#include<stdlib.h>

#include<stdio.h>

#include<unistd.h>

#include<sys/types.h>

#include<errno.h>

#include<string.h>

#include <sys/wait.h>

#include<fcntl.h>

#include<limits.h>

//Defining A Structure

typedef struct node

}node;

char seps[]=" \t";

node procs[10000];

int counters=0;

int flag=0;

pid_t pp;

char *source;

int array[10000];

int ctr=0;

char *in1='\0';

char *out1='\0';

//Function for executing all the basic shell commands

void execs(char *arr[],int rlflag,int rgflag)

{

int sin=dup(STDIN_FILENO);

int sout=dup(STDOUT_FILENO);

pp=fork();

if(flag==0)

{

if(pp<0)

{

perror("Error");

exit(0);

}

else if (pp==0)

{

if(rlflag==1)

{

FILE *fp=fopen(in1,"r");

dup2(fileno(fp),0);

fclose(fp);

}

if(rgflag==1)

{

FILE *fp=fopen(out1,"w+");

dup2(fileno(fp),1);

fclose(fp);

}

int val=execvp(arr[0],arr);

if(val<0)

{

perror("Command not found");

exit(0);

}

}

else

{ int s;

waitpid(pp,&s,WUNTRACED);

if(WIFSTOPPED(s))

{

strcpy(procs[counters].name,arr[0]);

procs[counters].pid=pp;

procs[counters++].status=1;

}

}

}

else if (flag==1)

{

if(pp<0)

{

perror("Error");

exit(0);

}

else if (pp==0)

{ if(rlflag==1)

{

FILE *fp=fopen(in1,"r");

dup2(fileno(fp),0);

}

if(rgflag==1)

{

FILE *fp=fopen(out1,"w+");

dup2(fileno(fp),1);

}

int val=execvp(arr[0],arr);

if(val<0)

{

perror("Command Not Found");

exit(0);

}

}

else

{

strcpy(procs[counters].name,arr[0]);

if((strcmp(arr[0],"gedit")==0||strcmp(arr[0],"emacs")==0)&&arr[1]!=NULL)

strcpy(procs[counters].name2,arr[1]);

procs[counters].pid=pp;

procs[counters++].status=1;

}

}

dup2(sout,1);

dup2(sin,0);

close(sout);

close(sin);

}

int pflag=0,lo=0;

//Function for displaying prompt

void prompt()

{

char *username,*cwd=NULL,hostname[100],finalpath[1000];

strcpy (finalpath,"~");

username=getenv("USER");

gethostname(hostname,100);

cwd=getcwd(cwd,1000);

char *path=strstr(cwd,source);

if(path==NULL)

{

printf("%s@%s:%s> ",username,hostname,cwd);

return;

}

path=path+strlen(source);

strcat(finalpath,path);

printf("%s@%s:%s> ",username,hostname,finalpath);

return;

}

int rgflag,rlflag;

//Function for implementing cd command

void changedir(char *arr[])

{

char *cwd='\0',pres[10000],arg[10000];

if ((arr[1]==NULL) || (!strcmp(arr[1],"~")) || (!strcmp(arr[1],"~/")))

{

if(chdir(source))

perror("chdir()");

else

return;

}

else

{

strcpy(arg,arr[1]);

}

cwd = getcwd(cwd,1000);

strcpy(pres,cwd);

strcat(pres,"/");

strcat(pres, arr[1]);

if(chdir(pres))

perror("chdir()");

else

return;

}

//Function for parsing with redirection handling included

int point;int i,j;

void parse(char input[],char *arr[])

{

for(lo=0;lo<i;lo++)

if(input[lo]=='|')

{

pflag=1;

break;

}

for(lo=0;lo<i;lo++)

if(input[lo]=='<')

{

rlflag=1;

break;

}

for(lo=0;lo<i;lo++)

if(input[lo]=='>')

{ rgflag=1;

break;

}

int i,j;ctr=0;

char input3[10000];

strcpy(input3,input);

char input4[10000];

strcpy(input4,input);

char *part=strtok(input,seps);

while(part!='\0')

{

arr[ctr]=part;

if(!strcmp(part,">"))

{

arr[ctr]='\0';

point=ctr;

}

else if(!strcmp(part,"<"))

{

arr[ctr]='\0';

point=ctr;

}

ctr++;

part=strtok(NULL,seps);

}

arr[ctr]='\0';ctr++;

if(rlflag==1)

{

char sep[]="<";

char *part=strtok(input3,sep);

part=strtok(NULL,sep);

char *part2;

part2=strtok(part,seps);

in1=part2;

}

if(rgflag==1)

{

char sep1[]=">";

char *part1=strtok(input4,sep1);

part1=strtok(NULL,sep1);

char *part3=strtok(part1,seps);

out1=part3;

}

return;

}

//Function for handling background processes

void child(int signum)

{

int p,i=0,count=0;

p = waitpid(WAIT_ANY, NULL, WNOHANG);

for(i=0;i<counters;i++)

{

if(procs[i].pid==p)

{

int j=0;

fflush(stdout);

printf("\n%s %d exited normally\n",procs[i].name,procs[i].pid);

prompt();

fflush(stdout);

procs[i].status=0;

}

}

signal(SIGCHLD, child);

return;

}

//Function for handling signals

void signalhandling(int signum)

{

if(signum==20)

kill(pp,20);

if(signum==2 || signum ==3)

{

fflush(stdout);

printf("\n");

prompt();

fflush(stdout);

signal(SIGINT, signalhandling);

signal(SIGQUIT, signalhandling);

signal(SIGTSTP,signalhandling);

}

return;

}

int main ()

{

signal(SIGINT,SIG_IGN);

signal(SIGINT,signalhandling);

signal(SIGCHLD,SIG_IGN);

signal(SIGCHLD,child);

signal(SIGTSTP,SIG_IGN);

signal(SIGTSTP,signalhandling);

signal(SIGQUIT,SIG_IGN);

signal(SIGQUIT,signalhandling);

source=getenv("PWD");

pid_t main_pid=getpid();

//If-else satements for different commands

while(1)

{

prompt();

j=0;i=0;

char input[10000]={'\0'},ch;

char *arr[10000];

scanf("%c",&ch);

int sflag=0;

if(ch=='\n')

sflag=1;

while(ch!='\n')

{

if(ch=='&')

{

scanf("%c",&ch);

flag=1;

i--;

continue;

}

input[i++]=ch;

scanf("%c",&ch);

}

input[i]='\0';

char input1[10000];

strcpy(input1,input);

ctr=0;

rlflag=0;rgflag=0;pflag=0;

parse(input1,arr);

char input2[10000];

strcpy(input2,input);

if(arr[0]==NULL)

{

continue;

}

//When there are both pipes and redirection

if(pflag!=0)

{

char *baby = NULL, *arrs[1000];

int newPipe[2], oldPipe[2], pipesCount, aCount=0,i,status;

pid_t pid;char *ar[10000];

pipesCount = 0;

char *parts=strtok(input2,"|");

while(parts!=NULL)

{

arrs[pipesCount]=parts;

pipesCount++;

parts=strtok(NULL,"|");

}

arrs[pipesCount++]=parts;

pipesCount--;

int incop, outcop;

// creating copy of stdin and stdout

incop=dup(STDIN_FILENO);

outcop=dup(STDOUT_FILENO);

for(i = 0; i < pipesCount; i++)

// For each command

{

if(i < pipesCount-1)

pipe(newPipe);

// create a pipe

rlflag=0;rgflag=0;

parse(arrs[i],ar);

pid = fork();

if(i>0 && i<pipesCount-1)

{

dup2(oldPipe[0], 0);

close(oldPipe[1]);

close(oldPipe[0]);

}

else if(i==pipesCount-1)

//for last command.

{

dup2(oldPipe[0], 0);

close(oldPipe[1]);

close(oldPipe[0]);

}

if(pid == 0)

// Child

{

if(i==0)

{

dup2(newPipe[1], 1);

close(newPipe[0]);

close(newPipe[1]);

}

if(i>0 && i<pipesCount-1)

{

dup2(newPipe[1], 1);

close(newPipe[0]);

close(newPipe[1]);

}

if(rlflag==1)

{

FILE *fp=fopen(in1,"r");

dup2(fileno(fp),0);

}

if(rgflag==1)

{

int fp=open(out1,O_CREAT | O_WRONLY,0700);

dup2(fp,1);

}

int val=execvp(ar[0],ar);

if(val<0)

{

perror("Command Not Found");

exit(0);

}

}

else

{

waitpid(pid, &status, 0);

// saving pipes

if(i < pipesCount-1)

{

oldPipe[0] = newPipe[0];

oldPipe[1] = newPipe[1];

}

}

}

//restore stdin and stdout

close(oldPipe[0]);

close(newPipe[0]);

close(oldPipe[1]);

close(newPipe[1]);

dup2(incop, 0);

dup2(outcop, 1);

close(incop);

close(outcop);

continue;

}

//User Defined Commands

if (strcmp(arr[0],"quit")==0)

return;

else if(strcmp(arr[0],"cd")==0)

changedir(arr);

else if(strcmp(arr[0],"pinfo")==0&&arr[1]=='\0')

{

int p=getpid(),ank=0,anks=0;char a[100],b[100];

while(p!=0)

{

a[ank++]=(p%10+'0');

p/=10;

}

int k=0;

for(anks=ank-1;anks>=0;anks--)

{

b[k++]=a[anks];

}

b[k]='\0';

char fp[1000],fp2[1000];

strcpy(fp,"/proc/");

strcat(fp,b);

strcpy(fp2,fp);

strcat(fp,"/status");

FILE *fo;

char *l;

size_t len=0;

ssize_t re;

fo=fopen(fp,"r");

if(fo>0)

{

int ctr2=0;

while(re=getline(&l,&len,fo)!=-1)

{

if(ctr2==0||ctr2==1||ctr2==3||ctr2==11)

printf("%s",l);

ctr2++;

}

fclose(fo);

}

strcat(fp2,"/exe");

int nn;char ar[50];

nn=readlink(fp2,ar,50);

ar[nn]='\0';

printf("Executable Path: %s\n",ar);

// fo=fopen(fp,r);

// printf("%s\n",fp);

}

else if(strcmp(arr[0],"pinfo")==0)

{

//printf("The PID of Process is - %d\n",getpid());

int p=atoi(arr[1]),ank=0,anks=0;char a[100],b[100];

//printf("%s\n",arr[1]);

while(p!=0)

{

a[ank++]=(p%10+'0');

p/=10;

}

int k=0;

for(anks=ank-1;anks>=0;anks--)

{

b[k++]=a[anks];

}

b[k]='\0';

char fp[1000],fp2[1000];

strcpy(fp,"/proc/");

// printf("%s\n",b);

strcat(fp,b);

strcpy(fp2,fp);

strcat(fp,"/status");

//printf("%s\n",fp);

FILE *fo;

char *l;

size_t len=0;

ssize_t re;

fo=fopen(fp,"r");

if(fo>0)

{

int ctr2=0;

while(re=getline(&l,&len,fo)!=-1)

{

if(ctr2==0||ctr2==11||ctr2==1||ctr2==3)

printf("%s",l);

ctr2++;

}

fclose(fo);

}

else

{

printf("Invalid PID\n");

continue;

}

strcat(fp2,"/exe");

int nn;char ar[50];

nn=readlink(fp2,ar,50);

ar[nn]='\0';

printf("Executable Path: %s\n",ar);

// printf("%s\n",fp);

}

else if(strcmp(arr[0],"jobs")==0)

{

int ctr1=0,ctr5=0;

for(ctr1=0;ctr1<counters;ctr1++)

{

if(procs[ctr1].status==1)

{

if((strcmp(procs[ctr1].name,"gedit")==0||strcmp(procs[ctr1].name,"emacs")==0)&&arr[1]!=NULL)

printf("%d. %s %s [%d]\n",ctr5+1,procs[ctr1].name,procs[ctr1].name2,procs[ctr1].pid);

else

printf("%d. %s [%d]\n",ctr5+1,procs[ctr1].name,procs[ctr1].pid);

array[ctr5]=ctr1;

ctr5++;

}

}

}

else if(strcmp(arr[0],"kjob")==0)

{

int st;

/*int ctr1=0;

for(ctr1=0;ctr1<counters;ctr1++)

{

if(procs[ctr1].status==1)

{

//printf("%d. %s [%d]\n",ctr1+1,procs[ctr1].name,procs[ctr1].pid);

}

}*/

if(atoi(arr[1])-1>=counters||atoi(arr[1])-1<0)

{

printf("Wrong Index No.\n");

continue;

}

kill(procs[array[atoi(arr[1])-1]].pid,atoi(arr[2]));

}

else if(strcmp(arr[0],"overkill")==0)

{

int ctr1=0;

for(ctr1=0;ctr1<counters;ctr1++)

{

if(procs[ctr1].status==1)

kill(procs[ctr1].pid,9);

}

}

else if(strcmp(arr[0],"fg")==0)

{

int s;

procs[array[atoi(arr[1])-1]].status=0;

waitpid(procs[array[atoi(arr[1])-1]].pid,&s,0);

printf("%d %s exited normally\n",procs[array[atoi(arr[1])-1]].pid,procs[array[atoi(arr[1])-1]].name);

}

else

{

if(flag==1)

strcat(input,"&");

execs(arr,rlflag,rgflag);

}

flag=0;

}

return 0;

}