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LScshell.c
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LScshell.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <fcntl.h>
#include <errno.h>
#include <time.h>
int main()
{
const char *exitstr="exit";
const char *cdstr="cd";
const char *pipestr="|";
const char *oredirstr=">";
const char *oaredirstr=">>";
const char *iredirstr="<";
const char *backgroundstr="&";
char cwd[512]="";//current working dir
char hname[512]="hostname";//default hostname
char user[512]="user";//default user
char cmd[512];//raw input
pid_t bpid[20]= {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; //background pid
pid_t rrpid[20]= {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; //round robin
// int at[20];//arrival time
char **cmdargv=NULL;//mykos kathe entolis i orismatos 63 megisto(paradoxi)
char *cmdbuf;//voithitiko
int n=0,i=0,loc=0,p=0,j=0;
int ctime[20]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},bstatus[20]= {-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1},temp=0,i2=0;
int flag=-1;
char *specialchar="";
void prochandler()
{
if(bpid[p-1]!=0 && flag==0) //to p exei auksithei gia na dwthei i epomeni timi ston pinaka bpid(background pid)
{
if(rrpid[j]==0)
{
rrpid[j]=bpid[p-1];//prosthiki diergasias sto telos ths ouras
}
if(rrpid[0]!=0)
{
if(ctime[j]==0)
{
ctime[j]=time(0);
kill(rrpid[0],SIGCONT);
waitpid(rrpid[0],&bstatus[j],0);
}
if((time(0)-ctime[j])>2 && !WIFEXITED(bstatus[j]) ) //time quantum gia round robin 2sec
{
puts("process late");
temp=rrpid[j];
rrpid[j]=rrpid[0];
rrpid[j-1]=temp;
for(i2=0; i2<(j-1); i++)
{
rrpid[i]=rrpid[i+1];
}
j=p;
}
else if(WIFEXITED(bstatus[j])&& j!=0)
{
printf("PID %d complete\n",rrpid[0]);
for(i2=0; i2<(j-1); i2++)
{
rrpid[i]=rrpid[i+1];
}
j=p-1;
flag=0;
}
else if(j==0 && rrpid[0]!=0 && WIFEXITED(bstatus[j])) //mono mia diergasia
{
printf("PID %d completee\n",rrpid[0]);
rrpid[0]=0;
ctime[0]=0;
j=0;
flag=-1;
}
}
}
alarm(1);
}
signal(SIGALRM,prochandler);
alarm(1);
//get local variables
if(gethostname(hname,sizeof(hname)) != 0)
{
puts("Error: cannot get computer's hostname");
}
if(getlogin_r(user,sizeof(user)) != 0)
{
puts("Error: cannot get current user's name");
};
//mainloop
while(1)
{
n=0;
specialchar=" ";
//get current working directory
if(getcwd(cwd, sizeof(cwd)) == NULL)
{
puts("Error: cannot get current working directory");
}
//print shell line info
printf("%s@%s:%s$ ",user,hname,cwd);
fgets(cmd, 512, stdin);
//get first word
cmdbuf = strtok(cmd," \n");
//pinakas me ta arguments (xwrismenes lekseis me space)
while(cmdbuf)
{
cmdargv = realloc (cmdargv, sizeof (char*) * ++n);
if (cmdargv == NULL)
{
puts("Error: memory allocation failed\n");
exit (-1);
}
cmdargv[n-1] = cmdbuf;
cmdbuf = strtok (NULL," \n");
}
//null sto telos gia execvp
cmdargv = realloc (cmdargv, sizeof (char*) * (n+1));
cmdargv[n] = 0;
if(cmdargv != NULL && *cmdargv)
{
//eswteriki entoli exit
if(strcmp(cmdargv[0],exitstr) == 0 )
{
exit(0);
}
//eswteriki entoli cd
else if(strcmp(cmdargv[0],cdstr) == 0)
{
if(chdir(cmdargv[1]) != 0)
{
puts("Error: there's no such directory");
}
}
//ekswterikes entoles
else
{
//anazhthsh gia eidikous xaraktires
for (i = 0; i < n; i++)
{
if(strcmp(cmdargv[i],pipestr) == 0)
{
specialchar="|";
loc=i;
break;
}
else if(strcmp(cmdargv[i],oredirstr) == 0)
{
specialchar=">";
loc=i;
break;
}
else if(strcmp(cmdargv[i],oaredirstr) == 0)
{
specialchar=">>";
loc=i;
break;
}
else if(strcmp(cmdargv[i],iredirstr) == 0)
{
specialchar="<";
loc=i;
break;
}
else if(strcmp(cmdargv[i],backgroundstr) == 0)
{
specialchar="&";
loc=i;
break;
}
}
//"apokodikopoihsh" eidikwn xaraktirwn
if(strcmp(specialchar,pipestr)==0)
{
int pipefd[2];
int status;
pid_t pid[2];
char **cmd1;
cmd1=malloc(sizeof(char*) * (loc+1));
char **cmd2;
cmd2=malloc(sizeof(char*) * (n-loc));
for(i=0; i<=loc; i++)
{
cmd1[i]=malloc(strlen(cmdargv[i]) * sizeof(char));
cmd1[i]=cmdargv[i];
}
for(i=0; i<(n-loc-1); i++)
{
cmd2[i]=malloc(strlen(cmdargv[loc+i+1]) * sizeof(char));
cmd2[i]=cmdargv[loc+i+1];
}
cmd2[n-loc-1]=0;
cmd1[loc] = 0;
pipe(pipefd);
pid[0]=fork();
if(!pid[0])
{
close(pipefd[0]);
dup2(pipefd[1],1);
close(pipefd[1]);
execvp(cmd1[0],cmd1);
perror(cmd1[0]);
_exit(1);
}
if(pid[0])
{
pid[1]=fork();
if(!pid[1])
{
close(pipefd[1]);
dup2(pipefd[0],0);
close(pipefd[0]);
execvp(cmd2[0],cmd2);
perror(cmd2[0]);
_exit(1);
}
}
close(pipefd[0]);
close(pipefd[1]);
waitpid(pid[1],&status,0);
}
else if(strcmp(specialchar,oredirstr)==0)
{
int out;
int status;
pid_t pid;
char **cmd1;
cmd1=malloc(sizeof(char*) * (loc+1));
char *outfile;
outfile=malloc(strlen(cmdargv[loc+1]) * sizeof(char));
outfile=cmdargv[loc+1];
for(i=0; i<=loc; i++)
{
cmd1[i]=malloc(strlen(cmdargv[i]) * sizeof(char));
cmd1[i]=cmdargv[i];
}
cmd1[loc]=0;
pid=fork();
if(pid==0)
{
out=creat(outfile, 0644);
dup2(out,STDOUT_FILENO);
close(out);
execvp(cmd1[0],cmd1);
perror(cmd1[0]);
_exit(1);
}
else
{
while (wait(&status) != pid);
}
}
else if(strcmp(specialchar,oaredirstr)==0)
{
int out;
int status;
pid_t pid;
char **cmd1;
cmd1=malloc(sizeof(char*) * (loc+1));
char *outfile;
outfile=malloc(strlen(cmdargv[loc+1]) * sizeof(char));
outfile=cmdargv[loc+1];
for(i=0; i<=loc; i++)
{
cmd1[i]=malloc(strlen(cmdargv[i]) * sizeof(char));
cmd1[i]=cmdargv[i];
}
cmd1[loc]=0;
pid=fork();
if(pid==0)
{
out=open(outfile,O_RDWR|O_CREAT|O_APPEND, 0644);
dup2(out,STDOUT_FILENO);
close(out);
execvp(cmd1[0],cmd1);
perror(cmd1[0]);
_exit(1);
}
else
{
while (wait(&status) != pid);
}
}
else if(strcmp(specialchar,iredirstr)==0)
{
int in;
int status;
pid_t pid;
char **cmd1;
cmd1=malloc(sizeof(char*) * (loc+1));
char *infile;
infile=malloc(strlen(cmdargv[loc+1]) * sizeof(char));
infile=cmdargv[loc+1];
for(i=0; i<=loc; i++)
{
cmd1[i]=malloc(strlen(cmdargv[i]) * sizeof(char));
cmd1[i]=cmdargv[i];
}
cmd1[loc]=0;
pid=fork();
if(pid==0)
{
in=open(infile,O_RDONLY,0);
dup2(in,STDIN_FILENO);
close(in);
execvp(cmd1[0],cmd1);
perror(cmd1[0]);
_exit(1);
}
else
{
while (wait(&status) != pid);
}
}
else if(strcmp(specialchar,backgroundstr)==0)
{
pid_t pid;
char **cmd1;
cmd1=malloc(sizeof(char*) * (loc+1));
for(i=0; i<=loc; i++)
{
cmd1[i]=malloc(strlen(cmdargv[i]) * sizeof(char));
cmd1[i]=cmdargv[i];
}
cmd1[loc]=0;
pid=fork();
if(pid==0)
{
execvp(cmd1[0],cmd1);
perror(cmd1[0]);
_exit(1);
}
else if(pid>0)
{
kill(pid,SIGSTOP);
bpid[p]=pid;
flag=0;
p++;
}
}
else
{
pid_t pid;
int status;
pid=fork();
if(pid==0)
{
execvp(cmdargv[0],cmdargv);
perror(cmdargv[0]);
_exit(1);
}
else
{
while (wait(&status) != pid);
}
}
}
}
}
free(cmdargv);
return 0;
}