/4209-minishell

my daily digging on shell world

Primary LanguageC

minishell

This is a basic shell implementation called Minishell., made in C language It is a bash-like command-line interpreter which behaves as a basic bash environment. It supports various features such as command execution, input parsing, redirections, pipes, environment variables, built-in commands, and signal handling.

This project was developed in colaboration with fpinho-d.

Two Branchs

There are 2 branchs on this project. If you are starting your 'minishell' journey, the 'debug' branch is useful as it has debugging functionalities that you might find helpful to navigate the code while getting feedback about the where teh code goes and the variables and pointers values.

git clone 

git checkout debug

make

And you are ready to try it with some feedback about the program flow. If you want to get the feeling of it without any 'noise' then you shoul try the main branch version which is exactly like the debug version but withou any feedback besides the expected behaviour of a shell.

Words of Wisdom

Focus on the requirement 🎯

Please implement only what the subject explicitly requests. Anything that is not requested is not a requirement, and each additional implementation increases development time and adds unnecessary complexity to the project.

Perform extensive testing 🔬

This project has many points of attention that have arisen during development. All of these points have been included in the tests on this page. While not exhaustive, they provide a starting point for things that should work and things that should not. Check the tests

Study other shells 🔍

Our reference shell is Bash, but running certain commands in other shells may produce different results and help us better understand why certain things happen. Use Bash as a reference, but be open to examining the workings of other shells.

Features

  • Prompt display: Minishell displays a prompt when waiting for a new command.
  • Command history: It has a working history feature that allows navigating and reusing previous commands.
  • Command execution: Minishell can search and launch the appropriate executable based on the PATH variable or using a relative or absolute path.
  • Quoting: It handles single quotes ', preventing the interpretation of meta-characters within the quoted sequence. Double quotes " prevent the interpretation of meta-characters except for the dollar sign $.
  • Redirections: Minishell supports input <, output > and append output >> redirections. It also handles here documents << where input is read until a line containing the specified delimiter.
  • Pipes: It implements pipes | to connect the output of one command to the input of the next command in a pipeline.
  • Environment variables: Minishell handles the expansion of environment variables ($ followed by a sequence of characters) to their respective values.
  • Special variables: It supports the special variable $? which expands to the exit status of the most recently executed foreground pipeline.
  • Signal handling: Minishell handles signals such as ctrl-C (SIGINT), ctrl-D (EOF), and ctrl-\ (SIGQUIT) according to the specified behavior in the subject of this project.
  • Built-in commands: It provides several built-in commands, including echo, cd, pwd, export, unset, env, and exit, with their respective options and arguments.

Implementation Details

  • The shell uses the readline library to provide line editing capabilities and command history.
  • Input parsing is done using a combination of string manipulation and state tracking to handle quotes and command boundaries.
  • Command execution is managed through a commands_manager function that handles the execution of commands, including pipe setup and file descriptor management.
  • Built-in commands are implemented as separate functions and are executed within the shell process itself.
  • Error handling and reporting are done through a combination of error codes, error messages, and signal handling.

Usage

To compile the Minishell program, use the provided Makefile by running make in the project directory. This will generate an executable named minishell.

make

To run the Minishell program, simply execute the generated minishell binary.

./minishell

Once running, you can enter commands and interact with the shell.

Requirements

  • The Libft library is required and provided along with the project files.
  • The program was developed and tested on a Unix-based system. Compatibility with other platforms may vary.

Limitations

  • Minishell does not interpret unclosed quotes or special characters that are not required by the subject, such as backslashes \ or semicolons ;.
  • The readline() function used in Minishell may cause memory leaks, but the code written specifically for this project should not have memory leaks.

Minishell Tests

Check -Wall -Wextra -Werror

make -n

gcc -Wall -Wextra -Werror -c src/main.c -o obj/main.o

minishell instance

echo $MSHLVL

must dispaly the current minishell instance (when runing from bash it should be 1)

./minishell
echo $MSHLVL

must dispaly the current minishell instance (the previous instance should be previous instance + 1)

Some Simple Commands

/bin/ls

include libft Makefile minishell minishell_tester src

date

Wed 03 Mar 2024 1:43:66 WEST

ifconfig

network information

who

antoda-s- tty2 2024-03-13 21:53 (tty2)

[empty]

print a new line

[space]

print a new line

[tab]

do nothing

Command with Arguments

touch 1 2 3

create 3 files

/bin/ls -l

list files with details

rm 1 2 3

remove 3 files

cat Makefile

print the content of the Makefile

cat -e Makefile

print the content of the Makefile with $ at the end of each line

wc -l Makefile

55 Makefile

echo

echo

print a new line

echo This is a test

This is a test

echo -n Hello World

Hello World/home/antoda-s-$

exit

exit

exit the minishell

exit 1

exit the minishell with return code 1

exit 42

exit the minishell with return code 42

exit -42

exit the minishell with return code 214

exit 42 10

minishell: exit: too many arguments

exit 42scholl

minishell: exit: numeric argument required; then exit with error code 2

Return value of a process

echo $?

0

/bin/ls

then run echo $?; the return code is 0

ls notexist

then run echo $?; the return code is 2

/bin/notexist

then run echo $?; the return code is 127

expr $? + $?

then run echo $?; the return code is 2

Signals

ctrl-C on empty prompt

display a new line with a new prompt
echo $? must display 130

ctrl-\ on empty prompt

do nothing

ctrl-D on empty prompt

quit minishell
echo $? must display 0

ctrl-C after write some stuff

display a new line with a new prompt
echo $? must display 130

ctrl-\ after write some stuff

do nothing

ctrl-D after write some stuff

do nothing

ctrl-C in cat without arguments

^C
echo $? must display 130

ctrl-\ in cat without arguments

\Quit (core dumped)
echo $? must display 131

ctrl-D in cat without arguments

close interactive mode
echo $? must display 0

Double Quotes

"/bin/ls"

execute ls

""ls""

execute ls

""ls -l""

execute ls with details

"""ls -l"""

minishell: ls -l: command not found

"echo Hello World"

minishell: echo Hello World: command not found

echo "Hello World"

Hello World

echo "with       spaces"

Hello World

echo "test with %specials *chars"

test with %specials *chars

echo "cat lol.c cat > Iol.c"

cat lol.c cat > Iol.c

echo "

minishell: unclosed quotes

Single Quotes

'/bin/ls'

execute ls

''ls''

execute ls

''ls -l''

execute ls with details

'''ls -l'''

minishell: ls -l: command not found

'echo Hello World'

minishell: echo Hello World: command not found

echo 'Hello World'

Hello World

echo 'with       spaces'

Hello World

echo '$USER'

$USER

echo '

minishell: unclosed quotes

echo '$HOME > home.txt'

$HOME > home.txt

echo '$?'

$?

env

env

print the environment variables

env PATH

minishell: env: Arguments and options aren't supported

export

export

print the exported environment variables

export NEW_VAR=42

add NEW_VAR with content 42

export NEW_VAR="A little change"

replace the value of NEW_VAR

export NEW_VAR=

replace the content of NEW_VAR to empty

export NEW_VAR=$USER

replace the value of NEW_VAR

export NEW_VAR="with unclosed quotes

minishell: unclosed quotes

export -p NEW_VAR

minishell: export: options aren't supported

export NEW_VAR="   -l  |"

replace the content of NEW_VAR to ' -l |'

unset

unset NEW_VAR

remove the environment variable

unset -n NEW_VAR

minishell: unset: options aren't supported

cd

cd .

stay in the same directory

cd . ls

minishell: cd: too many arguments

cd ..

go to the parent directory

cd /usr/bin

go to the /usr/bin directory

cd

go to the home directory

cd notexist

minishell: cd: notexist: No such file or directory

pwd

pwd

/home/antoda-s-/workplace/common_core/minishell/minishell

pwd -L

minishell: pwd: options aren't supported

Relative Path

./minishell

execute the minishell inside minishell

../../../../../../bin/ls

include libft Makefile minishell minishell_tester src

Environment path

echo $PATH

/home/antoda-s-/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/bin

unset PATH

remove the PATH environment variable

ls

minishell: ls: command not found

export PATH=/bin:/usr/bin

set the PATH environment variable with the basic path again

Redirection

ls -l > test

create a file with the files list inside

cat Makefile >> test

append the content of the Makefile to the file

wc -l < test

63

wc -c < test > test_out

test_out receive the number of characters in the file test

cat << EOF

start the here document

cat << EOF | wc -l

print the number of lines in the here document

Pipes

cat Makefile | grep NAME | wc -l

5

cat notexist | wc -l

cat: notexist: No such file or directory 0

< Makefile grep NAME | wc -l > out

put the result in out

Go Crazy and history

up down to navigate in the history

 dsfdfdfd

minishell: command not found

wc -l < /etc/passwd > file1 > file2 > file3 > file4

write the result in the last redirection

cat | cat | ls

print list files and open the interactive mode

Environment variables

echo $USER

antoda-s-

echo $notexist

print an empty line

echo "$HOME"

/home/antoda-s-

echo ~

/home/antoda-s-

echo ~test

~test

echo test~

test~

echo ~/test

/home/antoda-s-/test

Trouble Cases

$EMPTYVAR

show a new prompt line

echo -n -n -n -n -n Hello World

Hello World/home/antoda-s-$

echo -nnnnnnnnn Hello World

Hello World/home/antoda-s-$

echo $HOME.test

/home/antoda-s-.test

echo $HOME/test

/home/antoda-s-/test

;

minishell: no support for operator `;'

*

minishell: no support for operator `*'

>

minishell: syntax error near unexpected token `newline'

<

minishell: syntax error near unexpected token `newline'

< .

minishell: syntax error near unexpected token `newline'

>>

minishell: syntax error near unexpected token `newline'

<<

minishell: syntax error near unexpected token `newline'

|

minishell: syntax error near unexpected token `|'

d|

minishell: no support for pipe prompt

ls | wc |

minishell: no support for pipe prompt

ls | wc >

minishell: syntax error near unexpected token `newline'

ls | wc <

minishell: syntax error near unexpected token `newline'

ls | wc <<

minishell: syntax error near unexpected token `newline'

ls | wc >>

minishell: syntax error near unexpected token `newline'

ls | cat << > | wc

minishell: syntax error near unexpected token `<< '

export =

minishell: export: `=': not a valid identifier

export =test

minishell: export: `=test': not a valid identifier

export TEST.=test

minishell: export: `TEST.=test': not a valid identifier

export 1TEST=test

minishell: export: `1TEST=test': not a valid identifier

export TEST=ABCD

create a var TEST with content ABCD

export $TEST=1234

create a var ABCD with content 1234

export $ABCD=more

minishell: export: `1234=more': not a valid identifier

export a_test b_test

create tmp vars without content

unset a_test

remove the tmp var a_test

export b_test=1234

transform the tmp var b_test in a environment var with content 1234

unset b_test

remove the environment var b_test

export TEST1="withdouble" TEST2 TEST3=wihoutquotes TEST4="with spaces and expand $USER" TEST5="ok, but it has more" TEST6= TEST7='with single $PATH' = TEST8 9TEST9 TEST10="" TEST11=too=many=equals TEST.12="    " TEST13='withsingle' TEST14/

This test will try to create environment vars and tmp vars with different cases. Check the difference with env and export commands

unset TEST1 TEST2 TEST3 TEST4 TEST5 TEST6 TEST7 TEST8 9TEST9 TEST10 TEST11 TEST.12 TEST13 TEST14/

unset all these variables that were valid

Not required but done

cd -

go to the previous directory

<< EOF

start the here document

> file

create a file

>> file

append to a file

Grade: 112/100

Used tests