Question

You are required to develop a simple Linux shell in C language “shell.c".

The shell has to perform the following requirements: - - The shell prompt is “"myshell>".

- Run commands either from current directory or from “/bin" directory using the "exec" system call.

- Support output redirection like "command> filename" using "dup" system call. Note: save the output of the comment in the (filename).

- Implement the “history shell command to list the last ten commands entered so far.

- Implement the "clear" shell command to empty the history commands.

PLEASE Make sure you handle all cases, exceptions and cover possible user mistakes with clear and proper messages.

You are required to develop a simple Linux shell in C language "shell.c". The shell has to perform the following requirements: - The shell prompt is “myshell>". - Run commands either from current directory or from “/bin" directory using the "exec" system call. - Support output redirection like "command> filename" using "dup" system call. Note: save the output of the comment in the (filename). Implement the "history shell command to list the last ten commands entered so far. Implement the "clear" shell command to empty the history commands. PLEASE Make sure you handle all cases, exceptions and cover possible user mistakes with clear and proper messages.

Answer 1

MYSHELL:

=======================================================================

#include<stdio.h>

#include<unistd.h>

#include<string.h>

int main()

{

char command[20]; //storing the input

while(1){

printf("myshell>");

scanf("%s",command);

if(strcmp(command,"history")==0) //HISTORY

{

char *tailPath="/usr/bin/tail";   //tail path

char *cmd="tail";   //tail is the command

char *filename="/home/Myshell/.bash_history"; //history is stored in .bash history file of a user's home directory

execlp(tailPath,cmd,filename,NULL);   //call execlp

}

else if(strcmp(command,"clear")==0)   //CLEAR

{

char *rmPath="/bin/rm"; //we can delete history file using rm command

char *cmd="rm";

char *filename="/home/Myshell/.bash_history";

execlp(rmPath,cmd,filename,NULL);

}

else

{

printf("Invalid command\n");

}

}

return 0;

}