1 #include <stdio.h>
2 #include <unistd.h>
3 #include <stdlib.h>
4 #include <string.h>
5 #include <fcntl.h>
6 #include <sys/types.h>
7 #include <sys/stat.h>
8 int main(){
9 //1.等待用户输入
10 while(1){
11 printf("[fw@localhost$ root] ");
12 char str[1024] = {0};//设置最大的长度
13 if(scanf("%[^\n]%*c",str)!=1){
14 getchar();
15 continue;
16 }
17 //选出>或者>>两种符号
18 int fd = 1;
19 int dup_flag = 0;
20 char* dup_file;
21 char* ff = str;
22 while(*ff!='\0'){
23 if(*ff == '>'){
24 dup_flag = 1;
25 *ff = '\0';
26 ff++;
27 if(*ff == '>'){
28 dup_flag = 2;
29 *ff = '\0';
30 ff++;
31 }
32 while(*ff==' '){
33 ff++;
34 }
35 dup_file = ff;
36 }
37 ff++;
38 }
39
40 //2.解析输入数据,用数组存储起来，
41 char* s[32]={0};
42 char* start = str;
43 char* end = str;
44 int i = 0;
45 while(*end !='\0'){
46 if(*end!=' '){
47 s[i++] = end;
48 while(*end!=' '&&*end!='\0'){
49 end++;
50 }
51 }
52 *end = '\0';
53 end++;
54 }
55 s[i]= NULL;
56 if(strcmp(s[0],"cd") == 0){
57 // int chdir(const char *path);
58 chdir(s[1]);
59 continue;
60 }
61 //3.创建子进程，在子进程中进行数据读
62 //4.等待子进程退出
63 pid_t pid;
64 pid = fork();
65 if(pid<0){
66 continue;
67 }
68 else if(pid == 0){//创建一个子进程执行逻辑
69 //找到文件描述符
70 if(dup_flag == 1){
71 fd = open(dup_file,O_WRONLY|O_CREAT|O_TRUNC);
72 }
73 if(dup_flag == 2){
74 fd = open(dup_file,O_WRONLY|O_CREAT|O_APPEND);
75 }
76 dup2(fd,1);
77 // int execvp(const char *file, char *const argv[]);
78 if(execvp(s[0],s)<0){
79 perror("");
80 }
81 exit(0);
82 }
83 wait(NULL);//父进程等待子进程的推出，防止产生僵尸进程
84 }
85 return 0;
86 }
