laal_shell.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>		//for getXXX() func
#include <sys/types.h>	//For wait
#include <sys/wait.h>	//for wait
#include <signal.h>
#include <setjmp.h>
#include <fcntl.h>	//For file control
#include <limits.h>
#include <sys/utsname.h>
#include <sys/stat.h>
#include <dirent.h>
#include <sys/dir.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <locale.h>


char ipfile[100], opfile[100];
char *input; size_t inputsize = 500;
int mflag, njobs=0, jobnumber[1000000], ctrZ_flag, bg_flag;
sigjmp_buf ctrlz_buf;
struct stat bufferc;
int stdout1, stdin1;
char ta = 't';
typedef struct jobs
{
	pid_t pid;
	char name[50];
}jobs;
jobs job[1000000];

// function to remove any extra white spaces from the command
char* whitespaces(char str[]) {
	char *arr = str;
	int i,j=0;

	for(i=0; i<strlen(arr); i++) {
		if(arr[i]=='\t') arr[i]=' ';
	}

	for (i=0;i<strlen(str);i++) {
		if (str[i] == ' ') {
			for (; str[i] == ' '; i++);
			i--;
		}
		arr[j] = str[i];
		j++;
		if (arr[0] == ' ') j--;
	}
	if (arr[j-1] == ' ') arr[j-1] = '\0';
	else arr[j] = '\0';

	return arr;
}

int tokeniser(char input3[], char list[][30], char* t) {
	char *token;
	token=strtok(input3,t);
	int i=0;

	while(token)
	{
		sprintf(list[i++], "%s", token);
		token=strtok(NULL, t);
	}
	return i;
}

int custom_pwd(char* pwd) {
	char *token;
	char dir[30][30], temp[30];
	sprintf(temp, "%s", pwd);
	int i=0,j,err;
	for (token=strtok(temp,"/"); token != NULL; token=strtok(NULL, "/"), i++)
		sprintf(dir[i], "%s",token);
	sprintf(pwd, "/%s", dir[i-1]);
	return 0;
}

int getPS(char mwd[]) {
	char *username = (char *) malloc(30*sizeof(char));
	username = getenv("USER");
	struct utsname system_info;
	uname(&system_info);
	char *pwd=malloc(1000*sizeof(char));
	getcwd(pwd, 100);
	if(strcmp(mwd,pwd)!=0) custom_pwd(pwd);
	else pwd[0] = '\0';
	printf("%s @ %s :~%s $ ", username, system_info.sysname, pwd);
	return 0;
}

pid_t multipleCommands(char input[]) {
	char list[10][30];
	int status;
	pid_t temp_pid,temp2_pid;

	int n_args=tokeniser(input, list, ";");				//To check for multiple commands

	mflag=0;
	if(n_args>1) {
		int k;
		mflag=1;
		for(k=0; k<n_args; k++) {
			sprintf(input, "%s", list[k]);
			temp_pid=fork();
			if(temp_pid==0)								//child process in multiple command
				return temp_pid;
			if(temp2_pid=wait(&status) < 0) _exit(1);
			else if (temp_pid > 0) {
				temp2_pid=wait(&status);
				continue;
			}
		}
		return -1;
	}
	return -2;
}

void remove_job(pid_t pid) {
	int jno = jobnumber[pid]; 		//To get jobnumber of process which got ctr+Z
	int ptr;
	for(ptr=jno; ptr<njobs-1; ptr++) {
		job[ptr]=job[ptr+1];
		jobnumber[job[ptr].pid]--;
	}
	njobs--;
}

int getiofile(char input[], int in) {
	int i = 0;
	if (in == 1) {
		for(i=0; i < strlen(input); i++) {
			if(input[i]=='<') {
				for (; input[i+1] == ' '; i++);
				break;
			}
		}
		int x = 0;
		for (i++; input[i] != '>' && input[i] != ' ' && input[i] != '\n'; i++, x++)
			ipfile[x] = input[i];
		ipfile[x+1] = '\0';
	}
	else {
		for(i=0; i < strlen(input); i++) {
			if(input[i]=='>') {
				if (input[i+1] == '>') {ta = 'a'; i++;}
				for (; input[i+1] == ' '; i++);
				break;
			}
		}
		int x = 0;
		for (i++; input[i] != '<' && input[i] != ' ' && input[i] != '\n'; i++, x++)
			opfile[x] = input[i];
		opfile[x+1] = '\0';
	}
	printf("..in=%s..out=%s..\n", ipfile, opfile);
	return 0;
}

int outputdup(char *fileout) {
	printf("ta=%c..\n", ta);
	int fout;
	//printf("%s\n", fileout);
	if (stat(fileout, &bufferc) == 0 && access(fileout,W_OK)!=0) {
		printf("You dont have permission to access %s\n",fileout);
		return 1;
	}
	else {
		if(stat(fileout, &bufferc))				//write permissions only for user
			creat(fileout,0644);
		if (ta == 't')
			fout = open(fileout, O_WRONLY | O_TRUNC, 0644);
		else fout = open(fileout, O_WRONLY | O_APPEND, 0644);
		stdout1 = dup(1);
		dup2(fout, 1);
		close(fout);
	}
	return 0;
}

int inputdup(char *filein) {
	int fin;
	if(stat(filein, &bufferc)!=0) {
		printf("File %s doesn't exist\n",filein);
		return 1;
	}
	else if(access(filein,R_OK)!=0) {
		printf("You dont have permission to access %s\n",filein);
		return 1;
	}
	else {
		fin=open(filein,O_RDONLY,0644);			//opening file in RDONLY with permissions
		stdin1 = dup(0);
		dup2(fin, 0);
		close(fin);
	}
	return 0;
}

void iowork(char input[]) {
	int k = 0;
	ipfile[0]='\0';
	opfile[0]='\0';
	for(k=0; k<strlen(input);k++) {
		if(input[k]=='>') {
			getiofile(input, 1);
			break;
		}
	}
	for(k=0; k<strlen(input);k++) {
		if(input[k]=='<') {
			getiofile(input, 0);
			break;
		}
	}
}
//To execute piped commands
void pipe_commands(char input[]) {
	char list[10][30],parse[100], *token, ptr, temp[10][30];
	//char *input2=malloc(1000*sizeof(char));
	int i, j,k, num=0, fd[2], argc=0, status, fin,fout, in=0;
	pid_t pid;

	//To tokenise wrt "|"
	num=tokeniser(input, list, "|");

	for(i=0; i<num; i++) {
		bg_flag=0;				//For each subpart, bg_flag=0

		//Checking for ip and op file
		iowork(list[i]);

		//sscanf(list[i],"\n%[^<>]", input2);
		for (k = 0; k < strlen(list[i]); k++) {
			if (k == '>' || k == '<' || k == '\n' || k == '\0') break;
			input[k] = list[i][k];
		}
		input[k] = '\0';

		input=whitespaces(input);
		sprintf(parse, "%s",input);						//Keep extra copy of input in input2

		//Tokenise each subpart of pipe into temp, parse is destroyed by strtok
		argc=tokeniser(parse,temp," ");

		char **argv=malloc(1000*sizeof(char*));
		for (j = 0; j < argc; j++) {
			argv[j] = temp[j];
		}

		if(strcmp(temp[argc-1], "&") == 0) {
			bg_flag=1;							//Implies command is a bg
			temp[argc-1][0] = '\0';
			argc--;
		}

		pipe(fd);					//Make a pipe

		pid=fork();

		if(pid==0) {
			if(fd<0)
				printf("Pipe error\n");
			else {
				if(fd[0]!=0)			//As long as input is not stdin1, duplicate it as read end of the pipe
				{
					dup2(in, 0);
					close(fd[0]);
				}
				if(i!=num-1)
				{
					dup2(fd[1], 1);				//Except for last one, output is to write end of the pipe
					close(fd[1]);
				}
				int ret = 0;
				//If input redirection is there in subpart of pipe
				if(ipfile[0]!='\0') {
					ret = 0;
					ret = inputdup(ipfile);
					if (ret == 1)  { continue; }
				}
				//If op redirection is there in subpart of pipe
				if(opfile[0]!='\0') {
					ret = 0;
					ret = outputdup(opfile);
					if (ret == 1) { continue; }
				}

				//If subpart of pipe is echo
				if(strcmp(temp[0],"echo")==0) {
					int stdout1;
					if(opfile[0]!='\0') {
						ret = 0;
						ret = outputdup(opfile);
						if (ret == 1) { continue; }
					}
					for(k=1; k<argc; k++)
						for(j=0; j<strlen(temp[k]); j++)
							printf("%c", temp[k][j]);
					printf("\n");

					dup2(stdout1,1);		//After redirecting output to file, control regained by stdout1
					_exit(1);
				}
				else {
					printf("..%s..\n", argv[0]);
          execvp(argv[0], argv);			//execute normal subparts in pipe
					_exit(1);
				}
			}		//else of (fd<0)
		}			//end of pid==0

		else if(pid>0) {
			if(fd<0)
				printf("Pipe error\n");
			else {
				job[njobs].pid=pid;			//current process pid
				sprintf(job[njobs].name, "%s", temp[0]);
				jobnumber[pid] = njobs;
				njobs++;

				if(bg_flag!=1) {
					ctrZ_flag=0;
					waitpid(pid,&status,WUNTRACED);
					if(pid < 0) {
						_exit(1);
					}
					if (pid==0);
					if(ctrZ_flag==0)
						remove_job(pid);			//no ctrl Z pressed, job done
				}
				else
					printf("[%d] %s \n",job[njobs-1].pid, job[njobs-1].name);
				close(fd[1]);
				in=fd[0];
			}
		}
	}	//End of for oop
}			//End of function

int pinfo_fn(char *process) {
    int i = 0;
    FILE *fd;
    char add[100];
    char text[100],exe[100],state,size[10],extra_arr[100] = "a";
    for (i = 0; i < 100; i++)
        add[i] = '\0';
    add[0] = '/'; add[1] = 'p'; add[2] = 'r'; add[3] = 'o'; add[4] = 'c'; add[5] = '/'; add[6] = '\0';
    //printf("Process==%s...\n", process);
    if (process[0] == '\0') {
			sprintf(process, "%d", getpid());
		}
    //copy
    printf("Pid -- %s\n",process);
    for (i = 0; process[i] != '\0'; i++)
        add[6+i] = process[i];
    add[6+i] = '\0';
    strcpy(exe,add);
    for (i = 0; add[i] != '\0'; i++);
    exe[i] = '/'; exe[i+1] = 'e'; exe[i+2] = 'x'; exe[i+3] = 'e'; exe[i+4] = '\0';
    for (i = 0; add[i] != '\0'; i++);
    add[i] = '/'; add[i+1] = 's'; add[i+2] = 't'; add[i+3] = 'a'; add[i+4] = 't'; add[i+5] == '\0';//add[i+5] = 'u'; add[i+6] = 's'; add[i+7] = '/'; add[i+8]  = '\0';
    fd = fopen(add, "r");
    if (fd == NULL) {
        printf("Process does not exist.\n"); return 0;
    }
    //printf("%s...\n", add);
    fscanf(fd, "%s", text);
    fscanf(fd, "%s", text);
    fscanf(fd, "%s", text);
    printf("Process Status -- %s\n", text);
    for (i = 0; add[i] != '\0'; i++);
    add[i] = 'm'; add[i+1] = '\0';
    fd = fopen(add, "r");
    if (fd == NULL) {
        printf("Process does not exist.\n"); return 0;
    }
    fscanf(fd, "%s", text);
    printf("Memory -- %s\n",text);
    //printf("exe==%s\n", exe);
    printf("Executable -- ");
    int ret = readlink(exe,extra_arr,100);
    printf("%s\n",extra_arr);
    return 0;
}


void signalHandlerc(int sig_num) {
	signal(SIGINT, signalHandlerc);
	printf("ctrl c pressed \n");
	fflush(stdout);
}
void signalHandlerz(int sig_num) {
	signal(SIGTSTP, signalHandlerz);
	printf("ctrl z pressed \n");
	fflush(stdout);
}

int main() {
	pid_t Mpid = getpid();
	char *input = malloc(1000*sizeof(char));
	char *input2=malloc(1000*sizeof(char));
	char mwd[100], pwd[100], p[10][30];
	pid_t pid, cpid,err;
	int i,len,j,status,k,a,argc, fin,fout;

	getcwd(mwd, 100);

	signal(SIGINT, signalHandlerc);
	signal(SIGTSTP, signalHandlerz);

	while(1) {
		getPS(mwd);						//Prints prompt

		input[0]='\0';
		ipfile[0]='\0';
		opfile[0]='\0';
		ta = 't';

		getline(&input, &inputsize , stdin);
		input[strlen(input)-1] = '\0';

		//scanf(" %[^\n]s",input);
		sprintf(input2, "%s", input);
		pid_t mpid = multipleCommands(input);
		if ( mpid == -1) continue;

		//Piper check comes here
		int piper=0, pipflag=0;
		for(i=0;i<strlen(input); i++) {
			if (pipflag == 1) {break;}
			if(input[i]=='|') {
				piper=1;
				pipe_commands(input);
				pipflag=1;
			}
		}
		if(piper==1 && mpid==0 && mflag==1)			//If pipe in multiple commands
			exit(10);

		else if(piper==1 && mflag==0)				//0 Multiple commands and piping involved
			continue;

		ipfile[0]='\0';
		opfile[0]='\0';
		for(i=0; i<strlen(input);i++) {
			if(input[i]=='<') getiofile(input, 1);			//atmax one same type char ""<>""
			else if (input[i] == '>') getiofile(input, 0);
		}

		for (int ite = 0; ite < strlen(input) && input[ite] != '<' && input[ite] != '>'; ite++)
			input2[ite] = input[ite];
		input2 = whitespaces(input2);
		sprintf(input, "%s", input2);
		//printf("..%s..\n", input);
		if(strcmp(input,"exit")==0 || strcmp(input,"quit")==0) {
			printf("Exiting shell BYE BYE\n\n");
			kill(Mpid, 9);
		}

		if(input[0]=='\0' || input[0]=='\n'){
			printf("\n");
			continue;
		}

		if(strcmp(input, "pwd")==0) {
			if(opfile[0]!='\0')  {
				if (outputdup(opfile) == 1) continue;
			}
			getcwd(pwd,100);
			printf("%s\n", pwd);
			dup2(stdout1,1);
			//printf("kmkdvkmskdfmmkf fkm km\n");
		}

		else {
			bg_flag=0;
			if(input[strlen(input)-1] ==  '&') {
				bg_flag=1;							//Implies command is a bg
				input[strlen(input)-2] = '\0';
			}
			//printf("input = %s..\n", input);
			argc=tokeniser(input,p, " ");			//For argument list

			if (strcmp(p[0], "pinfo") == 0) {
				pinfo_fn(p[1]);
			}
			//cd
			if(strcmp(p[0], "cd")==0) {
				if (argc == 1)
					chdir(mwd);
				else if(argc > 1) {
					if (p[1][0] == '~' && p[1][1] == '\0') { chdir(mwd); }
					else {
						DIR *dir = opendir(p[1]);
						if (dir) { closedir(dir); chdir(p[1]); }
						else printf("No such directory exists\n");
					}
				}
				else
					printf("No such directory exists\n");
				getcwd(pwd, 100);
			}

			//echo
			else if(strcmp(p[0], "echo")==0) {
				if(opfile[0] != '\0') {
					if (outputdup(opfile) == 1) continue;
				}
				for(k=1; k<argc && p[k][0] != '>' && p[k][0] != '<'; k++) {
					for(j=0; j<strlen(p[k]); j++)
						printf("%c", p[k][j]);
					printf(" ");
				}
				printf("\n");
				dup2(stdout1,1);
			}

			//jobs
			else if (strcmp(p[0], "jobs")==0) {
				//printf("njobs = %d\n", njobs);
				if (njobs == 0)
					printf("No jobs to show\n");
				if(njobs > 0) {
					for(i = 0; i < njobs; i++) {
						char addr[100] = "/proc/";
						char arrtemp[100];
						sprintf(arrtemp, "%d" ,job[i].pid);
						strcat(addr, arrtemp);
						strcat(addr, "/stat");
						char text[100];
						FILE *fd;
						fd = fopen(addr, "r");
						fscanf(fd, "%s", text);
    				fscanf(fd, "%s", text);
    				fscanf(fd, "%s", text);
						if (text[0] == 'R') {sprintf(text, "Running");}
						else if (text[0] == 'S') {sprintf(text, "Stopped");}
						printf("[%d] %s %s [%d]\n",i+1, job[i].name, text, job[i].pid);
						free(fd);
					}
				}
			}

			//kjob
			else if (strcmp(p[0],"kjob")==0) {
				//printf("argc=%d\n",argc);
				if (argc == 3) {
					int sig = atoi(p[2]);
					int j_no = atoi(p[1])-1;
					if (j_no < njobs) {
						kill(job[j_no].pid, sig);
						remove_job(job[j_no].pid);
					}
					else printf("No such job exists such as %d\n", j_no);
				}
				else printf("Wrong usage of kjob\n");
			}


			//overkill
			else if (strcmp(p[0], "overkill")==0) {
				stdout1 = dup(1);
				if(opfile[0] != '\0') {
					if (outputdup(opfile) == 1) continue;
				}
				if (njobs == 0) printf("No jobs to kill\n");
				else {
					for(i=0; i<njobs; i++) {
						printf("[%d] %s [%d] killed \n", i+1, job[i].name, job[i].pid);
						kill(job[i].pid, 9);
						remove_job(job[i].pid);
					}
					sleep(10);
				}
				dup2(stdout1,1);
				printf("Done\n");
			}

			//fg
			else if (strcmp(p[0], "fg")==0) {
				if (argc == 2) {
					int j_no= atoi(p[1]) - 1;
					if (j_no < njobs) {
						int status;
						ctrZ_flag=0;
						kill(job[atoi(p[1])-1].pid , SIGCONT);
						pid_t pid = waitpid(job[atoi(p[1])-1].pid, &status, WUNTRACED);

						if(ctrZ_flag==1) {
							printf("%s with pid:%d killed\n",job[j_no].name,pid);
							remove_job(job[i].pid);
							sleep(0);
						}
					}
					else printf("No such job exists\n");
				}
				else printf("Wrong usage of fg\n");
			}
			//bg
			else if (strcmp(p[0], "bg")==0) {
				if (argc == 2) {
					int j_no=atoi(p[1])-1;
					if (j_no < njobs) {
						kill(job[atoi(p[1])-1].pid , SIGCONT);
					}
				}
				else printf("No shuch job exists\n");
			}

			//setenv
			else if(strcmp(p[0], "setenv")==0) {
				if (argc == 3) {
					setenv(p[1], p[2], 1);
					printf("Environment variable set:: %s : %s\n", p[1], p[2]);
				}
				else printf("Wrong usage of setenv\n");
			}

			//unsetenv
			else if (strcmp(p[0], "unsetenv")==0) {
				if (argc == 2) {
					unsetenv(p[1]);
					printf("Environment variable unset:: %s\n", p[1]);
				}
				else printf("Wrong usage of unsetenv\n");
			}
			//Need to use exec
			else {
				//pid=fork();
				char **argv=malloc(265*sizeof(char*));
				for (j = 0; j < argc && p[j][0] != '<' && p[j][0] != '>'; j++) { argv[j]=p[j]; }
				//for (int ite = 0; ite < argc; ite++) printf("argv[%d] = %s\n", ite, argv[ite]);
				pid = fork();
				if(pid > 0) {
					job[njobs].pid = pid;			//current process pid
					sprintf(job[njobs].name, "%s", p[0]);
					jobnumber[pid] = njobs;
					njobs++;

					if(bg_flag != 1) {
						//printf("not background\n");
						ctrZ_flag = 0;
						waitpid(pid,&status,WUNTRACED);
						if(pid < 0) {
							perror("Error!");
							_exit(1);
						}
						if(ctrZ_flag==0) {
							remove_job(pid);			//no ctrl Z presses, job done
							kill(pid,9);
						}
						else if (ctrZ_flag==1);
					}
					else
						printf("[%d] %s \n",job[njobs-1].pid, job[njobs-1].name);
				}
				else if (pid==0) {
					if(ipfile[0]!='\0') {
						if (inputdup(ipfile) == 1) continue;
					}
					if(opfile[0]!='\0') {
						if (outputdup(opfile) == 1) continue;
					}

					execvp(argv[0], argv);						//removed err
					dup2(stdin1, 0);
					dup2(stdout1, 1);
					_exit(1);
				}
			}
		}
		if(mpid==0 && mflag==1) {		//in multiple command, if child is done, return to its parent for loop
			exit(16);
		}
	}
  return 0;
}