MTech Advanced Operating Systems Lab (14SCS16)(1st sem)
Design and Develop a shell that should support at
least 20 commands.
#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<unistd.h>
void
parse(char *cmd, char **arguvec)
{
while(*cmd != '\0')
{
while( *cmd == ' ' || *cmd == '\t' || *cmd == '\n')
*cmd++='\0';
*arguvec++=cmd;
while(*cmd != '\0'
&& *cmd != ' ' && *cmd !=
'\t' && *cmd != '\n')
cmd++;
}
*arguvec = '\0';
}
void
cmdexecutes(char **arguvec)
{
pid_t pid;
int status;
pid = fork();
if(pid < 0)
{
printf("\n error in
creating fork");
exit(0);
}
else if(pid == 0)
{
if(execvp (*arguvec, arguvec)
< 0)
{
printf("\n
error in calling exec");
exit(0);
}
}
else
{
while(wait(&status) !=
pid);
}
}
int
main()
{
char cmd[1024];
char *arguvec[20];
while(1)
{
printf("[MYSHELL]");
gets(cmd);
parse(cmd, arguvec);
if( strcmp(arguvec[0], "exit")
== 0)
{
exit(0);
}
cmdexecutes(arguvec);
}
return 0;
}
Output:
ubuntu@ubuntu-VirtualBox:~/lab$
gedit 1.c
ubuntu@ubuntu-VirtualBox:~/lab$
cc 1.c
ubuntu@ubuntu-VirtualBox:~/lab$
./a.out
[MYSHELL]ls
1.c 1.c~
a.out
[MYSHELL]who
ubuntu tty7
2015-11-25 09:04
ubuntu pts/1
2015-11-25 09:27 (:0)
[MYSHELL]ps
PID TTY TIME CMD
2610 pts/1 00:00:01
bash
2825 pts/1 00:00:00
a.out
2828 pts/1 00:00:00
ps
[MYSHELL]date
Wed
Nov 25 09:38:46 IST 2015
[MYSHELL]cal
November 2015
Su
Mo Tu We Th Fr Sa
1
2 3 4
5 6 7
8 9 10
11 12 13 14
15
16 17 18 19 20 21
22
23 24 25 26 27 28
29
30
[MYSHELL]pwd
/home/ubuntu/lab
[MYSHELL]
