myshell.c

操作系统课程中,命令行解释程序,可以把用户输入的命令翻译为计算机可以执行的语言.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <time.h>
#include <sys/timeb.h>

void sig_usr1(int sig);
extern char **getline();
double trans16(char*);
double pow(double,double);
int checkdigit(char*);
int checkxdigit(char*);

main() 
{
  int i;
  char **args;
	FILE *in;

  while(1) {

	printf("Myshell $:");
   args = getline();

   if(!(strcmp(args[0],"exit")))
   	exit(0);//end for if,the 0 level;
	
	else if(!(strcmp(args[0],"time")))
{
	time_t timep;
	time(&timep);
	printf("%s",asctime(gmtime(&timep)));
	printf("%s",ctime(&timep));
	clock_t s;s=clock();
	printf("%s\n",s);
	struct timeb tp;
	ftime(&tp);
	printf("time:%d\nmillitm:%d\ntimezone:%d\ndstflag:%d\n",
	tp.time,tp.millitm,tp.timezone,tp.dstflag);

}
	else if(!(strcmp(args[0],"ld"))){
    pid_t pid;

	if((pid=fork())<0){
       			printf("error fork.");
					exit(0);}
	else if(pid == 0){
	in=freopen("aaa","w",stdout);
			execvp("ls",0);

			}
			else
	{wait(NULL);}
			
}//end for else if,the 0 level;
		
	else if(!(strcmp(args[0],"la"))){
    pid_t pid;
	if((pid=fork())<0){
       			printf("error fork."); 
					exit(0);}
	else if(pid == 0){
	sigset(SIGUSR1,sig_usr1);
	sighold(SIGUSR1);
	execvp("ls",args);}
			
else
  sigignore(SIGUSR1);
			
}//end for else if,the 0 level;


		else if(!(strcmp(args[0],"ls")))
{
					char *buff[1000];
               int fd[2];
               pid_t pid;
               pid_t pid2;

               if(pipe(fd)<0)
               printf("pipe error");

              if((pid=fork())<0)
                printf("fork error");
              else if (pid==0){
                 close(fd[1]);
                 popen("ls -l |more","w");
                 read(fd[0],buff,1000);
                 printf("%s",buff);
                 close(fd[0]);
                 			 }
           		else{
               close(fd[0]);
              //freopen("text","w",stdout);
					//	execvp("ls",args);
              write(fd[1],"text",sizeof("text"));
              close(fd[1]);
        }
}//end for else if "ls",the 0 level;
		
		else if(!strcmp(args[0],"args"))
{
		i=1;int count=0,j=0;
		for(;args[i]!=NULL;i++)
		{
		if(!strcmp(args[i],"\""))
		{
		j=(j+1)%2;if(j==0)count++;
		}
		else if(j==0)count++;
		else;
		}
		printf("argc = %d , args = ",count);//display the beginning of the output.
		j=0;
		for(i=1;args[i]!=NULL;i++)
		{
		if(!strcmp(args[i],"\""))
		{
		if(j==0||args[i+1]==NULL)printf("%s",args[i]);
		else  printf("%s ,",args[i]);
		j=(j+1)%2;
		}
		else if(j==1)
		printf("%s ",args[i]);
		else 
		{
		if(args[i+1]==NULL)printf("%s ",args[i]);
		else printf("%s , ",args[i]);
		}
		}
		printf("\n");

}//end for else if "args " the 0 level;

      else if(!strcmp(args[0],"add"))
	{
		int sign=1;
		double sum=0;int j=0;
		for(i=1;args[i]!=NULL;i++)
		{
		if(strncmp(args[i],"0x",2)!=0)
		{
		if(checkdigit(args[i]))
		sum=sum + atof(args[i]);
		else
		{sign=0;break;}
		}
		else
		{
		if(checkxdigit(args[i]+2))
		sum=sum +trans16(args[i]);
		else
		{sign=0;break;}
		}
		}
		if(sign==1)
		for(j=1;j<i;j++)
		{
		printf("%s",args[j]);
		if(j==i-1)
		printf(" = %f\n",sum);
		else
		printf(" + ");
		}
		else
		printf("There exists a error at ->%s;\n",args[i]);
	}//end for else if,the 0 level;

                                              
}//end for while loop;

}//end for main function;

void sig_usr1(int sig){
        sigset(sig,sig_usr1);
        return;

}//end for sig_usrl();

int checkdigit(char *a)
{
int size=strlen(a);
int i=0;
int sign=1;
for(;i<size;i++)
{
if(!isdigit(a[i]))
{sign=0;break;}
}
return sign;
}//check for checkdigit();

int checkxdigit(char *a)
{
int size=strlen(a);
int i=0;
int sign=1;
for(;i<size;i++)
{
if(!isxdigit(a[i]))
{sign=0;break;}
}
return sign;
}//end for checkdigit();

double trans16(char*a)
{
a=a+2;
int size=strlen(a);
double sum=0;
int i=0;
for(i=0;i<size;i++)
{
int x=isdigit(a[i])?(a[i]-48)*(pow(16.0,size-i-1)):(a[i]-97+10)*(pow(16.0,size-i-1));
sum=sum+x;
}
return sum;
}//end for trans16();

double pow(double x,double y)
{
int sum=1;
int i=0;
for(i=0;i<(int)y;i++)
sum=sum*x;
return sum;
}//end for pow();