargv[0], "export") == 0)
{
// export也是内建命令
if (gargc == 2)
{
AddEnv(gargv[1]);
lastcode = 0;
}
else
{
lastcode = 2;
}
return true;
}
else if (strcmp(gargv[0], "env") == 0)
{
for (int i = 0; genv[i]; i++)
{
printf("%s\n", genv[i]);
}
lastcode = 0;
return true;
}
else if (strcmp(gargv[0], "echo") == 0)
{
if (gargc == 2)
{
// echo $?
// echo $PATH
// echo hello
if (gargv[1][0] == '$')
{
if (gargv[1][1] == '?')
{
printf("%d\n", lastcode);
lastcode = 0;
}
}
else
{
printf("%s\n", gargv[1]);
lastcode = 0;
}
}
else
{
lastcode = 3;
}
return true;
}
return false;
}
// 作为一个shell，获取环境变量应该从系统的配置来
// 我们今天就直接从父shell中获取环境变量
void InitEnv()
{
extern char** environ;
int index = 0;
while (environ[index])
{
genv[index] = (char*)malloc(strlen(environ[index]) + 1);
strncpy(genv[index], environ[index], strlen(environ[index]) + 1);
index++;
}
genv[index] = nullptr;
}
int main()
{
InitEnv();
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
//ls
//"ls -a -b -c -d"->"ls" "-a" "-b" "-c" "-d"
ParseCommandLine(command_buffer, strlen(command_buffer)); // 3. 分析命令
if (CheckiAndExecBuiltCommand())
{
continue;
}
ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc -std=c++11
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls
Makefile myshell myshell.cc testenv testenv.c
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# echo $?
0
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# ls asdfsfs
ls: cannot access asdfsfs: No such file or directory
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# echo $?
2
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# echo $?
0
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# echo hello
hello
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# echo $?
0
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# export
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# echo $?
2
[gsm@VM-4-3-centos /home/gsm/linux/112/lesson17/myshell]# echo $?
0
c
复制代码
[gsm@VM-4-3-centos myshell]$ ll
total 28
-rw-rw-r-- 1 gsm gsm 89 Nov 26 17:16 Makefile
-rw-rw-r-- 1 gsm gsm 5706 Nov 28 22:26 myshell.cc
-rwxrwxr-x 1 gsm gsm 8360 Nov 27 18:45 testenv
-rw-rw-r-- 1 gsm gsm 268 Nov 27 18:45 testenv.c
[gsm@VM-4-3-centos myshell]$ vim myshell.cc
[gsm@VM-4-3-centos myshell]$ cat myshell.cc
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
const int envnum = 64;
// 全局的命令行参数表
char* gargv[argvnum];
int gargc = 0;
// 全局的变量
int lastcode = 0;
// 我的系统的环境变量
char* genv[envnum];
// 全局的当前shell工作路径
char pwd[basesize];
char pwdenv[basesize];
string GetUserName()
{
string name = getenv("USER");
return name.empty() ? "None" : name;
}
string GetHostName()
{
string hostname = getenv("HOSTNAME");
return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
if (nullptr == getcwd(pwd, sizeof(pwd)))
{
return "None";
}
snprintf(pwdenv, sizeof(pwdenv), "PWD=%s", pwd);
putenv(pwdenv); // PWD=XXX
return pwd;
//string pwd = getenv("PWD");
//return pwd.empty() ? "None": pwd;
}
string LastDir()
{
string curr = GetPwd();
if (curr == "/" || curr == "None")
{
return curr;
}
// /home/gsm/XXX
size_t pos = curr.rfind("/");
if (pos == std::string::npos)
{
return curr;
}
return curr.substr(pos + 1);
}
string MakeCommandLine()
{
// [gsm@VM-4-3-centos myshell]$
char command_line[basesize];
snprintf(command_line, basesize, "[%s@%s %s]# ",\
GetUserName().c_str(), GetHostName().c_str(), LastDir().c_str());
return command_line;
}
void PrintCommandLine()
{
printf("%s", MakeCommandLine().c_str());
fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size)
{
// 我们认为：我们要将用户输入的命令行，当作一个完整的字符串
// "ls -a -l -n"
char* result = fgets(command_buffer, size, stdin);
if (!result)
{
return false;
}
// 输入abcde5个字符
// 数组中实际存放了6个字符，因为还有一个回车键
// 我们需要一个纯净的字符串，不想要这个'\n'
command_buffer[strlen(command_buffer) - 1] = 0;
if (strlen(command_buffer) == 0)
{
return false;
}
return true;
}
void ParseCommandLine(char command_buffer[], int len)
{
(void)len;
memset(gargv, 0, sizeof(gargv));
gargc = 0;
// "ls -a -l -n"
const char* sep = " ";
gargv[gargc++] = strtok(command_buffer, sep);
// =是刻意写的
while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
gargc--;
}
// 在shell中
// 有些命令，必须由子进程来执行
// 有些命令，不能由子进程执行，要由shell自己执行 --- 内建命令 built command
bool ExecuteCommand()
{
// 让子进程进行执行
pid_t id = fork();
if (id < 0)
{
return false;
}
if (id == 0)
{
// 子进程
// 1. 执行命令
execvpe(gargv[0], gargv, genv);
// 2. 退出
exit(1);
}
int status = 0;
pid_t rid = waitpid(id, &status, 0);
if (rid > 0)
{
if (WIFEXITED(status))
{
lastcode = WEXITSTATUS(status);
}
else
{
lastcode = 100;
}
return true;
}
return false;
}
void AddEnv(const char* item)
{
int index = 0;
while (genv[index])
{
index++;
}
genv[index] = (char*)malloc(strlen(item) + 1);
strncpy(genv[index], item, strlen(item) + 1);
genv[++index] = nullptr;
}
// shell自己执行命令，本质是shell调用自己的函数
bool CheckiAndExecBuiltCommand()
{
if (strcmp(gargv[0], "cd") == 0)
{
// 内建命令
if (gargc == 2)
{
chdir(gargv[1]);
lastcode = 0;
}
else
{
lastcode = 1;
}
return true;
}
else if(strcmp(gargv[0], "export") == 0)
{
// export也是内建命令
if (gargc == 2)
{
AddEnv(gargv[1]);
lastcode = 0;
}
else
{
lastcode = 2;
}
return true;
}
else if (strcmp(gargv[0], "env") == 0)
{
for (int i = 0; genv[i]; i++)
{
printf("%s\n", genv[i]);
}
lastcode = 0;
return true;
}
else if (strcmp(gargv[0], "echo") == 0)
{
if (gargc == 2)
{
// echo $?
// echo $PATH
// echo hello
if (gargv[1][0] == '$')
{
if (gargv[1][1] == '?')
{
printf("%d\n", lastcode);
lastcode = 0;
}
}
else
{
printf("%s\n", gargv[1]);
lastcode = 0;
}
}
else
{
lastcode = 3;
}
return true;
}
return false;
}
// 作为一个shell，获取环境变量应该从系统的配置来
// 我们今天就直接从父shell中获取环境变量
void InitEnv()
{
extern char** environ;
int index = 0;
while (environ[index])
{
genv[index] = (char*)malloc(strlen(environ[index]) + 1);
strncpy(genv[index], environ[index], strlen(environ[index]) + 1);
index++;
}
genv[index] = nullptr;
}
int main()
{
InitEnv();
char command_buffer[basesize];
while (true)
{
PrintCommandLine(); // 1. 命令行提示符
// command_buffer -> output
if (!GetCommandLine(command_buffer, basesize)) // 2. 获取用户命令
{
continue;
}
//ls
//"ls -a -b -c -d"->"ls" "-a" "-b" "-c" "-d"
ParseCommandLine(command_buffer, strlen(command_buffer)); // 3. 分析命令
if (CheckiAndExecBuiltCommand())
{
continue;
}
ExecuteCommand(); // 4. 执行命令
}
return 0;
}
[gsm@VM-4-3-centos myshell]$ make
g++ -o myshell myshell.cc -std=c++11
[gsm@VM-4-3-centos myshell]$ ./myshell
[gsm@VM-4-3-centos myshell]# cd /
[gsm@VM-4-3-centos /]# pwd
/
[gsm@VM-4-3-centos /]# cd /home/gsm
[gsm@VM-4-3-centos gsm]# pwd
/home/gsm
[gsm@VM-4-3-centos gsm]# cd linux
[gsm@VM-4-3-centos linux]# pwd
/home/gsm/linux
[gsm@VM-4-3-centos linux]# cd 112
[gsm@VM-4-3-centos 112]# pwd
/home/gsm/linux/112
[gsm@VM-4-3-centos 112]# cd /
[gsm@VM-4-3-centos /]# pwd
/