【Linux】简易shell外壳的制作

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>#define NUM 1024
#define SIZE 32
#define SEP " "// 保存完整的命令行字符串
char cmd_line[NUM];
// 保存打散之后的命令行字符串
char *g_argv[SIZE];// shell 运行原理：通过让子进程执行命令，父进程等待&&解析命令
int main()
{// 0. 命令行解释器，一定是一个常驻内存的进程，不退出while(1){// 1. 打印提示信息 [zs@localhost myshell]#printf("[zs@localhost myshell]# ");fflush(stdout);// 2. 获取输入信息[输入的是各种指令和选项]memset(cmd_line, '\0', sizeof cmd_line);if(fgets(cmd_line, sizeof cmd_line, stdin) == NULL){continue;}// "ls -l -a\n\0"cmd_line[strlen(cmd_line) - 1] = '\0';//printf("echo: %s\n", cmd_line);// 3. 命令行字符串解析："ls -l -a" -> "ls" "-l" "-a"g_argv[0] = strtok(cmd_line, SEP); // 第一次调用，要传入原始字符串int index = 1;if(strcmp(g_argv[0], "ls") == 0){g_argv[index++] = (char*)"--color=auto";}if(strcmp(g_argv[0], "ll") == 0){g_argv[0] = (char*)"ls";g_argv[index++] = (char*)"-l";g_argv[index++] = (char*)"--color=auto";}while(g_argv[index++] = strtok(NULL, SEP)); // 之后继续解析原始字符串，传入NULL// for debug//for(index = 0; g_argv[index]; ++index)//{//    printf("g_argv[%d]: %s", index, g_argv[index]);//}// 4. 让父进程(shell)自己执行的命令，叫做内置命令/内建命令 if(strcmp(g_argv[0], "cd") == 0){if(g_argv[1] != NULL){   chdir(g_argv[1]);}}// 5. fork()pid_t id = fork();if(id == 0){// 子进程execvp(g_argv[0], g_argv);exit(1);}// fatherint status = 0;pid_t ret = waitpid(id, &status, 0);if(ret > 0){printf("exit code: %d\n", WEXITSTATUS(status));}}
}