**********************
Sample output: History
**********************

/home/cmpt300student$ ^C
/home/cmpt300student$ !!
SHELL: Unknown history command.
/home/cmpt300student$ !0
SHELL: Unknown history command.
/home/cmpt300student$ !1
SHELL: Unknown history command.
/home/cmpt300student$ ^C
/home/cmpt300student$ history
1	history
/home/cmpt300student$ ^C
1	history
/home/cmpt300student$ !!
history
1	history
2	history
/home/cmpt300student$ !1
history
1	history
2	history
3	history
/home/cmpt300student$ ls
gmon.out  shell    shell.o    shell_sol.c
Makefile  shell.c  shell_sol  shell_sol.o
/home/cmpt300student$ !!
ls
gmon.out  shell    shell.o    shell_sol.c
Makefile  shell.c  shell_sol  shell_sol.o
/home/cmpt300student$ ^C
1	history
2	history
3	history
4	ls
5	ls
/home/cmpt300student$ ls &
/home/cmpt300student$ gmon.out  shell    shell.o    shell_sol.c
Makefile  shell.c  shell_sol  shell_sol.o
  
/home/cmpt300student$ 
/home/cmpt300student$ 
/home/cmpt300student$ !!
ls &
/home/cmpt300student$ gmon.out  shell    shell.o    shell_sol.c
Makefile  shell.c  shell_sol  shell_sol.o

/home/cmpt300student$ 
/home/cmpt300student$ 
/home/cmpt300student$ ^C
1	history
2	history
3	history
4	ls
5	ls
6	ls &
7	ls &
/home/cmpt300student$ cat /proc/uptime
443532.91 1759811.59
/home/cmpt300student$ !!  
cat /proc/uptime
443539.61 1759830.53
/home/cmpt300student$ ^C
1	history
2	history
3	history
4	ls
5	ls
6	ls &
7	ls &
8	cat /proc/uptime
9	cat /proc/uptime
/home/cmpt300student$ cat /proc/version
Linux version 3.13.0-44-generic (buildd@lamiak) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) ) #73-Ubuntu SMP Tue Dec 16 00:22:43 UTC 2014
/home/cmpt300student$ ^C
1	history
2	history
3	history
4	ls
5	ls
6	ls &
7	ls &
8	cat /proc/uptime
9	cat /proc/uptime
10	cat /proc/version
/home/cmpt300student$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.13.0-44-generic root=UUID=37fc423b-ce79-4f9d-b149-59502584873d ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
/home/cmpt300student$ ^C
2	history
3	history
4	ls
5	ls
6	ls &
7	ls &
8	cat /proc/uptime
9	cat /proc/uptime
10	cat /proc/version
11	cat /proc/cmdline
/home/cmpt300student$ history
3	history
4	ls
5	ls
6	ls &
7	ls &
8	cat /proc/uptime
9	cat /proc/uptime
10	cat /proc/version
11	cat /proc/cmdline
12	history
/home/cmpt300student$ ^C
3	history
4	ls
5	ls
6	ls &
7	ls &
8	cat /proc/uptime
9	cat /proc/uptime
10	cat /proc/version
11	cat /proc/cmdline
12	history
/home/cmpt300student$ 
/home/cmpt300student$ 
/home/cmpt300student$ pwd
/home/cmpt300student
/home/cmpt300student$ cd /proc
/proc$ pwd
/proc
/proc$ ^C
6	ls &
7	ls &
8	cat /proc/uptime
9	cat /proc/uptime
10	cat /proc/version
11	cat /proc/cmdline
12	history
13	pwd
14	cd /proc
15	pwd
/proc$ cd /home/cmpt300student
/home/cmpt300student$ type ls
ls is external to shell300
ls is /bin/ls
/home/cmpt300student$ type cd
cd is a shell300 builtin
/home/cmpt300student$ type pwd
pwd is a shell300 builtin
/home/cmpt300student$ type exit
exit is a shell300 builtin