- Write a simple UNIX command interpreter.
What we should learn from this project:
- 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 files will be compiled on Ubuntu 14.04 LTS
- Our shell will be compiled with gcc 4.8.4 using the flags -Wall -Werror -Wextra and -pedantic
- README is present
- A man for your shell.
- AUTHORS file at the root of your repository, listing all individuals having contributed content to the repository.
- Code is compliant to Betty style format
- Contribute to a test suite for your shell.
A UNIX command line interpreter.
- The 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.
- Handles the “end of file” condition (Ctrl+D)
It does not:
- use the PATH
- implement built-ins
- handle special characters : ", ', `, , *, &, #
- be able to move the cursor
- handle commands with arguments
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$ ./shelly
$ /bin/ls
atoi.c getenv.c _memcpy.c _strlen.c
AUTHORS getenviron.c printenv.c _strncmp.c
builtin.h get_global.c README.md _strncpy.c
_cd.c _getline.c _realloc.c _strndup.c
environment.h get_nargs.c shelly _strtok.c
exit_.c getpath.c stdlibwrapper.h _strtoll.c
free_linkedlist.c global.h _strcat.c strtow.c
frees.c inputhelper.h _strcmp.c which.c
get_builtin_func.c linkedlist.h _strcpy.c
get_builtin_ld.c main.c _strdup.c
get_builtin_sd.c man_1_simple_shell stringwrapper.h
Simple shell 0.1
- Our own getline function
- Use a buffer to read many chars at once and call the least possible the read system call
- We do not use getline
It does not:
- move the cursor
Simple shell 0.1
- Handle command lines with arguments
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$ ./shelly
$ ls -la
total 240
drwxrwxr-x 3 vagrant vagrant 4096 Aug 18 06:57 .
drwxr-xr-x 23 vagrant vagrant 4096 Aug 18 06:07 ..
-rw-rw-r-- 1 vagrant vagrant 768 Aug 17 20:45 atoi.c
-rw-rw-r-- 1 vagrant vagrant 135 Aug 18 02:53 AUTHORS
-rw-rw-r-- 1 vagrant vagrant 660 Aug 17 22:18 builtin.h
-rw-rw-r-- 1 vagrant vagrant 621 Aug 17 22:18 _cd.c
-rw-rw-r-- 1 vagrant vagrant 345 Aug 17 22:18 environment.h
-rw-rw-r-- 1 vagrant vagrant 411 Aug 17 22:18 exit_.c
-rw-rw-r-- 1 vagrant vagrant 196 Aug 17 22:18 free_linkedlist.c
-rw-rw-r-- 1 vagrant vagrant 161 Aug 17 22:18 frees.c
-rw-rw-r-- 1 vagrant vagrant 519 Aug 17 20:45 get_builtin_func.c
-rw-rw-r-- 1 vagrant vagrant 525 Aug 17 09:01 get_builtin_ld.c
-rw-rw-r-- 1 vagrant vagrant 604 Aug 17 22:04 get_builtin_sd.c
-rw-rw-r-- 1 vagrant vagrant 390 Aug 17 22:18 getenv.c
-rw-rw-r-- 1 vagrant vagrant 1140 Aug 17 22:18 getenviron.c
-rw-rw-r-- 1 vagrant vagrant 143 Aug 17 22:18 get_global.c
-rw-rw-r-- 1 vagrant vagrant 746 Aug 17 22:18 _getline.c
-rw-rw-r-- 1 vagrant vagrant 378 Aug 17 22:18 get_nargs.c
-rw-rw-r-- 1 vagrant vagrant 568 Aug 17 19:18 getpath.c
drwxrwxr-x 8 vagrant vagrant 4096 Aug 18 02:55 .git
-rw-rw-r-- 1 vagrant vagrant 15 Aug 17 01:01 .gitignore
-rw-rw-r-- 1 vagrant vagrant 167 Aug 17 22:18 global.h
-rw-rw-r-- 1 vagrant vagrant 146 Aug 17 19:18 inputhelper.h
-rw-rw-r-- 1 vagrant vagrant 411 Aug 17 22:18 linkedlist.h
-rw-rw-r-- 1 vagrant vagrant 2002 Aug 17 22:39 main.c
-rwxrw-r-- 1 vagrant vagrant 1618 Aug 18 02:52 man_1_simple_shell
-rw-rw-r-- 1 vagrant vagrant 337 Aug 17 19:18 _memcpy.c
-rw-rw-r-- 1 vagrant vagrant 339 Aug 17 22:39 printenv.c
-rw-rw-r-- 1 vagrant vagrant 2162 Aug 18 06:07 README.md
-rw-r--r-- 1 vagrant vagrant 20480 Aug 18 07:10 .README.md.swp
-rw-rw-r-- 1 vagrant vagrant 581 Aug 17 22:18 _realloc.c
-rwxrwxr-x 1 vagrant vagrant 42459 Aug 18 06:57 shelly
-rw-rw-r-- 1 vagrant vagrant 245 Aug 17 19:18 stdlibwrapper.h
-rw-rw-r-- 1 vagrant vagrant 421 Aug 17 19:18 _strcat.c
-rw-rw-r-- 1 vagrant vagrant 319 Aug 17 19:18 _strcmp.c
-rw-rw-r-- 1 vagrant vagrant 403 Aug 17 19:18 _strcpy.c
-rw-rw-r-- 1 vagrant vagrant 592 Aug 17 19:35 _strdup.c
-rw-rw-r-- 1 vagrant vagrant 611 Aug 17 22:39 stringwrapper.h
-rw-rw-r-- 1 vagrant vagrant 236 Aug 17 19:18 _strlen.c
-rw-rw-r-- 1 vagrant vagrant 303 Aug 17 22:18 _strncmp.c
-rw-rw-r-- 1 vagrant vagrant 441 Aug 17 21:06 _strncpy.c
-rw-rw-r-- 1 vagrant vagrant 634 Aug 17 19:35 _strndup.c
-rw-rw-r-- 1 vagrant vagrant 105 Aug 17 22:18 _strtok.c
-rw-rw-r-- 1 vagrant vagrant 1056 Aug 17 19:18 _strtoll.c
-rw-rw-r-- 1 vagrant vagrant 506 Aug 17 22:18 strtow.c
-rw-rw-r-- 1 vagrant vagrant 807 Aug 17 22:18 which.c
Simple shell 0.2
- Our own strtok
Simple shell 0.2
- Handle the PATH
Simple shell 0.3
- Implement the exit built-in, that exits the shell
- Usage: exit
- No arguments to the built-in exit
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$ ./shelly
$ exit
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$
Simple shell 0.4
- handle arguments for the built-in exit
- Usage: exit status, where status is an integer used to exit the shell
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$ ./shelly
$ exit 98
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$ echo $?
98
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$
Simple shell 0.4
- Handle Ctrl+C: your shell should not quit when the user inputs ^C
Simple shell 0.4
- Implement the env built-in, that prints the current environment
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$ ./shelly
$ env
XDG_SESSION_ID=2
TERM=xterm-256color
SHELL=/bin/bash
SSH_CLIENT=10.0.2.2 49536 22
OLDPWD=/home/vagrant
SSH_TTY=/dev/pts/0
USER=vagrant
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lz=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.axa=00;36:*.oga=00;36:*.spx=00;36:*.xspf=00;36:
MAIL=/var/mail/vagrant
PATH=/home/vagrant/bin
PWD=/home/vagrant/simple_shell
LANG=en_US.UTF-8
SHLVL=1
HOME=/home/vagrant
LC_TERMINAL_VERSION=3.3.1
LOGNAME=vagrant
SSH_CONNECTION=10.0.2.2 49536 10.0.2.15 22
LC_CTYPE=en_US.UTF-8
LESSOPEN=| /usr/bin/lesspipe %s
XDG_RUNTIME_DIR=/run/user/1000
LC_TERMINAL=iTerm2
LESSCLOSE=/usr/bin/lesspipe %s %s
_=./shelly
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 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
Simple shell 1.0
- Implement the help built-in
- Usage: help [BUILTIN]
- Ben Cook - benjamesian
- Ryuichi Miyazaki - rmiyazaki6499