Linux C编程实战——第七章 进程控制_项目实现_自写shell

自写shell

基本介绍：该shell命令目前实现了cd命令，tab补全，history历史,和外部命令。

基本实现原理 : 根据输入命令，解析参数，然后再fork一个进程，在进程中利用execvp运行外部命令，其cd命令根据chdir()函数实现，tab补全和历史利用readdir()函数及库实现。

这是大概思想，下面直接上代码(已经加上详细注释)：

注意：在运行该程序前要安装readline对应的库，安装流程如下：

http://blog.csdn.net/chudongfang2015/article/details/52068026

myshell.c:

/*************************************************************************> File Name: meshell.c> Author:chudongfang > Mail:[e-mail] > Created Time: 2016年07月28日 星期四 09时31分43秒 ************************************************************************/#include <pwd.h>#include <fcntl.h>#include <dirent.h>#include <sys/types.h>#include <unistd.h>#include <sys/stat.h>#include <sys/resource.h>#include <sys/wait.h>#include <stdio.h>#include <string.h>#include <math.h>#include <readline/readline.h>#include <readline/history.h>#include <stdlib.h>#define  MAX_SIZE 256#define normal          0  //正常命令#define out_redirect    1  //重定向输出#define in_redirect     2  //重定向输入#define have_pipe       3  //管道命令void do_cmd(int argcout,char arglist[100][256],int his_count,char history[][256]);int find_command(char *command);           void explain_input(char *buf,int *argcout,char arglist[100][256]);void get_input(char *buf,char *path,int *his_count,char history[][256]);struct passwd *pw;  //用户信息结构体int main(int argc,char *argv[]){int i;        char history[256][256];//存储历史    int his_count=0;       //历史的数量    int argcout = 0;        //命令计数器char arglist[100][256]; //储存命令char **arg = NULL;      char *buf  = NULL;      //临时字符数组char path [MAX_SIZE];   //进程所在路径    memset(history,0,sizeof(history));buf = (char *)malloc(256);   if(buf == NULL){perror("malloc failed");exit(-1);}while(1){memset(buf,0,256);             memset(path,0,MAX_SIZE);  if (getcwd( path, MAX_SIZE) == NULL)    //得到当前路径{    printf("read path error!\n");    exit(-1);}//获取当前目录绝对路径，即去掉程序名get_input(buf,path,&his_count,history);                 //输出路径提示，并得到输入命令   while(strlen(buf) == 0)                  {  get_input(buf,path,&his_count,history);                //无输入，继续接受输入}if( strcmp(buf,"exit\n") == 0 || strcmp(buf,"logout\n") == 0)  //exit 和 logout 退出shellbreak;for(i=0;i<100;i++)                   //初始化命令         {arglist[i][0]='\0';           }argcout = 0;                         //命令个数为0explain_input(buf,&argcout,arglist); //把输入解析成命令 do_cmd(argcout,arglist,his_count,history);             //对命令进行分析，操作}if(buf != NULL){free(buf);buf = NULL;}    exit(0);}/**************************************** * 函数功能： 实现提示，接受输入，tab 补全，记录输入历史 *  * 函数参数：  *  参数1 ：输入 *  参数2 ：解析后的命令 ***************************************************/void get_input(char *buf,char *path,int *his_count,char history[][256]){    int count=0,i,len;uid_t  uid;    char  *temp;  char  str[500];    uid = getuid ();  //得到uid       pw = getpwuid (uid);    //得到用户信息    if (!pw)      {          printf ("Couldn't find out about user %d./n", (int)uid);          return ;      }  sprintf(str,"\033[;31m %s@\033[0m\033[;31mmyshell\033[0m\033[;32m %s\033[0m\033[;33m$\033[0m",pw -> pw_name,path);    //加上颜色，合成提示语句str    temp = (char* )malloc(sizeof(256));  //malloc 申请空间，用于readline 注意： readline 返回值只能用malloc申请的指针接受    memset(temp,0,sizeof(temp));  //初始化空间    temp = readline(str);         //调用readline库函数 实现补全   ,调用方法在另一篇博客    strcpy(buf, temp);            //把接受到的存入到buf里面    //历史记录，如果输入的全部是空格或是换行，则不存储     len = strlen(buf);               for(i=0;i < len; i++)        if(buf[i] == ' '||buf[i] == '\n')             count++;        if(count != len)    {        //如果输入的命令与前一个重复，则不把其记录到history里面        if(*his_count != 0){            if(strcmp(history[*his_count-1],buf) != 0){                strcpy(history[*his_count],buf);                *his_count = *his_count + 1;                add_history(buf);            }        }        else        {            strcpy(history[*his_count],buf);            *his_count = *his_count + 1;            add_history(buf);        }    }        free(temp);}/************************************************* * 函数功能 ：根据输入的内容解析出命令 * 函数参数： *  1 ：输入的内容 *  2 ：命令个数 *  3 ：存储命令数组 *************************************************/void explain_input(char *buf,int *argcout,char arglist[100][256]){int number = 0 ;char *p = buf;char *q = buf;while(1){if(p[0] == '\n' || p[0] == '\0')break;if(p[0] == ' ')p++;else{q=p;number = 0;while( (q[0] != ' ') && q[0] != '\0' &&q[0] != '\n'){number++;//代表单个命令的长度q++;}strncpy(arglist[*argcout],p,number+1);   //把单个命令解析出来arglist[*argcout][number] = '\0';         //最后加上结尾*argcout = *argcout + 1; p=q;}}}/***************************************************** * 函数功能 ：命令分类，并执行命令 * 参数： *  1：命令个数 *  2：存储命令数组 * **************************************************/void do_cmd(int argcout,char arglist[100][256],int his_count,char history[][256]){int flag=0;int how =0;int backgroud = 0;int status;int i;int fd;char * arg[argcout + 4];char * argnext[argcout + 4];char *file;char home[256];pid_t pid;for(i=0;i<argcout;i++)arg[i]=(char *)arglist[i];    arg[argcout] = NULL;    //解析是否是后台运行for(i=0;i < argcout;i++){if(strncmp(arg[i],"&",1) == 0){if(i == argcout - 1){backgroud = 1;arg[argcout - 1] =NULL;break;}else {printf("wrong command\n");return ;}}}for(i=0 ;arg[i] != NULL; i++){//解析重定向输入        if(strcmp(arg[i],">") == 0){flag++;how = out_redirect;if (arg[i+1] == NULL)flag++;}        //解析重定向输出if( strcmp(arg[i],"<") == 0){flag++;how = in_redirect;if(i == 0)flag++;}        //解析管道命令if( strcmp(arg[i],"|") == 0){flag++;how = have_pipe;if(arg[i+1] == NULL)flag++;if( i == 0)flag++;}}if(flag > 1){printf("wrong command !\n");return ;}/**************解析重定向输出文件名*******************/if( how == out_redirect){for(i=0;arg[i]!=NULL;i++){if(strcmp(arg[i],">") == 0){file = arg[i+1];arg[i] = NULL;}}}/*******************解析重定向输入文件名**********************/if(how == in_redirect){for(i=0; arg[i] != NULL;i++){if(strcmp(arg[i],"<") == 0){file = arg[i+1];arg[i] = NULL;}}}/***************解析管道命令参数*******************/if(how == have_pipe){for( i=0; arg[i]!=NULL ;i++){if(strcmp(arg[i],"|") == 0){arg[i] = NULL;int j;for(j=i+1;arg[j]!=NULL;j++){argnext[j-i-1] = arg[j];}argnext[j-i-1] = arg[j];break;}}}  // 如果命令为history 则输出历史。    if(strcmp(arg[0],"history") == 0&& argcout == 1){        printf("tolal num %d :\n",his_count);        for(i=0;i<his_count;i++){            printf("%d\t%s\n",i+1,history[i]);        }        goto loop;    }/*********************CD命令****************************///cd命令为内嵌命令，，因为chdir只能改变其本身进行的目录      if(strcmp(arg[0],"cd") == 0){sprintf(home,"/home/%s/",pw->pw_name);        if(argcout == 1 || argcout == 2 && strcmp(arg[1],"~") == 0) //特殊情况判断{    chdir(home);            goto loop;}        if(chdir(arg[1]) == -1){            perror("chdir");        }        goto  loop;}//fork一个子进程，执行参数if( (pid = fork()) < 0){printf("fork error\n");return ;}switch(how){/***************************普通命令*************************/case 0:        //子进程if(pid == 0){if( !(find_command(arg[0])) ){printf("%s :command not found !\n",arg[0]);exit(0);}execvp(arg[0],arg);exit(0);}break;/************************重定向输入命令**************************/case 1:if(pid == 0){if( !(find_command(arg[0])) ){printf("%s :command not found !\n",arg[0]);exit(0);}            //打开一个文件fd = open(file,O_RDWR | O_CREAT | O_TRUNC,0644);//把屏幕输出流给文件            dup2(fd,1);execvp(arg[0],arg);//加载参数命令exit(0);}break;/**********************重定向输出命令**************************/        case 2:if(pid == 0){if( !(find_command(arg[0])) ){printf("%s :command not found !\n",arg[0]);exit(0);}            //打开文件fd = open(file,O_RDONLY);//把键盘输入流给文件            dup2(fd,0);execvp(arg[0],arg);            close(fd);exit(0);}break;/**********************管道命令*************************/case 3:if(pid == 0){int pid2;int status2;int fd2;            //fork一个子进程，运行管道符前命令if( (pid2 = fork()) < 0){printf("fork2 error\n");return ;}else if(pid2 == 0){if(!(find_command)(arg[0])){printf("%s :command not found !\n",arg[0]);exit(0);}                                                //打开文件，将屏幕输出流1 给 fd2，其向屏幕输出的数据就存储到文件当中                if((fd2 = open("/tmp/tempfile",O_WRONLY | O_CREAT | O_TRUNC ,0644)) == -1)                    printf("open /tmp/tempfile failed!");dup2(fd2,1);                execvp(arg[0],arg);                close(fd2);                exit(0);}            //等待管道符前面命令执行完            if(waitpid(pid2,&status2,0) == -1){printf("wait for child process error\n");}            //管道后命令开始执行            if(!(find_command)(argnext[0])){printf("%s :command not found !\n",argnext[0]);exit(0);}                       if((fd2 = open("/tmp/tempfile",O_RDONLY)) == -1) {                perror("Open");            }dup2(fd2,0);execvp(argnext[0],argnext);if(remove("/tmp/tempfile") == -1)//移除文件perror("remove");exit(0);}break;default :break;}/**********************杀死父进程，后端运行********************************/        if(backgroud ==1  && pid != 0){        printf("[process id %d]\n",pid);        exit(0);    }/************************父进程等待子进程退出******************************/        if(waitpid(pid,&status,0) == -1){        printf("wait for child process error!\n");    }loop: ;}int find_command(char *command){DIR *dp;struct dirent*  dirp;char *path[]={"./","/bin","/usr/bin",NULL};//在一下路径下，找可执行程序if(strncmp(command,"./",2) == 0)command =command + 2;int i=0;while(path[i]!=NULL){if((dp = opendir(path[i])) == NULL){//打开目录printf("can not open /bin\n");}while((dirp = readdir(dp)) != NULL){       //比较是否有相同的文件if(strcmp(dirp -> d_name,command) == 0){closedir(dp);return 1;}}closedir(dp);   i++;}return 0;}

Makefile:

cc = gccOBJ = myshellall :$(cc)  -c  ./*.c$(cc)  -o $(OBJ)  ./*.o  -I /usr/lib/x86_64-linux-gnu/libreadline.so  -lreadline -ltermcap  -grm -rf  *.oclean:rm -rf *.o