/*

* The following is part of the ICS231 Operating Systems

* Course at IIIT-Hyderabad

* It is part of the operating systems project.

* Author : Rajesh Vakkalagadda

* Roll No: 201001064

*

*

* Some Assumptions Taken:

* other commands : hist , !hist , hist+number (like hist1 , hist2) , pid , pidall , quit

*

*/

#include<stdio.h>

#include<string.h>

#include<sys/types.h>

#include<sys/wait.h>

#include<sys/stat.h>

#include<fcntl.h>

#include<stdlib.h>

#include<unistd.h>

#include<signal.h>

char *value,cwd[100],host[100],hist[100][100],home[100],pidname[100][100];

int histlen,pidnum[100],pidlen=0,flag[100],fore[100];

int running_foreground=0;

char hst[100];

int getnumber(char a[100])

{

int i,l=0;

char b[10];

for(i=0;i<strlen(a);i++) { if(a[i]=='h'&&a[i+1]=='i'&&a[i+3]=='t') { i=i+4; break; } }

while(a[i]>='0'&&a[i]<='9') b[l++]=a[i++];

b[l]='\0';

return atoi(b);

}

void handler(int sig)

{

int status;

int pid=wait(&status);

int i=0;

while (pidnum[i]!=pid) i++;

flag[i]=0;

if (fore[i]==0) printf("\n%s : Pid %d exited with status %d.\n", pidname[i],pid,status);

else running_foreground--;

signal(SIGCHLD,handler);

}

void pidall() { int i; for(i=0;i<pidlen;i++) { printf("%d: %s %d\n",i+1,pidname[i],pidnum[i]);} }

void pidcurrent() { int i; for(i=0;i<pidlen;i++) { if(flag[i]==1) { printf("%s %d\n",pidname[i],pidnum[i]); } } }

void history(char command[100])

{

int num,i,j,k;

if(strstr(command,"hist")!=NULL && strlen(command)==4) {

for(i=0;i<histlen-1;i++)

printf("%d %s\n",i+1,hist[i]);

}

else if(strstr(command,"!")==NULL) {

num=getnumber(command);

k=histlen-num-1;

if(k < 0) k=0;

else if(num > histlen) k=0;

for(i=k;i<histlen-1;i++) printf("%d %s\n",i-(k-1),hist[i]);

}

else {

histlen--;

num=getnumber(command);

char com[100];

if(num > histlen) num=histlen;

strcpy(com,hist[num-1]);

strcpy(hst,com);

}

}

void cd(char command[100])

{

char tempstr[100],*test,*str[100];

int stlen=0;

strcpy(tempstr,command);

test=strtok(tempstr," \t");

while(test!=NULL) { str[stlen++]=test; test=strtok(NULL," \t"); }

str[stlen]=test;

int i,j,k;

char t[100];

if(str[1]==NULL) str[1]=home;

int r=chdir(str[1]);

if(r!=0) printf("path not found or the file has no suitable permisiions\n");

getcwd(cwd,100);

if(strstr(cwd,home)!=NULL) {

k=0;

t[k++]='~';

i=strlen(home);

for(j=i;j<strlen(cwd);j++) t[k++]=cwd[j];

t[k]='\0';

strcpy(cwd,t);

}

}

void exvp(char **str)

{

execvp(str[0],str);

printf("%s is wrong or it has occured an error\n",str[0]);

exit(EXIT_FAILURE);

}

void pidpro(){ printf("Command name: a.out process id %d\n",getpid()); }

void lessmore(char *command)

{

int i,j,k,len=0,f=0;

char *test,*a[100];

if(strstr(command,">") && strstr(command,"<")) f=2;

else if(strstr(command,">")!=NULL) f=1;

test=strtok(command,"<>");

while(test!=NULL) { a[len++]=test; test=strtok(NULL,"<>"); }

a[len]=test;

char *b[100],l=0;

test=strtok(a[0]," \t");

while(test!=NULL)

{

b[l++]=test;

test=strtok(NULL," \t");

}

b[l]=test;

if(f==0||f==2) { a[1]=strtok(a[1]," "); FILE *in; in=freopen(a[1],"r",stdin); }

if(f==1) { a[1]=strtok(a[1]," "); FILE *out; out=freopen(a[1],"w",stdout); }

else if(f==2) { a[2]=strtok(a[2]," "); FILE *out; out=freopen(a[2],"w",stdout); }

if(strstr(b[0],"hist")!=NULL) history(b[0]);

else if(strstr(b[0],"pid")!=NULL) {

if(l==1) pidpro();

else if(l==2 && strstr(b[1],"all")!=NULL) pidall();

else pidcurrent();

}

else exvp(b);

exit(0);

}

void check(char command[100])

{

int i,j,k;

char t[100];

int stlen=0;

char *test,tempstr[100],*str[100];

strcpy(t,command);

for(i=0;i<strlen(command);i++) {

if(command[i]=='~') {

k=i+1;

j=0;

while(home[j]!='\0')

command[i++]=home[j++];

for(j=k;j<=strlen(command);j++)

command[i++]=t[j];

i=k-1;

}

}

strcpy(tempstr,command);

test=strtok(tempstr," \t");

while(test!=NULL) { str[stlen++]=test; test=strtok(NULL," \t"); }

str[stlen]=test;

if(strstr(command,">")==NULL && strstr(command,"<")==NULL && strstr(command,"|")==NULL) {

if(strstr(command,"hist")!=NULL) history(str[0]);

else if(strstr(command,"pid")==NULL&&strstr(command,"&")==NULL)

exvp(str);

else if(strstr(command,"&")!=NULL){

str[stlen-1] = NULL;

exvp(str);

}

else if(strstr(str[0],"pid")!=NULL){

if(stlen==1) pidpro();

else if(stlen==2 && strcmp(str[1],"all")==0) pidall();

else pidcurrent();

}

}

else if((strstr(command,"<")!=NULL || strstr(command,">")!=NULL) && strstr(command,"|")==NULL) lessmore(command);

}

int main()

{

signal(SIGCHLD, handler);

signal(SIGQUIT, SIG_IGN);

signal(SIGABRT, SIG_IGN);

signal(SIGINT, SIG_IGN);

signal(SIGTSTP, SIG_IGN);

histlen=0;

pidlen=0;

int u=0;

getcwd(home,100);

strcpy(cwd,"~");

gethostname(host,100);

value=getenv("USER");

while(1)

{

int i,j;

char command[100];

printf("<%s@%s:%s> ",value,host,cwd);

command[0]='\0';

i=scanf("%[^\n]",command);

getchar();

if (i!=1) continue;

x: strcpy(hist[histlen++],command);

int foreground=(strstr(command,"&")==NULL?1:0);

if (strstr(command,"quit")!=NULL) exit(1);

else if (strstr(command,"cd")!=NULL) cd(command);

else if (strstr(command,"!hist")!=NULL) { history(command); strcpy(command,hst); goto x;}

else{

char temp[100],*arr[100];

int alen=0;

strcpy(temp,command);

char *tok;

tok=strtok(temp,"|");

while(tok!=NULL)

{

arr[alen] = (char*)malloc(1000*sizeof(char));

strcpy(arr[alen++],tok);

tok=strtok(NULL,"|");

}

arr[alen]=NULL;

if (foreground) running_foreground=alen;

else running_foreground=0;

int **pipefd;

if (alen>1) pipefd=(int **)malloc(sizeof(int *)*alen-1);

for (i=0;i<alen-1;i++) { pipefd[i]=(int *)malloc(sizeof(int)*2); pipe(pipefd[i]); }

for(i=0;i<alen;i++) {

int pid=fork();

if(pid==0) {

for (j=0; j<alen-1; j++) {

if (j!=i) close(pipefd[j][1]);

else dup2(pipefd[j][1],STDOUT_FILENO);

if (j!=i-1) close(pipefd[j][0]);

else dup2(pipefd[j][0],STDIN_FILENO);

}

check(arr[i]);

exit(EXIT_SUCCESS);

}

else {

arr[i]=strtok(arr[i]," \t");

strcpy(pidname[pidlen],arr[i]);

flag[pidlen]=1;

if (foreground) fore[pidlen]=1;

pidnum[pidlen++]=pid;

}

}

for(i=0;i<alen-1;i++) { close(pipefd[i][0]); close(pipefd[i][1]); free(pipefd[i]); }

if (alen>1) free(pipefd);

while(running_foreground) pause();

}

}

return 0;

}