linux class设置］自实现的 shell 命令行解释器
最编程
2024-04-02 20:25:57
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#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<string.h>
#include<stdlib.h>
#include<sys/wait.h>
#include<errno.h>
#define SIZE 100
#define COMMAND_SIZE 200
#define ZEOR '\0'
#define ARGV_NUM 32
#define SKIP " "
#define SkipPath(p) do{p+=strlen(p)-1; while(*p!='/'){p--;}}while(0)
char* gArgv[ARGV_NUM];//指令参数
char cwd[SIZE*2];//当前路径的环境变量键值对
int lastcode=0;
const char* GetUserName(){//获取环境变量中的值
const char* name=getenv("USER");
if(name==NULL){
return "None";
}
return name;
}
const char* GetHome(){//获取家目录
const char* home=getenv("HOME");
if(home==NULL){
return "/";
}
return home;
}
const char* GetHostHome(){//获取主机名
const char* hostname=getenv("HOSTNAME");
if(hostname==NULL){
return "None";
}
return hostname;
}
const char* GetCwd(){//获取当前路径
const char* cwd=getenv("PWD");
if(cwd==NULL){
return "None";
}
return cwd;
}
//输出命令行
void MakeCommandLineAndPrint(){
char line[SIZE];
const char* name=GetUserName();
const char* hostname=GetHostHome();
const char* cwd=GetCwd();
SkipPath(cwd);
snprintf(line,sizeof(line),"[%s@%s %s]> ",name,hostname,cwd=strlen(cwd)==1?"/":cwd+1);
printf("%s",line);
fflush(stdout);
}
//获取用户命令行
int GetUserCommand(char command[],size_t n){
char* s=fgets(command,n,stdin);
if(s==NULL)return -1;
command[strlen(command)-1]=ZEOR;
return (int)strlen(command);
}
//命令行分割,获取命令行参数列表
void SplitCommand(char command[],size_t n){
gArgv[0]=strtok(command,SKIP);
size_t index=1;
char* t=gArgv[0];
while(t!=NULL){
t=strtok(NULL,SKIP);
gArgv[index++]=t;
}
//size_t i=0;
//for(;i<index;i++){
// printf("%s\n",gArgv[i]);
//}
}
//cd内建命令
void Cd(){
const char* path=gArgv[1];
if(path==NULL){
path=GetHome();
}
//更新当前工作目录
chdir(path);//修改当前进程的工作路径
//更新环境变量
char t[SIZE*2];
getcwd(t,sizeof(t));
snprintf(cwd,sizeof(cwd),"PWD=%s",t);
putenv(cwd);
}
//查看是否是内建命令
int CheckBuiltIn(){
int yes=0;
const char* cmd=gArgv[0];
if(strcmp(cmd,"cd")==0){
yes=1;
Cd();
}
return yes;
}
// 处理创建子进程失败
void Die(){
exit(1);
}
//执行指令
void ExeCommand(){
pid_t id=fork();
if(id<0){
Die();
}
if(id==0){
//child
execvp(gArgv[0],gArgv);
exit(errno);
}else{
int status=0;
pid_t res=waitpid(id,&status,0);
if(res>0){
lastcode=WEXITSTATUS(status);//获取子进程退出码信息
if(WIFEXITED(status)){
if(lastcode!=0) printf("%s:%s:%d\n",gArgv[0],strerror(lastcode),lastcode);
}
}
}
}
int main(){
int quit=0;
while(!quit){
//1.输出一个命令行
MakeCommandLineAndPrint();
//2.获取用户命令
char command[COMMAND_SIZE];
int n= GetUserCommand(command,sizeof(command));
if(n<=0)return 1;//输入指令不合法
// printf("%s\n",command);
//3.命令行字符串分割
SplitCommand(command,sizeof(command));
//4.查看命令是否是内建命令
int flag=CheckBuiltIn();
if(flag)continue;
//5.执行指令
ExeCommand();
}
return 0;
}