Operating System Assignment 2
Operations on Processes -Simulation of Operating System Shell and its working
Practical Assignments:
Set A
Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. It accepts the command, tokenize the command line and execute it by creating the child process.Also implement the additional command ‘count’ as
myshell$ count c filename: It will display the number of characters in given file
myshell$ count w filename: It will display the number of words in given file
myshell$ count l filename: It will display the number of lines in given file
Program:-
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.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 count(char *fn, char op)
{
int fh,cc=0,wc=0,lc=0;
char c;
fh = open(fn,O_RDONLY);
if(fh==-1)
{
printf("File %s not found.\n",fn);
return;
}
while(read(fh,&c,1)>0)
{
if(c==' ') wc++;
else if(c=='\n')
{
wc++;
lc++;
}
cc++;
}
close(fh);
switch(op)
{
case 'c':
printf("No.of characters:%d\n",cc);
break;
case 'w':
printf("No.of words:%d\n",wc);
break;
case 'l':
printf("No.of lines:%d\n",lc);
break;
}
}
int main()
{
char buff[80],*args[10];
int pid;
while(1)
{
printf("myshell$");
fflush(stdin);
fgets(buff,80,stdin);
buff[strlen(buff)-1]='\0';
make_toks(buff,args);
if(strcmp(args[0],"count")==0)
count(args[2],args[1][0]);
else
{
pid = fork();
if(pid>0)
wait();
else
{
if(execvp(args[0],args)==-1)
printf("Bad command.\n");
}
}
}
return 0;
}
Set B
Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. 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.
Program :-
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.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("myshell$");
fflush(stdin);
fgets(buff,80,stdin);
buff[strlen(buff)-1]='\0';
make_toks(buff,args);
if(strcmp(args[0],"list")==0)
list(args[2],args[1][0]);
else
{
pid = fork();
if(pid>0)
wait();
else
{
if(execvp(args[0],args)==-1)
printf("Bad command.\n");
}
}
}
return 0;
}
Set C
(1)Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. It accepts the command, tokenize the command line and execute it by creating the child process. Also implement the additional command ‘typeline’ as
myshell$ typeline n filename: It will display first n lines of the file.
myshell$ typeline -n filename: It will display last n lines of the file.
myshell$ typeline a filename: It will display all the lines of the file.
Program:-
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.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 typeline(char *fn, char *op)
{
int fh,i,j,n;
char c;
fh = open(fn,O_RDONLY);
if(fh==-1)
{
printf("File %s not found.\n",fn);
return;
}
if(strcmp(op,"a")==0)
{
while(read(fh,&c,1)>0)
printf("%c",c);
close(fh);
return;
}
n = atoi(op);
if(n>0)
{
i=0;
while(read(fh,&c,1)>0)
{
printf("%c",c);
if(c=='\n') i++;
if(i==n) break;
}
}
if(n<0)
{
i=0;
while(read(fh,&c,1)>0)
{
if(c=='\n') i++;
}
lseek(fh,0,SEEK_SET);
j=0;
while(read(fh,&c,1)>0)
{
if(c=='\n') j++;
if(j==i+n) break;
}
while(read(fh,&c,1)>0)
{
printf("%c",c);
}
}
close(fh);
}
int main()
{
char buff[80],*args[10];
int pid;
while(1)
{
printf("myshell$");
fflush(stdin);
fgets(buff,80,stdin);
buff[strlen(buff)-1]='\0';
make_toks(buff,args);
if(strcmp(args[0],"typeline")==0)
typeline(args[2],args[1]);
else
{
pid = fork();
if(pid>0)
wait();
else
{
if(execvp(args[0],args)==-1)
printf("Bad command.\n");
}
}
}
return 0;
}
(2)Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. It accepts the command, tokenize the command line and execute it by creating the child process.Also implement the additional command ‘search’ as
myshell$ search f filename pattern : It will search the first occurrence of pattern in the given file
myshell$ search a filename pattern : It will search all the occurrence of pattern in the given file
myshell$ search c filename pattern : It will count the number of occurrence of pattern in the given file
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