最好的淘宝网站建设,python可以用来干什么,网站建设与维护高职,北京公司注册中介正规文章目录 minishell支持重定向minishell完整代码 minishell支持重定向
支持重定向的核心逻辑#xff1a; 1.分析字符串是否含有重定向的符号#xff0c;并且提取文件名。
#define INPUT_REDIR 0 //输入重定向
#define OUTPUT_REDIR 1 //输出重定向
#define APPEND_REDIR… 文章目录 minishell支持重定向minishell完整代码 minishell支持重定向
支持重定向的核心逻辑 1.分析字符串是否含有重定向的符号并且提取文件名。
#define INPUT_REDIR 0 //输入重定向
#define OUTPUT_REDIR 1 //输出重定向
#define APPEND_REDIR 2 //追加重定向
#define NONE_REDIR 4 //没有重定向
int redir_status NONE_REDIR;//状态char* CheckRedir(char* start)
{ assert(start); char* end start strlen(start)-1; //end执行指令的最后一个内容 while(start end) { if(*end ) { if(*(end -1) ) { //ls -a -llog.txt\0 追加redir_status APPEND_REDIR; *(end-1) \0; end; break; } //ls -a -llog.txt\0 输出redir_status OUTPUT_REDIR; *(end) \0; end; break;}else if(*end ){//ls -a -llog.txt\0 输入redir_status INPUT_REDIR;*end \0;end;break;}else {end--;}}//循环结束如果end还是大于start说明存在重定向if(end start){return end;}//走到这说明不存在重定向return NULL;
}例子 end开始向前找重定向符 然后end 这样end指向的就是文件名start执行的就是指令内容。 然后就开始在子进程进行重定向了。
//printf(parent process create subprocess success\n); if(sep) { int fd -1; switch(redir_status) { case INPUT_REDIR: fd open(sep,O_RDONLY); dup2(fd,0); break; case OUTPUT_REDIR: fd open(sep,O_WRONLY | O_CREAT | O_TRUNC,0666); dup2(fd,1); break; case APPEND_REDIR: fd open(sep,O_WRONLY | O_CREAT | O_APPEND,0666); dup2(fd,1); break; default: assert(NULL); break; } }minishell完整代码
#include stdio.h
#include string.h
#include unistd.h
#include sys/types.h
#include sys/stat.h
#include fcntl.h
#include sys/wait.h
#include stdlib.h
#include assert.h#define NUM 1024
#define SIZE 32
#define SEP #define INPUT_REDIR 0
#define OUTPUT_REDIR 1
#define APPEND_REDIR 2
#define NONE_REDIR 4
int redir_status NONE_REDIR;char cmd_line[NUM];//array for saving command line
char* g_argv[SIZE];//the array are used to store paresed commands
char g_myval[64];char* CheckRedir(char* start)
{assert(start);char* end start strlen(start)-1;while(start end) {if(*end ){if(*(end -1) ){//ls -a -llog.txt\0redir_status APPEND_REDIR;*(end-1) \0;end;break;}//ls -a -llog.txt\0 redir_status OUTPUT_REDIR;*(end) \0;end;break;}else if(*end ){//ls -a -llog.txt\0redir_status INPUT_REDIR;*end \0;end;break;}else {end--;}}if(end start){return end;}return NULL;
}
int main()
{//1.命令行解释器一定是一个常驻内存的进程不退出while(1) {//2.显示提示行printf([xiaolinlocalhost myshell]#);fflush(stdout);memset(cmd_line,\0,sizeof cmd_line);//3.获取用户输入的字符串if(fgets(cmd_line,sizeof cmd_line,stdin) NULL){//if cmd_line empty contiue get commandcontinue;}cmd_line[strlen(cmd_line)-1] \0;char* sep CheckRedir(cmd_line);//4.对字符串进行解析int index 0;g_argv[index] strtok(cmd_line,SEP);//Firest parse cmd_line while(1)//Second parse cmd_line dont pass cmdline;{g_argv[index] strtok(NULL,SEP);if(g_argv[index] NULL) break;index;}if(strcmp(g_argv[0],ls) 0){g_argv[index] (char*)--colorauto;g_argv[index] NULL;} if(strcmp(g_argv[0],ll) 0){ g_argv[0] (char*)ls;g_argv[1] (char*)-l;g_argv[2] (char*)--colorauto;g_argv[3] NULL;}// processing of built-in commandsif(strcmp(g_argv[0],cd) 0){//chdir() changes the current working directory of the calling process to the directory specified in path.if(g_argv[1] ! NULL) chdir(g_argv[1]);continue;}if(strcmp(g_argv[0],export) 0 g_argv[1] ! NULL){//There is a very hidden issue here//Ptuenv passes an environment variable as a pointer to it //And g_ Argv [1] will be cleared on the next command_line read//In this way, the environment variable pointer points to a place with empty data, and this pointer is also a null pointer//int res putenv(g_argv[1]);//if(res 0) printf(export success\n);//else printf(export fail\n);//solve the problemstrcpy(g_myval,g_argv[1]);int res putenv(g_myval);if(res 0) printf(export success\n);else printf(expor fail\n);continue;}/*//test if the g_argv array id correct for(index 0; g_argv[index]; index){printf(g_argv[%d]:%s\n,index,g_argv[index]);}*///5.create subprocess execute commandpid_t id fork();if(id 0){//subprocess//printf(parent process create subprocess success\n);if(sep){int fd -1;switch(redir_status){case INPUT_REDIR:fd open(sep,O_RDONLY);dup2(fd,0);break;case OUTPUT_REDIR:fd open(sep,O_WRONLY | O_CREAT | O_TRUNC,0666);dup2(fd,1);break;case APPEND_REDIR:fd open(sep,O_WRONLY | O_CREAT | O_APPEND,0666);dup2(fd,1);break;default:assert(NULL); break;}}printf(subprocess starts running\n);execvp(g_argv[0],g_argv);printf(subprocess replace fail\n);}else if(id 0){//parent processint status 0;pid_t res waitpid(-1,status,0);//blocking waitingif(res -1){printf(parent process wait subprocess fail\n);}else if(res 0){printf(parent process wait subprocess success exit_code:%d\n,WEXITSTATUS(status));}else {printf(unkown error\n);}}else{//failprintf(parent procrss create subprocess fail\n);}}return 0;
}
