焦点要闻：代码1
#include<stdio.h>
#include<stdlib.h>
(资料图片仅供参考)
#include<sys/wait.h>
#include<string.h>
#include<unistd.h>
#include<fcntl.h>7
#define MAX_ARGS 10
#define MAX_BUFFER 1024
int main()
{
char buffer[MAX_BUFFER];
char* args1[MAX_ARGS];
char* args2[MAX_ARGS];
char* args[MAX_ARGS];
int num_args2=0;
int num_args1=0;
int num_args=0;
pid_t pid2,pid1,pid;
int fd[2];
int background_flag=0;
while(1) {
printf("myshell>");
if(fgets(buffer,MAX_BUFFER,stdin)==NULL)
break;
buffer[strlen(buffer)-1]='\0';
char* token=strtok(buffer," ");
while(token!=NULL){
if(strcmp(token,">")==0){
char* file_name=strtok(NULL," ");
int fd = open(file_name,O_WRONLY | O_CREAT | O_TRUNC,
S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
dup2(fd,STDOUT_FILENO);
close(fd);
break;
}
else if(strcmp(token,"<")==0){
char* file_name=strtok(NULL," ");
int fd=open(file_name,O_RDONLY);
dup2(fd,STDIN_FILENO);
close(fd);
break;
}
else if(strcmp(token,"|")==0){
num_args1=0;
token=strtok(NULL," ");
while(token!=NULL && strcmp(token,">")!=0 &&
strcmp(token,"<")!=0){
args1[num_args1]=token;49
num_args1++;
token = strtok(NULL," ");
}
args1[num_args1]=NULL;
if(token!=NULL){
if(strcmp(token,">")==0){
char* file_name=strtok(NULL," ");
int fd = open(file_name,O_WRONLY | O_CREAT | O_TRUNC,
S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
dup2(fd,STDOUT_FILENO);
close(fd);
}
else if(strcmp(token,"<")==0){
char* file_name=strtok(NULL," ");
int fd=open(file_name,O_RDONLY);
dup2(fd,STDIN_FILENO);
close(fd);
}
}
pipe(fd);
pid1=fork();
if(pid1==0){
close(fd[0]);
dup2(fd[1],STDOUT_FILENO);
execvp(args1[0],args1);
exit(1);
}
else if(pid>0){
close(fd[1]);
num_args2=0;
token=strtok(NULL," ");
while(token!=NULL && strcmp(token,">")!=0 &&
strcmp(token,"<")!=0){
args2[num_args2]=token;
num_args2++;
token = strtok(NULL," ");
}
args2[num_args2]=NULL;
if(token!=NULL){
if(strcmp(token,">")==0){
char* file_name=strtok(NULL," ");90
int fd = open(file_name,O_WRONLY | O_CREAT | O_TRUNC,
S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
dup2(fd,STDOUT_FILENO);
close(fd);
}
else if(strcmp(token,"<")==0){
char* file_name=strtok(NULL," ");
int fd=open(file_name,O_RDONLY);
dup2(fd,STDIN_FILENO);
close(fd);
}
}
pid2 =fork();
if(pid2==0){
dup2(fd[0],STDIN_FILENO);
execvp(args2[0],args2);
exit(1);
break;
}
else if(pid2>0){
waitpid(pid1,NULL,0);
waitpid(pid2,NULL,0);
}
else{
perror("fork");
exit(1);
break;
}
}
else {
perror("fork");
exit(1);break;
}
}
else if(strcmp(token,"&")==0){
background_flag =1;
break;
}
else{
args[num_args]=token;
num_args++;
}
token=strtok(NULL," ");
}
args[num_args]=NULL;
pid =fork();
if(pid==0){
execvp(args[0],args);
exit(1);
}
else if(pid>0){
if(background_flag){
background_flag=0;
}
else{
waitpid(pid,NULL,0);
}
}
else{
perror("fork");
exit(1);
}
num_args1=0;
num_args2 =0;
memset(args1,0,sizeof(args1));
memset(args2,0,sizeof(args2));
num_args=0;
memset(args,0,sizeof(args));
}
return 0;
}