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PrunedNeuron/shell.c

Created April 3, 2019 16:49
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UNIX shell written in C.
Raw
shell.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <math.h>
#include <string.h>
#include <sys/wait.h>
#include <dirent.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>
#include <fcntl.h>
#include <grp.h>
#include <pwd.h>
#define rep(i, a, b) for(i = a; i < b; i++)
#define rev(i, a, b) for(i = a; i > b; i--)
#define TOK_BUFFER 64
#define COMM_BUFFER 64
#define TOK_DELIM " \t\n\a\r"
#define COMM_DELIM ";"
char* root;
int shell_cd (char **args);
int shell_exit (char **args);
int shell_quit(char **args);
int shell_pwd (char **args);
int shell_echo (char **args);
int shell_pinfo (char **args);
int shell_ls (char **args);
int shell_setenv (char **args);
int shell_unsetenv (char **args);
char *builtin_arr[] = {"cd","exit","pwd","echo","pinfo", "ls","setenv","unsetenv","quit"};
int (*builtin_functions[])(char**) = {&shell_cd,&shell_exit,&shell_pwd,&shell_echo,&shell_pinfo,&shell_ls,&shell_setenv,&shell_unsetenv,&shell_quit};
void sigintHandler(int sig_num) {
signal(SIGINT,sigintHandler);
fflush(stdout);
}
void pipehandler(char **args){
// File descriptors
int filedes[2];
int filedes2[2];
int num_cmds = 0;
char *command[256];
pid_t pid;
int err = -1,end = 0, i = 0, j = 0,k = 0,l = 0;
while (args[l] != NULL){
if (strcmp(args[l],"|") == 0){
num_cmds++;
}
l++;
}
num_cmds++;
while (args[j] != NULL && end != 1){
k = 0;
while (strcmp(args[j],"|") != 0){
command[k] = args[j];
j++;
if (args[j] == NULL){
end = 1;
k++;
break;
}
k++;
}
command[k] = NULL;
j++;
if (i % 2 != 0){
pipe(filedes);
}else{
pipe(filedes2);
}
pid=fork();
if(pid==-1){
if (i != num_cmds - 1){
if (i % 2 != 0){
close(filedes[1]); // for odd i
}else{
close(filedes2[1]); // for even i
}
}
printf("Child process could not be created\n");
return;
}
if(pid==0){
if (i == 0){
dup2(filedes2[1], STDOUT_FILENO);
}
else if (i == num_cmds - 1){
if (num_cmds % 2 != 0){
dup2(filedes[0],STDIN_FILENO);
}else{
dup2(filedes2[0],STDIN_FILENO);
}
}else{
if (i % 2 != 0){
dup2(filedes2[0],STDIN_FILENO);
dup2(filedes[1],STDOUT_FILENO);
}else{
dup2(filedes[0],STDIN_FILENO);
dup2(filedes2[1],STDOUT_FILENO);
}
}
if (execvp(command[0],command)==err){
kill(getpid(),SIGTERM);
}
}
if (i == 0){
close(filedes2[1]);
}
else if (i == num_cmds - 1){
if (num_cmds % 2 != 0){
close(filedes[0]);
}else{
close(filedes2[0]);
}
}else{
if (i % 2 != 0){
close(filedes2[0]);
close(filedes[1]);
}else{
close(filedes[0]);
close(filedes2[1]);
}
}
waitpid(pid,NULL,0);
i++;
}
}
int redirect(char **args, int num)
{
char in[100],out[100],app[100];
int r = 0,pid,flag1=0,flag2=0,flag3=0;
args[num] = NULL;
pid = fork();
if (pid==0)
{
for (int i=0;i<num;i++)
{
if (strcmp(args[i],"<")==0)
{
args[i] = NULL;
strcpy(in,args[i+1]);
flag1 = 1;
}
if (args[i]!=NULL)
{
if (strcmp(args[i],">")==0)
{
args[i] = NULL;
strcpy(out,args[i+1]);
flag2 = 1;
}
}
if (args[i]!=NULL)
{
if (args[i][1]==62)
{
args[i] = NULL;
strcpy(app,args[i+1]);
flag3 = 1;
}
}
}
if (flag1)
{
int fd;
fd = open(in,O_RDONLY,0);
if (fd<0)
{perror("Could not open input file"); exit(0);}
dup2(fd,0);
close(fd);
}
if (flag2)
{
struct stat buf;
if (stat(out,&buf)==0)
{
int fo;
fo = open(out, O_WRONLY);
if (fo<0)
{perror("Could not open output file"); exit(0);}
dup2(fo,1);
close(fo);
}
else
{
int fo;
fo = creat(out,0644);
if (fo<0)
{perror("Could not create output file"); exit(0);}
dup2(fo,1);
close(fo);
}
}
if (flag3)
{
struct stat buffer;
if (stat(app,&buffer)==0)
{
int fa;
fa = open(app,O_APPEND | O_WRONLY);
if (fa<0)
{perror("Could not open output file"); exit(0);}
dup2(fa,1);
close(fa);
}
else
{
int fa;
fa = creat(app,0644);
if (fa<0)
{perror("Could not create output file"); exit(0);}
dup2(fa,1);
close(fa);
}
}
if (execvp(args[0],args)<0)
{r=1; printf("%s: Command doesn't exist\n", args[0]);}
}
else
{wait(NULL);}
if (r!=1)
{printf("%s with process id: %d exited normally\n",args[0],pid);}
return 1;
}
int shell_setenv (char **args) {
if (args[2] == NULL) args[2] = " ";
if (setenv(args[1],args[2],1) != 0) perror("shell");
return 1;
}
int shell_unsetenv (char **args) {
if (unsetenv(args[1]) != 0) perror("shell");
return 1;
}
int shell_cd (char** args) {
if (args[1] == NULL)
return 1;
else if (strcmp(args[1],"~")==0){
chdir(root);
}
else if (chdir(args[1]) != 0)
perror("SHELL");
return 1;
}
int shell_exit (char** args) {
return EXIT_SUCCESS;
}
int shell_quit (char** args) {
return EXIT_SUCCESS;
}
int shell_pwd (char** args) {
char *curr_dir = (char *)malloc(1000*sizeof(char));
getcwd(curr_dir, 1000);
printf("%s\n", curr_dir);
free(curr_dir);
return 1;
}
int shell_echo (char** args) {
int i = 1;
while(args[i] != NULL) {
printf("%s ", args[i]);
i++;
}
printf("\n");
return 1;
}
int shell_pinfo (char ** args) {
char Process[1000];
strcpy(Process, "/proc/");
if(args[1])
strcat(Process, args[1]);
else
strcat(Process, "self");
char Stats[100];
strcpy(Stats, Process); strcat(Stats, "/stat");
int error_number[3];
error_number[0] = 0;
FILE * stat = fopen(Stats, "r");
if(error_number[0]) {
fprintf(stderr, "Error reading %s: %s\n", Stats, strerror(error_number[0]));
return 1;
}
int pid; char status; char name[20];
fscanf(stat, "%d", &pid); fscanf(stat, "%s", name); fscanf(stat, " %c", &status);
printf( "pid: %d\n", pid);
printf( "Process Status: %c\n", status);
fclose(stat);
error_number[0] = 0;
strcpy(Stats, Process); strcat(Stats, "/statm");
FILE * mem = fopen(Stats, "r");
if(error_number[0]) {
fprintf(stderr, "Error reading %s: %s\n", Stats, strerror(error_number[0]));
return 1;
}
int memSize; fscanf(mem, "%d", &memSize);
fprintf(stdout, "Memory: %d\n", memSize);
fclose(mem);
char exePath[1000];
strcpy(Stats, Process); strcat(Stats, "/exe");
error_number[0] = 0;
readlink(Stats, exePath, sizeof(exePath));
if(error_number[0]) {
fprintf(stderr, "Error reading symbolic link %s: %s\n", Stats, strerror(error_number[0]));
return 1;
}
int sameChars = 0, baseL = strlen(root);
for(sameChars = 0; sameChars < baseL; sameChars++)
if(root[sameChars] != exePath[sameChars]) break;;
char relPath[1000];
if(sameChars == baseL) {
relPath[0] = '~'; relPath[1] = '\0';
strcat(relPath, (const char *)&exePath[baseL]);
}
else {
strcpy(relPath, exePath);
relPath[strlen(exePath)] = '\0';
}
int i = 0;
while(exePath[i]) exePath[i++] = '\0';
fprintf(stdout, "Executable Path: %s\n", relPath);
return 1;
}
int shell_ls (char** args) {
DIR* dir;
struct stat mystat[4];
struct passwd *user[2];
struct group *group[2];
char *buffer;
int count[6];
count[1] = 0;
count[2] = 0;
count[3] = 0;
count[4] = 1;
count[5] = 0;
unsigned char mod[13];
struct tm *starttime[2];
time_t now;
int year;
struct dirent **dient[4];
buffer = malloc(1024*sizeof(char));
while(args[count[4]] != NULL) {
count[5] = 0;
if (args[count[4]][count[5]] == 45) {
count[5] = 1;
while(args[count[4]][count[5]] != 0) {
if(args[count[4]][count[5]] == 108) count[1] = 1;
if(args[count[4]][count[5]] == 97) count[2] = 1;
count[5]++;
}
}
else {
if (count[4] > 0) count[3] = count[4];
}
count[4]++;
}
if (count[3] == 0 || args[count[3]] == NULL) args[count[3]] = ".";
count[0] = scandir(".",&dient[0],NULL,alphasort);
count[0] = scandir(args[count[3]],&dient[0],NULL,alphasort);
if (count[0] < 0) perror("shell");
else {
for(count[4]=0;count[4]<count[0];count[4]++) {
if (count[1] == 1) {
if (count[2] == 1) {
sprintf(buffer,"%s/%s",args[count[3]],dient[0][count[4]]->d_name);
stat(buffer,&mystat[0]);
printf( (S_ISDIR(mystat[0].st_mode)) ? "d" : "-");
printf( (mystat[0].st_mode & S_IRUSR) ? "r" : "-");
printf( (mystat[0].st_mode & S_IWUSR) ? "w" : "-");
printf( (mystat[0].st_mode & S_IXUSR) ? "x" : "-");
printf( (mystat[0].st_mode & S_IRGRP) ? "r" : "-");
printf( (mystat[0].st_mode & S_IWGRP) ? "w" : "-");
printf( (mystat[0].st_mode & S_IXGRP) ? "x" : "-");
printf( (mystat[0].st_mode & S_IROTH) ? "r" : "-");
printf( (mystat[0].st_mode & S_IWOTH) ? "w" : "-");
printf( (mystat[0].st_mode & S_IXOTH) ? "x" : "-");
printf(" \t%d",(int)mystat[0].st_nlink);
user[1] = getpwuid(mystat[0].st_uid);
printf(" \t%s", user[1]->pw_name);
group[1] = getgrgid(mystat[0].st_gid);
printf(" \t%s", group[1]->gr_name);
printf(" \t%lld",(long long)mystat[0].st_size);
time(&now);
year = localtime(&now)->tm_year;
starttime[1] = localtime(&mystat[0].st_ctime);
if(starttime[1]->tm_year == year)
strftime(mod,13,"%b %e %R",starttime[1]);
else
strftime(mod,13,"%b %e %Y",starttime[1]);
printf(" \t%s",mod );
printf(" \t%s\n",dient[0][count[4]]->d_name);
}
else {
if ((dient[0][count[4]] ->d_name)[0] != 46) {
sprintf(buffer,"%s/%s",args[count[3]],dient[0][count[4]]->d_name);
stat(buffer,&mystat[0]);
printf( (S_ISDIR(mystat[0].st_mode)) ? "d" : "-");
printf( (mystat[0].st_mode & S_IRUSR) ? "r" : "-");
printf( (mystat[0].st_mode & S_IWUSR) ? "w" : "-");
printf( (mystat[0].st_mode & S_IXUSR) ? "x" : "-");
printf( (mystat[0].st_mode & S_IRGRP) ? "r" : "-");
printf( (mystat[0].st_mode & S_IWGRP) ? "w" : "-");
printf( (mystat[0].st_mode & S_IXGRP) ? "x" : "-");
printf( (mystat[0].st_mode & S_IROTH) ? "r" : "-");
printf( (mystat[0].st_mode & S_IWOTH) ? "w" : "-");
printf( (mystat[0].st_mode & S_IXOTH) ? "x" : "-");
printf(" \t%d",(int)mystat[0].st_nlink);
user[1] = getpwuid(mystat[0].st_uid);
printf(" \t%s", user[1]->pw_name);
group[1]=getgrgid(mystat[0].st_gid);
printf(" \t%s", group[1]->gr_name);
printf(" \t%lld",(long long)mystat[0].st_size);
time(&now);
year = localtime(&now)->tm_year;
starttime[1] = localtime(&mystat[0].st_ctime);
if(starttime[1]->tm_year == year)
strftime(mod,13,"%b %e %R",starttime[1]);
else
strftime(mod,13,"%b %e %Y",starttime[1]);
printf(" \t%s",mod );
printf(" \t%ld",mystat[0].st_mtime);
printf(" \t%s\n",dient[0][count[4]]->d_name);
}
}
}
else {
if (count[2] == 1) {
printf(" %s\n",dient[0][count[4]]->d_name);
}
else {
if ((dient[0][count[4]] ->d_name)[0] != 46) printf("%s ",dient[0][count[4]]->d_name);
}
}
free(dient[0][count[4]]);
}
free(dient[0]);
}
return 1;
}
char* returnPath (char* cwd) {
int i,cwd_size = strlen(cwd), root_size = strlen(root);
if (root_size > cwd_size) {
return cwd;
}
else if (root_size == cwd_size) {
return "~";
}
else {
char *new = (char*)malloc(100);
new[0] = '~';
new[1] = '/';
for (i = 0 ; i < cwd_size-root_size-1; i++) {
new[i+2] = cwd[root_size+i+1];
}
return new;
}
}
void printPrompt (char *root) {
char hostname[1024];
char cwd[1024];
hostname[1023] = '\0';
gethostname(hostname, 1023);
char *username = getenv("USER");
getcwd(cwd, sizeof(cwd));
char *path = returnPath(cwd);
printf("\n<%s@%s:%s/> ",username, hostname, path);
}
char *readCommands (void) {
int buffer_size = 1024,check, pos = 0, i;
char *buffer = malloc(sizeof(char) * buffer_size);
if (!buffer) {
fprintf(stderr, "ALLOCATION ERROR\n");
exit(EXIT_FAILURE);
}
for (i = 0; ;i++) {
check = getchar();
if (check == EOF || check == '\n') {
buffer[pos] = '\0';
return buffer;
}
else
buffer[pos] = check;
pos++;
if (pos >= buffer_size) {
buffer_size += 1024;
buffer = realloc(buffer, buffer_size);
if (!buffer) {
fprintf(stderr, "ALLOCATION ERROR\n");
exit(EXIT_FAILURE);
}
}
}
}
char **splitLine (char* line) {
int buffer_size = COMM_BUFFER;
int position = 0, i = 0;
char **commands = malloc(buffer_size * (sizeof(char*)));
char *command;
if (!commands) {
fprintf(stderr, "Allocaiton Error \n");
exit(EXIT_FAILURE);
}
command = strtok(line, COMM_DELIM);
for (i = 0;; i++) {
if (command!= NULL) {
commands[position++] = command;
if (buffer_size < position) {
buffer_size += COMM_BUFFER;
commands = realloc(commands, buffer_size * sizeof(char*));
if (!commands) {
fprintf(stderr, "Allocaiton Error \n");
exit(EXIT_FAILURE);
}
}
command = strtok(NULL, COMM_DELIM);
continue;
}
break;
}
commands[position] = NULL;
return commands;
}
char **splitCommand (char* line) {
int buffer_size = TOK_BUFFER;
int position = 0, i = 0;
char **tokens = malloc(buffer_size * (sizeof(char*)));
char *token;
if (!tokens) {
fprintf(stderr, "Allocaiton Error \n");
exit(EXIT_FAILURE);
}
token = strtok(line, TOK_DELIM);
for (i = 0;; i++) {
if (token!= NULL) {
tokens[position++] = token;
if (buffer_size < position) {
buffer_size += TOK_BUFFER;
tokens = realloc(tokens, buffer_size * sizeof(char*));
if (!tokens) {
fprintf(stderr, "Allocaiton Error \n");
exit(EXIT_FAILURE);
}
}
token = strtok(NULL, TOK_DELIM);
continue;
}
break;
}
tokens[position] = NULL;
return tokens;
}
int launch (char** args) {
int i,j,background = 0, redirectflag = 0, piping = 0;
for (i = 0;args[i] != NULL;i++) {
for (j = 0;args[i][j] != '\0'; j++) {
if (args[i][j] == '>' || args[i][j] == '<') {
redirectflag = 1;
}
if (args[i][j] == '|') {
piping = 1;
}
if (args[i][j] == '&') {
background = 1;
}
}
}
if (piping) {
pipehandler(args);
return 1;
}
if (redirectflag) {
return redirect(args, i);
}
pid_t pid, wpid;
int state;
pid = fork();
if (pid < 0) {
perror("ERROR");
}
else if(!pid) {
if ( execvp(args[0], args) == -1)
perror("ERROR");
exit(EXIT_FAILURE);
}
if(!background) {
wpid = waitpid (pid, &state, WUNTRACED);
for (i = 0;; i++) {
if (!WIFEXITED(state) && !WIFSIGNALED(state)) {
wpid = waitpid (pid, &state, WUNTRACED);
continue;
}
break;
}
}
return 1;
}
int checkCommand (char** args) {
int count;
if (args[0] == NULL)
return EXIT_FAILURE;
count = 0;
while (count < sizeof(builtin_arr)/sizeof(char*)) {
if (strcmp(args[0],builtin_arr[count]) == 0)
return (*builtin_functions[count])(args);
count++;
}
return launch(args);
}
void interpretCommand(void) {
char **args;
char *commands;
char **split_line;
int state;
int i,j;
signal(SIGINT,sigintHandler);
for (i = 0;; i++) {
printPrompt(root);
commands = readCommands();
split_line = splitLine(commands);
for (j = 0;split_line[j] != NULL ;j++) {
args = splitCommand(split_line[j]);
state = checkCommand(args);
free (args);
if (!state) {
break;
}
}
free(commands);
free(split_line);
if(!state) {
break;
}
}
}
int main(int arg1, char **arg2) {
root = getenv("PWD");
interpretCommand();
return EXIT_SUCCESS;
}
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