Exam Rank 04

Subject Text

Accepted file :

*.c , *.h

Allowed functions :

malloc, free, write, close, fork, waitpid, signal, kill, exit, chdir, execve, dup, dup2, pipe, strcmp, strncmp

The program :

Write a program that will behave like executing a shell command

The command line to execute will be the arguments of this program

Executable's path will be absolute or relative but your program must not build a path (from the PATH variable for example)

You must implement "|" and ";" like in bash

we will never try a "|" immediately followed or preceded by nothing or "|" or ";" Your program must implement the built-in command cd only with a path as argument (no '-' or without parameters)

if cd has the wrong number of argument your program should print in STDERR "error: cd: bad arguments" followed by a '\n' if cd failed your program should print in STDERR "error: cd: cannot change directory to path_to_change" followed by a '\n' with path_to_change replaced by the argument to cd a cd command will never be immediately followed or preceded by a "|" You don't need to manage any type of wildcards (*, ~ etc...)

You don't need to manage environment variables ($BLA ...)

If a system call, except execve and chdir, returns an error your program should immediatly print "error: fatal" in STDERR followed by a '\n' and the program should exit

If execve failed you should print "error: cannot execute executable_that_failed" in STDERR followed by a '\n' with executable_that_failed replaced with the path of the failed executable (It should be the first argument of execve)

Your program should be able to manage more than hundreds of "|" even if we limit the number of "open files" to less than 30.

Example :

$>./microshell /bin/ls "|" /usr/bin/grep microshell ";" /bin/echo i love my microshell
microshell
i love my microshell
$>