OS-(I) Assignment 2: Set B- 1)

Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. It accepts the command, tokenize the command line and execute it by creating the child process.
Also implement the additional command ‘list’ as
myshell$ list f dirname: It will display filenames in a given directory.
myshell$ list n dirname: It will count the number of entries in a given directory.
myshell$ list i dirname: It will display filenames and their inode number for the files in a given directory.

Solution:

#include <stdio.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <stdlib.h>

#include <string.h>

#include <dirent.h>

void make_toks(char *s, char *tok[])

{

int i=0;

char *p;

p = strtok(s," ");

while(p!=NULL)

{

tok[i++]=p;

p=strtok(NULL," ");

}

tok[i]=NULL;

}

void list(char *dn, char op)

{

DIR *dp;

struct dirent *entry;

int dc=0,fc=0;

dp = opendir(dn);

if(dp==NULL)

{

printf("Dir %s not found.\n",dn);

return;

}

switch(op)

{

case 'f':

while(entry=readdir(dp))

{

if(entry->d_type==DT_REG)

printf("%s\n",entry->d_name);

}

break;

case 'n':

while(entry=readdir(dp))

{

if(entry->d_type==DT_DIR)

dc++;

if(entry->d_type==DT_REG)

fc++;

}

printf("%d Dir(s)\t%d File(s)\n",dc,fc);

break;

case 'i':

while(entry=readdir(dp))

{

if(entry->d_type==DT_REG)

         printf("%s\t%d\n",entry->d_name,entry->d_fileno);

}

}

closedir(dp);

}

int main()

{

char buff[80],*args[10];

int pid;

while(1)

{

printf("\nmyshell$");

fflush(stdin);

fgets(buff,80,stdin);

buff[strlen(buff)-1]='\0';

make_toks(buff,args);

if(strcmp(args[0],"list")==0)

list(args[2],args[1][0]);

else

{

pid = fork();

if(pid>0)

wait();

else

{

if(execvp(args[0],args)==-1)

printf("Bad command.\n");

}

}

}