#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<sys/wait.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<ctype.h>
int flag;
int mark;
void do_parse(char *buf,char* argv[]) {
if(buf==NULL)
{
return;
}
if(argv==NULL)
{
return;
}
int i;
int argc=0;
int status=0;
for(i=0;buf[i];i++)
{
if(!isspace(buf[i]) &&status==0 )
{
argv[argc++]=buf+i;
status=1;
}else if( isspace(buf[i]))
{
status=0;
buf[i]='\0';
}
}
argv[argc]=NULL;
}
int has_pipe(char* argv[])
{
int i=1;
//Start form 1 because before '|' should have command.
while(argv[i]!=NULL)
{
if(strcmp(argv[i],"|")==0)
{
argv[i]=NULL;
return i+1;
}
if(strcmp(argv[i],">") == 0)
{
argv[i] = NULL;
flag =1;
return i+1;
}
if(strcmp(argv[i],"<") == 0)
{
argv[i] = NULL;
mark = 1;
return i+1;
}
i++;
return 0;
}
}
int main()
{
char* argv[16];
char buf[1024]={0};
char* tmp1[8];
char* tmp2[8];
int fd[2];
int ret;
int fd1;
do
{
flag = 0;
mark = 0;
printf("[myshell~]");
fflush(stdout);
// read(1,buf,1024);
scanf("%[^\n]%*c",buf);
do_parse(buf,argv);
ret=has_pipe(argv);
// 管道实现
// 要想实现管道，必须调用两个exec函数，所以要有子进程和孙子进程
// 把命令分出来，让子进程调用pipe函数
if(ret && !flag && !mark)
{
int i=0;
int j=ret;
while(argv[i]!=NULL)
{
tmp1[i]=argv[i];
i++;
}
tmp1[i]=NULL;
i=0;
while(argv[j]!=NULL)
{
tmp2[i++]=argv[j++];
}
tmp2[i]=NULL;
pid_t pid_p=fork();
if(pid_p==-1)
{
perror("pid_p");
exit(EXIT_FAILURE);
}
else if(pid_p==0)
{
if(pipe(fd)==-1)
{
perror("pipe");
exit(EXIT_FAILURE);
}
pid_t pid_s=fork();
if(pid_s==-1)
{
perror("pid_s");
exit(EXIT_FAILURE);
}
else if(pid_s==0)
{
close(fd[0]);
dup2(fd[1],1);
execvp(tmp1[0],tmp1);
}
else
{
close(fd[1]);
dup2(fd[0],0);
execvp(tmp2[0],tmp2);
}
}
else{
wait(NULL);
}
}
else {
pid_t pid=fork();
if(pid==-1)
{
perror("pid");
exit(EXIT_FAILURE);
}
else if(pid==0)
{
//输出重定向
if(flag)
{
fd1 = open(argv[ret],O_WRONLY|O_CREAT,0664);
close(1);
dup2(fd1,1);
}
//输入重定向
if(mark)
{
// close(0);
fd1 =open(argv[ret],O_RDWR|O_CREAT,0644);
//close(0);
dup2(fd1,0);
}
int a = execvp(argv[0],argv);
if(a == -1)
{
perror("ececvp");
}
if(flag||mark)
{
close(fd1);
}
}else{
wait(NULL);
}
}
memset(buf,0,1024);
}while(buf[0] != 'q');
}