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https://github.com/bshongwe/simple_shell

ALX Team Project
https://github.com/bshongwe/simple_shell

c-language-programming unix-shell

Last synced: 9 months ago
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ALX Team Project

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README 

          
# 0x16. C - Simple Shell



## General



-  Who designed and implemented the original Unix operating system

-  Who wrote the first version of the UNIX shell

-  Who invented the B programming language (the direct predecessor to the C programming language)

-  Who is Ken Thompson

-  How does a shell work

-  What is a pid and a ppid

-  How to manipulate the environment of the current process

-  What is the difference between a function and a system call

-  How to create processes

-  What are the three prototypes of main

-  How does the shell use the PATH to find the programs

-  How to execute another program with the execve system call

-  How to suspend the execution of a process until one of its children terminates

-  What is EOF / “end-of-file”?

-  All your files should end with a new line

-  A README.md file, at the root of the folder of the project is mandatory

-  Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl

-  Your shell should not have any memory leaks

-  No more than 5 functions per file

-  All your header files should be include guarded

-  Use system calls only when you need to (why?)

-  Write a README with the description of your project

-  You should have an AUTHORS file at the root of your repository, listing all individuals having contributed content to the repository. Format, see Docker



## GitHub



*There should be one project repository per group. If you and your partner have a repository with the same name in both your accounts, you risk a 0% score. Add your partner as a collaborator. *



## Output



Unless specified otherwise, your 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 your argv[0]



## List of allowed functions and system calls



-  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)

-  getpid (man 2 getpid)

-  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)



## Compilation



Your shell will be compiled this way: gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh



## Testing



Your shell should work like this in interactive mode:



    $ ./hsh

    ($) /bin/ls

    hsh main.c shell.c

    ($)

    ($) exit

    $



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

    $



## Checks

We strongly encourage the entire class to work together to create a suite of checks covering both regular tests and edge cases for each task. See task 8. Test suite.



GitHub repository: simple_shell



## Tasks

### Task 0. Betty would be proud



Write a beautiful code that passes the Betty checks



### Task 1. Simple shell 0.1



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…



    

### Task 2. Simple shell 0.2



Simple shell 0.1 +

Handle command lines with arguments



### Task 3. Simple shell 0.3



Simple shell 0.2 +

Handle the PATH

-  fork must not be called if the command doesn’t exist



    

### Task 4. Simple shell 0.4



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



    

### Task 5. Simple shell 1.0



Simple shell 0.4 +

Implement the env built-in, that prints the current environment



### Task 6. Simple shell 0.1.1



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



    

### Task 7. Simple shell 0.2.1



Simple shell 0.2 +

You are not allowed to use strtok



    

### Task 8. Simple shell 0.4.1



Simple shell 0.4 +

handle arguments for the built-in exit



Usage: exit status, where status is an integer used to exit the shell



    

### Task 9. setenv, unsetenv



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



    

### Task 10. cd



Simple shell 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



### Task 11. ;



Simple shell 1.0 +

Handle the commands separator ;



### Task 12. && and ||



Simple shell 1.0 +

Handle the && and || shell logical operators



### Task 13. alias



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



### Task 14. Variables



Simple shell 1.0 +

-  Handle variables replacement

-  Handle the $? variable

-  Handle the $$ variable



### Task 15. Comments



Simple shell 1.0 +

Handle comments (#)



    

### Task 16. File as input



Simple shell 1.0 +



Usage: simple_shell [filename]



-  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



Authors: Ernest Bhekizwe Shongwe, Garrick Larson Potts. (Credit to my Printf patner, Zikona  Mnyaka, for bringing this project ack to life)