execute.c

linux下的简单的shell解释器

#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>
#include <math.h>
#include <errno.h>
#include <signal.h>
#include <stddef.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <sys/termios.h>

#include "global.h"

int goon = 0, ingnore = 0;       //用于设置signal信号量
char *envPath[10], cmdBuff[40];  //外部命令的存放路径及读取外部命令的缓冲空间
History history;                 //历史命令
Job *head = NULL;                //作业头指针
pid_t fgPid;                     //当前前台作业的进程号

/*******************************************************
                  工具以及辅助方法
********************************************************/
/*判断命令是否存在*/
int exists(char *cmdFile){
    int i = 0;
    if((cmdFile[0] == '/' || cmdFile[0] == '.') && access(cmdFile, F_OK) == 0){ //命令在当前目录
        strcpy(cmdBuff, cmdFile);
        return 1;
    }else{  //查找ysh.conf文件中指定的目录，确定命令是否存在
        while(envPath[i] != NULL){ //查找路径已在初始化时设置在envPath[i]中
            strcpy(cmdBuff, envPath[i]);
            strcat(cmdBuff, cmdFile);
            
            if(access(cmdBuff, F_OK) == 0){ //命令文件被找到
                return 1;
            }
            
            i++;
        }
    }
    
    return 0; 
}

/*将字符串转换为整型的Pid*/
int str2Pid(char *str, int start, int end){
    int i, j;
    char chs[20];
    
    for(i = start, j= 0; i < end; i++, j++){
        if(str[i] < '0' || str[i] > '9'){
            return -1;
        }else{
            chs[j] = str[i];
        }
    }
    chs[j] = '\0';
    
    return atoi(chs);
}

/*调整部分外部命令的格式*/
void justArgs(char *str){
    int i, j, len;
    len = strlen(str);
    
    for(i = 0, j = -1; i < len; i++){
        if(str[i] == '/'){
            j = i;
        }
    }

    if(j != -1){ //找到符号'/'
        for(i = 0, j++; j < len; i++, j++){
            str[i] = str[j];
        }
        str[i] = '\0';
    }
}

/*设置goon*/
void setGoon(){
    goon = 1;
}

/*释放环境变量空间*/
void release(){
    int i;
    for(i = 0; strlen(envPath[i]) > 0; i++){
        free(envPath[i]);
    }
}

/*******************************************************
                  信号以及jobs相关
********************************************************/
/*添加新的作业*/
Job* addJob(pid_t pid){
    Job *now = NULL, *last = NULL, *job = (Job*)malloc(sizeof(Job));
    
	//初始化新的job
    job->pid = pid;
    strcpy(job->cmd, inputBuff);
    strcpy(job->state, RUNNING);
    job->next = NULL;
    
    if(head == NULL){ //若是第一个job，则设置为头指针
        head = job;
    }else{ //否则，根据pid将新的job插入到链表的合适位置
		now = head;
		while(now != NULL && now->pid < pid){
			last = now;
			now = now->next;
		}
        last->next = job;
        job->next = now;
    }
    
    return job;
}

/*移除一个作业*/
void rmJob(int sig, siginfo_t *sip, void* noused){
    pid_t pid;
    Job *now = NULL, *last = NULL;
    
    if(ingnore == 1){
        ingnore = 0;
        return;
    }
    
    pid = sip->si_pid;

    now = head;
	while(now != NULL && now->pid < pid){
		last = now;
		now = now->next;
	}
    
    if(now == NULL){ //作业不存在，则不进行处理直接返回
        return;
    }
    
	//开始移除该作业
    if(now == head){
        head = now->next;
    }else{
        last->next = now->next;
    }
    
    free(now);
}

/*组合键命令ctrl+z*/
void ctrl_Z(){
    Job *now = NULL;
    
    if(fgPid == 0){ //前台没有作业则直接返回
        return;
    }
    
    //SIGCHLD信号产生自ctrl+z
    ingnore = 1;
    
	now = head;
	while(now != NULL && now->pid != fgPid)
		now = now->next;
    
    if(now == NULL){ //未找到前台作业，则根据fgPid添加前台作业
        now = addJob(fgPid);
    }
    
	//修改前台作业的状态及相应的命令格式，并打印提示信息
    strcpy(now->state, STOPPED); 
    now->cmd[strlen(now->cmd)] = '&';
    now->cmd[strlen(now->cmd) + 1] = '\0';
    printf("[%d]\t%s\t\t%s\n", now->pid, now->state, now->cmd);
    
	//发送SIGSTOP信号给正在前台运作的工作，将其停止
    kill(fgPid, SIGSTOP);
    fgPid = 0;
}

/*fg命令*/
void fg_exec(int pid){    
    Job *now = NULL; 
	int i;
    
    //SIGCHLD信号产生自此函数
    ingnore = 1;
    
	//根据pid查找作业
    now = head;
	while(now != NULL && now->pid != pid)
		now = now->next;
    
    if(now == NULL){ //未找到作业
        printf("pid为7%d 的作业不存在！\n", pid);
        return;
    }

    //记录前台作业的pid，修改对应作业状态
    fgPid = now->pid;
    strcpy(now->state, RUNNING);
    
    signal(SIGTSTP, ctrl_Z); //设置signal信号，为下一次按下组合键Ctrl+Z做准备
    i = strlen(now->cmd) - 1;
    while(i >= 0 && now->cmd[i] != '&')
		i--;
    now->cmd[i] = '\0';
    
    printf("%s\n", now->cmd);
    kill(now->pid, SIGCONT); //向对象作业发送SIGCONT信号，使其运行
    waitpid(fgPid, NULL, 0); //父进程等待前台进程的运行
}

/*bg命令*/
void bg_exec(int pid){
    Job *now = NULL;
    
    //SIGCHLD信号产生自此函数
    ingnore = 1;
    
	//根据pid查找作业
	now = head;
    while(now != NULL && now->pid != pid)
		now = now->next;
    
    if(now == NULL){ //未找到作业
        printf("pid为7%d 的作业不存在！\n", pid);
        return;
    }
    
    strcpy(now->state, RUNNING); //修改对象作业的状态
    printf("[%d]\t%s\t\t%s\n", now->pid, now->state, now->cmd);
    
    kill(now->pid, SIGCONT); //向对象作业发送SIGCONT信号，使其运行
}

/*******************************************************
                    命令历史记录
********************************************************/
void addHistory(char *cmd){
    if(history.end == -1){ //第一次使用history命令
        history.end = 0;
        strcpy(history.cmds[history.end], cmd);
        return;
	}
    
    history.end = (history.end + 1)%HISTORY_LEN; //end前移一位
    strcpy(history.cmds[history.end], cmd); //将命令拷贝到end指向的数组中
    
    if(history.end == history.start){ //end和start指向同一位置
        history.start = (history.start + 1)%HISTORY_LEN; //start前移一位
    }
}

/*******************************************************
                     初始化环境
********************************************************/
/*通过路径文件获取环境路径*/
void getEnvPath(int len, char *buf){
    int i, j, last = 0, pathIndex = 0, temp;
    char path[40];
    
    for(i = 0, j = 0; i < len; i++){
        if(buf[i] == ':'){ //将以冒号(:)分隔的查找路径分别设置到envPath[]中
            if(path[j-1] != '/'){
                path[j++] = '/';
            }
            path[j] = '\0';
            j = 0;
            
            temp = strlen(path);
            envPath[pathIndex] = (char*)malloc(sizeof(char) * (temp + 1));
            strcpy(envPath[pathIndex], path);
            
            pathIndex++;
        }else{
            path[j++] = buf[i];
        }
    }
    
    envPath[pathIndex] = NULL;
}

/*初始化操作*/
void init(){
    int fd, n, len;
    char c, buf[80];

	//打开查找路径文件ysh.conf
    if((fd = open("ysh.conf", O_RDONLY, 660)) == -1){
        perror("init environment failed\n");
        exit(1);
    }
    
	//初始化history链表