编写shell脚本，实现基本的linux命令和自定义管道功能

在shell中输入“ls || more"能够执行ls命令并将其通过管道传送给more作为标准输入。

源码

#include<stdio.h>
#include<unistd.h>
#include<wait.h>
#include<string.h>
int main(){

        printf("welcome to my shell!\n");
        char cmd[1024];
        //printf("%d\n",argc);
        while(1){
                printf("myshell> ");
                gets(cmd);
                if(strcmp(cmd, "exit")==0) break;
                else if(strcmp(cmd, "help")==0){
                        printf("-----------\ninner commands: \n");
                        printf("help: print help infomation\n");
                        printf("story: tell stories\n");
                        printf("exit: exit this\n -----------\nouter commands:\n");
                        printf("command:ps-ls--\n-----------\n");
                        printf("command-pipe: ||\n:");

                }
                else if(strcmp(cmd, "story")==0){
                        printf("no stories to tell you!\n");
                }
                else if(strstr("ls-ps",cmd)!=NULL){
                        /*char *argv[10];
                        char *p;
                        int argc = 1;
                        char delims[2]=" ";
                        strcpy(argv[0], strtok(cmd, delims));
                        while(p = strtok(NULL, delims)){
                                strcpy(argv[argc],p);
                                argc++;
                        }*/

                        //printf("argc:%d\n",argv[0]);
                        pid_t pid = fork();
                        if(pid > 0)  // parent
                        {
                                wait(NULL);
                                continue;
                        }
                        if(pid==0)  //child
                        {
                                int s = execlp(cmd, cmd, NULL);
                                if(s==-1) printf("fail to exec %s\n", cmd);
                                return 0;
                        }



                }
                else if(strstr(cmd,"||")!=NULL){
                        puts(cmd);
                        const char s[3] = "| ";
                        char *command1;
                        char *command2;
                        int fd[2], res;
                        int status;

                        command1 = strtok(cmd, s);
                        command2 = strtok(NULL, s);
                        printf("%s\n", command1);
                        printf("%s\n", command2);
                        res = pipe(fd);
                        if(res == -1){
                                printf("pipe failed!\n");
                        }

                        pid_t pid1 = fork();
                        if(pid1 == -1){
                                printf("fork failed !\n");
                        }
                        else if(pid1 == 0){
                                int num1 = dup2(fd[1], 1); // dup the stdout
                               close(fd[0]);
                                if(execlp(command1,command1, NULL)<0){
                                        printf("%s: command not found\n", command1);
                                }
                        }
                        else{
                                waitpid(pid1, &status, 0);

                                pid_t pid2 = fork();
                                if(pid2 == -1)
                                        printf("fork failed!\n");
                                else if(pid2 == 0){
                                        close(fd[1]); //close write edge
                                        dup2(fd[0], 0);
                                        if(execlp(command2,command2, NULL)<0){
                                                printf("%s:command not found\n",command2);
                                        }
                                }
                                else{
                                        close(fd[0]);
                                        close(fd[1]);
                                        waitpid(pid2, &status, 0);
                                }

                        }

                }
                else {
                        printf("invalid command!\n");
                }




        }
        return 0;
}
                                                                                                                                                               113,1         Bot

只实现了简单的功能，更加丰富的功能可以扩展。