This is a simple implementation of a UNIX command line interpreter. The shell can interpret and execute command line arguments read from the standard input. the shell read lines from a file or terminal line which is then interpreted and executed if the command is valid
All the files are to be compiled on an Ubuntu 14.04 LTS machine with: gcc -Wall -Werror -Wextra -pedantic *.c All files ends end with a new line, with no memory leaks All code will use the Betty style. It will be checked using betty-style.pl and betty-doc.pl All code will be tested using the test files in the test folder. The simple shell supports most shell commands, such as cat, pwd, ls -la and more. Return Value : The shell returns a value of 0 if the command is valid and the command is executed successfully.
The program must have the exact same output as sh (/bin/sh) as well as the exact same error output. The only difference is when you print an error, the name of the program must be equivalent to the argv[0] Usage
- access (man 2 access)
- chdir (man 2 chdir)
- close (man 2 close)
- closedir (man 3 closedir)
- execve (man 2 execve)
- exit (man 3 exit)
- _exit (man 2 _exit)
- fflush (man 3 fflush)
- fork (man 2 fork)
- free (man 3 free)
- getcwd (man 3 getcwd)
- getline (man 3 getline)
- isatty (man 3 isatty)
- kill (man 2 kill)
- malloc (man 3 malloc)
- open (man 2 open)
- opendir (man 3 opendir)
- perror (man 3 perror)
- read (man 2 read)
- readdir (man 3 readdir)
- signal (man 2 signal)
- stat (__xstat) (man 2 stat)
- lstat (__lxstat) (man 2 lstat)
- fstat (__fxstat) (man 2 fstat)
- strtok (man 3 strtok)
- wait (man 2 wait)
- waitpid (man 2 waitpid)
- wait3 (man 2 wait3)
- wait4 (man 2 wait4)
- write (man 2 write)
The shell will be compiled this way: gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh
The shell works like this in interactive mode:
$ ./hsh
(
But also in non-interactive mode:
$ echo "/bin/ls" | ./hsh hsh main.c shell.c test_ls_2 $ $ cat test_ls_2 /bin/ls /bin/ls $ $ cat test_ls_2 | ./hsh hsh main.c shell.c test_ls_2 hsh main.c shell.c test_ls_2 $
Write a beautiful code that passes the Betty checks
Write a UNIX command line interpreter.
Usage: simple_shell Your Shell should:
Display a prompt and wait for the user to type a command. A command line always ends with a new line. The prompt is displayed again each time a command has been executed. The command lines are simple, no semicolons, no pipes, no redirections or any other advanced features. The command lines are made only of one word. No arguments will be passed to programs. If an executable cannot be found, print an error message and display the prompt again. Handle errors. You have to handle the “end of file” condition (Ctrl+D) You don’t have to:
use the PATH implement built-ins handle special characters : ", ', `, , *, &, # be able to move the cursor handle commands with arguments execve will be the core part of your Shell, don’t forget to pass the environ to it…
Simple shell 0.2 +
Handle the PATH fork must not be called if the command doesn’t exist
Simple shell 0.3 +
Implement the exit built-in, that exits the shell Usage: exit You don’t have to handle any argument to the built-in exit
Simple shell 0.4 +
Implement the env built-in, that prints the current environment
end of mandatory
Advanced Tasks
Simple shell 0.1 +
Write your own getline function Use a buffer to read many chars at once and call the least possible the read system call You will need to use static variables You are not allowed to use getline You don't have to:
be able to move the cursor
Simple shell 0.2 +
You are not allowed to use strtok
Simple shell 0.4 +
handles arguments for a built-in exit
Usage: exit status, where status is an integer used to exit the shell
julien@ubuntu:/shell$ ./shell_0.4.1
$ exit 98
julien@ubuntu:/shell$ echo
Simple shell 1.0 +
Implement the setenv and unsetenv builtin commands
setenv initialize a new environment variable, or modify an existing one Command syntax: setenv VARIABLE VALUE Should print something on stderr on failure unsetenv Remove an environment variable Command syntax: unsetenv VARIABLE Should print something on stderr on failure
Simple sell 1.0 +
Implement the builtin command cd:
Changes the current directory of the process Command syntax: cd [DIRECTORY] If no argument is given to cd the command must be interpreted like cd $HOME You have to handle the command cd - You have to update the environment variable PWD when you change directory man chdir, man getcwd
Simple shell 1.0 +
Handle the commands separator ;
alex@$ ls /var ; ls /var
backups cache crash lib local lock log mail metrics opt run spool tmp
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@$ ls /hbtn ; ls /var
ls: cannot access /hbtn: No such file or directory
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@$ ls /var ; ls /hbtn
backups cache crash lib local lock log mail metrics opt run spool tmp
ls: cannot access /hbtn: No such file or directory
alex@$ ls /var ; ls /hbtn ; ls /var ; ls /var
backups cache crash lib local lock log mail metrics opt run spool tmp
ls: cannot access /hbtn: No such file or directory
backups cache crash lib local lock log mail metrics opt run spool tmp
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@~$
Simple shell 1.0 +
Handle the && and || shell logical operators
alex@$ ls /var && ls /var
backups cache crash lib local lock log mail metrics opt run spool tmp
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@$ ls /hbtn && ls /var
ls: cannot access /hbtn: No such file or directory
alex@$ ls /var && ls /var && ls /var && ls /hbtn
backups cache crash lib local lock log mail metrics opt run spool tmp
backups cache crash lib local lock log mail metrics opt run spool tmp
backups cache crash lib local lock log mail metrics opt run spool tmp
ls: cannot access /hbtn: No such file or directory
alex@$ ls /var && ls /var && ls /var && ls /hbtn && ls /hbtn
backups cache crash lib local lock log mail metrics opt run spool tmp
backups cache crash lib local lock log mail metrics opt run spool tmp
backups cache crash lib local lock log mail metrics opt run spool tmp
ls: cannot access /hbtn: No such file or directory
alex@$
alex@$ ls /var || ls /var
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@$ ls /hbtn || ls /var
ls: cannot access /hbtn: No such file or directory
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@$ ls /hbtn || ls /hbtn || ls /hbtn || ls /var
ls: cannot access /hbtn: No such file or directory
ls: cannot access /hbtn: No such file or directory
ls: cannot access /hbtn: No such file or directory
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@$ ls /hbtn || ls /hbtn || ls /hbtn || ls /var || ls /var
ls: cannot access /hbtn: No such file or directory
ls: cannot access /hbtn: No such file or directory
ls: cannot access /hbtn: No such file or directory
backups cache crash lib local lock log mail metrics opt run spool tmp
alex@$
Simple shell 1.0 +
Implement the alias builtin command Usage: alias [name[='value'] ...] alias: Prints a list of all aliases, one per line, in the form name='value' alias name [name2 ...]: Prints the aliases name, name2, etc 1 per line, in the form name='value' alias name='value' [...]: Defines an alias for each name whose value is given. If name is already an alias, replaces its value with value
Simple shell 1.0 +
Handle variables replacement
Handle the /shell$ ./hsh
$ ls /var
backups cache crash lib local lock log mail metrics opt run snap spool tmp
$ echo /shell$
Simple shell 1.0 +
Handle comments (#)
julien@ubuntu:/shell$ sh
$ echo $$ # ls -la
5114
$ exit
julien@ubuntu:/shell$
Simple shell 1.0 +
Your shell can take a file as a command line argument The file contains all the commands that your shell should run before exiting The file should contain one command per line In this mode, the shell should not print a prompt and should not read from stdin
Kevin Odo
Abdulrahaman Abdulrahaman