my_shell简单实现
实现功能
实现 管道（也就是 | ）
实现 输入输出重定向(<> >>)
实现 后台运行
实现 内建命令（cd ）
屏蔽一些信号（如ctrl + c 不能终止）
通过设置环境变量 可以直接使用 (在任意地方都可以运行你的shell)
界面美观
实现 tab补全
实现内置命令history
注意
gcc 编译时需要添加动态库-lreadline
vscode x修改配置文件 task.json
"args": [
"${file}",
"-o", // 指定输出文件名，不加该参数则默认输出a.exe，Linux下默认a.out
"${fileDirname}/${fileBasenameNoExtension}.out",
"-g", // 生成和调试有关的信息
"-Wall", // 开启额外警告
"-static-libgcc", // 静态链接libgcc，一般都会加上
//***在这里添加动态库***//
"-lreadline",
"-std=gnu11", // 要用的语言标准，根据自己的需要修改。c++可用c++14
总结
my_shell这部分实现还是比较简单，过程中要注意多进程无法用vscode直接调试，需要修改配置文件，注意理清功能分代码。
全部代码
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <dirent.h>
#include <signal.h>
#include <readline/readline.h>
#include <readline/history.h>
#define normal 0
#define output 1
#define input 2
#define grep 3
//本程序只能支持重定向输入，输出或管道命令的一种
void history();
void get_can(char *buf); //识别，读取判断
void explain_can(char *buf, int *nums, char can[100][256]); //解析参数
void do_can(int nums, char can[100][256]); //调用命令
int find_can(char *path); //寻找命令中的程序
void get_can(char *buf)
{
if (strcmp(buf, "exit") == 0 || strcmp(buf, "logout") == 0)
exit(0);
if (strlen(buf) > 256)
{
printf("输入指令过长，退出程序\n");
exit(1);
}
if(strcmp(buf,"history")==0)
history();
}
void history()
{
int i = 0;
HIST_ENTRY ** his;
his = history_list();
while(his[i] != NULL)
{
printf("%s\n", his[i]->line);
i++;
}
}
void explain_can(char *buf, int *nums, char can[100][256])
{
int j = 0;
for (int i = 0; i < strlen(buf); i++)
{
if (buf[i] == ' ')
{
can[*nums - 1][j] = '\0';
(*nums)++;
j = 0;
}
else
{
can[*nums - 1][j] = buf[i];
j++;
}
can[*nums - 1][j] = '\0';
}
}
void do_can(int nums, char can[100][256])
{
char *arg[nums + 1];
char *argnext[nums + 1];
int flag = 0;
int background = 0;
int fuhao = 0;
char *file = "";
pid_t pid;
int status;
int fd;
if(strcmp(can[0],"cd")==0)
{
//strcpy(can[0],"chdir");
if(chdir(can[1])<0)
printf("cd: no such file or directory:%s\n",can[1]);
return;
}
for (int i = 0; i < nums; i++)
{
arg[i] = (char *)can[i];
if (i == nums - 1)
arg[i + 1] = NULL;
if (strcmp(arg[i], "&") == 0)
{
if (i == nums - 1)
{
background = 1;
arg[i] = NULL;
}
else
{
printf("wrong input\n");
exit(1);
}
}
}
for (int i = 0; i < nums; i++)
{
if (strcmp(can[i], ">") == 0)
{
fuhao = output;
flag++;
}
if (strcmp(can[i], "<") == 0)
{
fuhao = input;
flag++;
}
if (strcmp(can[i], "|") == 0)
{
fuhao = grep;
flag++;
}
}
if (flag > 1)
{
printf("wrong input,the program can use one symbol\n");
exit(0);
}
if (fuhao == output)
{
for (int i = 0; i < nums; i++)
{
if (strcmp(arg[i], ">") == 0)
{
file = can[i + 1];
arg[i] = NULL;
break;
}
}
}
if (fuhao == input)
{
for (int i = 0; i < nums; i++)
{
if (strcmp(arg[i], "<") == 0)
{
file = arg[i + 1];
arg[i] = NULL;
break;
}
}
}
if (fuhao == grep)
{
int j;
for (int i = 0; i < nums; i++)
{
if (strcmp(arg[i], "|") == 0)
{
arg[i] = NULL;
int t = i;
for (j = 0; j < nums - i; j++)
{
argnext[j] = arg[++t];
}
break;
}
}
}
if ((pid = fork()) < 0)
{
printf("frok1 wrong\n");
return;
}
switch (fuhao)
{
case normal:
if (pid == 0)
{
if (!find_can(arg[0]))
{
printf("can not find %s file\n", arg[0]);
}
execvp(arg[0], arg);
exit(0);
}
break;
case output:
if (pid == 0)
{
if (!find_can(arg[0]))
{
printf("can not find %s file\n", arg[0]);
}
fd = (open(file, O_RDWR | O_CREAT | O_TRUNC, 0644));
dup2(fd, 1);
execvp(arg[0], arg);
exit(0);
}
break;
case input:
if (pid == 0)
{
if (!find_can(arg[0]))
{
printf("can not find %s file\n", arg[0]);
}
fd = (open(file, O_RDONLY, 0644));
dup2(fd, 2);
execvp(arg[0], arg);
exit(0);
}
break;
case grep:
if (pid == 0)
{
int fd2;
int status2;
pid_t pid2;
if ((pid2 = fork()) < 0)
{
printf("frok2 wrong\n");
return;
}
else if (pid2 == 0)
{
if (!find_can(arg[0]))
{
printf("can not find %s file\n", arg[0]);
}
fd2 = (open("/tmp/middlefile", O_WRONLY | O_CREAT | O_TRUNC, 0644));
dup2(fd, 1);
execvp(arg[0], arg);
exit(0);
}
if (waitpid(pid2, &status2, 0) == -1)
printf("wait for child progress error");
if (!find_can(argnext[0]))
{
printf("can not find %s file\n", arg[0]);
}
fd2 = (open("/tmp/middlefile", O_RDONLY, 0644));
dup2(fd, 2);
execvp(argnext[0], argnext);
if (remove("/tmp/middlefile") == -1)
printf("remove error\n");
exit(0);
}
break;
}
if (background != 1)
{
if (waitpid(pid, &status, 0) == -1)
printf("wait fork child progress error\n");
}
else
{
printf("process id is %d\n", pid);
return;
}
}
int find_can(char *path)
{
DIR *dp;
struct dirent *dir;
char *file[] = {
"./", "/bin", "/usr/bin", NULL};
if (strncmp(path, "./", 2) == 0)
path = path + 2;
int i = 0;
while (file[i] != NULL)
{
if ((dp = opendir(file[i])) == NULL)
printf(" can not open /bin\n");
while ((dir = readdir(dp)) != NULL)
{
if (strcmp(dir->d_name, path) == 0)
{
closedir(dp);
return 1;
}
}
closedir(dp);
i++;
}
return 0;
}
int main()
{
char *buf = NULL;
//buf = malloc(sizeof(char) * 256);
int nums;
char can[100][256];
while (1)
{
signal(SIGINT, SIG_IGN); //忽视信号处理，防止ctrl c杀苏
for (int i = 0; i < 100; i++)
can[i][0] = '\0';
if(buf!=NULL)
memset(buf, 0, 256);
nums = 1;
read_history(NULL);
buf=readline("my_shell$$");
add_history(buf);
write_history(NULL);
get_can(buf);
explain_can(buf, &nums, can);
do_can(nums, can);
if (buf != NULL)
{
free(buf);
buf = NULL;
}
}
return 0;
}