6. 贯穿案例2：mini shell（1）
【阶段性任务】实现cd、pwd和quit命令
//job.h
#ifndef __JOB_H__
#define __JOB_H__ //接收命令行参数
typedef struct
{
char** args; //对应于主函数中的char* argv[]参数（含进程名本身）
}Program; //命令行中可以包含多个程序（命令），如
//#date;ls -l，单个或多个命令通过cmd传入Job结构体中
typedef struct
{
char* cmd; //单条命令或多条命令(用分号隔开）
int progs_num; //作业中包含程序的数量
Program* progs; //各个程序的命令行参数
}Job; //创建作业
extern Job* create_job(char* cmd);
//销毁作业
extern void destroy_job(Job* job);
//创建进程（命令）
extern Program* create_program(char** arg);
//销毁进程（命令）
extern void destroy_program(Program* prog);
//将命令加入作业中
extern int add_program(Job* job, Program* prog); #endif
//job.c
#include "job.h"
#include <malloc.h>
#include <assert.h>
#include <string.h> //创建作业
Job* create_job(char* cmd)
{
Job* job = (Job*)malloc(sizeof(Job));
assert( job != NULL); job->cmd = (char*)malloc(sizeof(char) * strlen(cmd));
assert(job->cmd != NULL);
strcpy(job->cmd, cmd); job->progs_num = ;
job->progs = NULL; return job;
} //销毁作业
void destroy_job(Job* job)
{
assert(job != NULL);
free(job->progs);
free(job->cmd);
free(job);
} //arg格式：command arg0 arg1 ==> 返回3
static int arg_num(char** arg)
{
int ret = ;
char* start = arg[]; while(start != NULL){
start = arg[++ret];
} return ret;
} //创建进程（命令）
Program* create_program(char** arg)
{
Program* prog = (Program*)malloc(sizeof(Program));
assert(prog != NULL); int counter = arg_num(arg);
prog->args = (char**)calloc(counter + , sizeof(char*)); //以NULL结尾 int i = ;
for(i=; i< counter; i++){
int len = strlen(arg[i]);
prog->args[i] = (char*)malloc(len);
assert(prog->args[i] != NULL); strcpy(prog->args[i], arg[i]);
} prog->args[i] = NULL; //指针数组，以NULL结尾 return prog;
} //销毁进程（命令）
void destroy_program(Program* prog)
{
assert(prog != NULL); int i = ;
while(prog->args[i] != NULL)
{
free(prog->args[i++]);
} free(prog->args);
free(prog);
} //将命令加入作业中
int add_program(Job* job, Program* prog)
{
//重新申请一片空间以增加一条命令进来，放入job->progs中
Program* ps = (Program*)malloc(sizeof(Program) * (job->progs_num + ));
memcpy(ps, job->progs, job->progs_num * sizeof(Program)); ps[job->progs_num++] = *prog;//将新的进程（命令）加入进来 free(job->progs); //释放旧的程序（命令）组
job->progs = ps; return job->progs_num - ; //返回新命令的索引号
}
//mshell.c
#include "job.h"
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#include <assert.h> char* prompt = "mshell> "; //命令行的提示符
#define MAX_COMMAND_LEN 256 //命令行最多的字符数 //cd命令
void cd_fun(Program* prog)
{
if(chdir(prog->args[]) < ){
perror("cd error");
}
} //pwd命令
void pwd_fun(Program* prog)
{
char buffer[];
memset(buffer, , sizeof(buffer)); if(getcwd(buffer, sizeof(buffer)) == NULL){
perror("pwd error");
} printf("%s\n", buffer);
} //分析命令所带的参数（含进程名本身）
void split_cmd(Job* job, char* arguments)
{
char** args = (char**)malloc(MAX_COMMAND_LEN * sizeof(char*));
assert( args != NULL); char* cmd = strtok(arguments, " "); args[] = (char*)malloc(strlen(cmd) * sizeof(char)); //命令本身
strcpy(args[], cmd); int i = ;
char* s = NULL;
while((s = strtok(NULL, " ")) != NULL){ //将参数分隔出来
args[i] = (char*)malloc(strlen(s) * sizeof(char));
strcpy(args[i++], s);
} //根据args创建一个Program
Program* prog = create_program(args);
add_program(job, prog); int j = ;
for(j=; j < i; j++){
free(args[j]);
} free(args);
} //多条命令的解析
void parse_cmd(Job* job, char* line)
{
char buff [MAX_COMMAND_LEN]; //以“;”号分隔多条命令
char* pos = line;
char* start = line;
int count = ;
while( start < (line + strlen(line)) ){
memset(buff, , sizeof(buff));
if((pos = strchr(pos, ';')) == NULL)
{
pos = line + strlen(line);
} count = pos-start;
if(count > ){
memcpy(buff, start, count);
split_cmd(job, buff);
}
start = ++pos;
}
} //执行命令
void execute_cmd(Job* job)
{
int i = ;
for(i=; i<job->progs_num; i++)
{
//cd命令
if(!strcmp(job->progs[i].args[], "cd")){
cd_fun(&job->progs[i]);
} //pwd命令
if(!strcmp(job->progs[i].args[], "pwd")){
pwd_fun(&job->progs[i]);
} //quit命令
if(!strcmp(job->progs[i].args[], "quit")){
exit();
return;
}
}
} int main(int argc, char* argv[])
{
char buffer[MAX_COMMAND_LEN];
memset(buffer, , MAX_COMMAND_LEN); ssize_t size = strlen(prompt) * sizeof(char);
write(STDOUT_FILENO, prompt, size); ssize_t len = ;
while(){
len = read(STDIN_FILENO, buffer, MAX_COMMAND_LEN);
buffer[len -] = ; //以NULL结尾 if(strlen(buffer) > ){
Job* job = create_job(buffer); //解析命令
parse_cmd(job, buffer);
//执行命令
execute_cmd(job); destroy_job(job);
} write(STDOUT_FILENO, prompt, size);
memset(buffer, , MAX_COMMAND_LEN);
} return ;
}