minishell

About the project

This project is about creating a simple shell. Yes, the own little bash :)

The program is capable of parsing a prompt and launching executables with arguments, along with its own 7 built-in functions.

As the project name implies, this is a mandatory-parted project - therefore it does not contain a bonus part.

So many wildcards and special characters, like ';' or '' are not supported.

This minishell is able to interpret the following elements:

1. a working history is setup and updates after every input. Delimiter is seen. However, it doesn’t have to update the history!

2. single quotes are handled, which should prevent the shell from interpreting the metacharacters in the quoted sequence.

3. double quotes are handled, which should prevent the shell from interpreting the metacharacters in the quoted sequence except for $ (dollar sign).

4. redirections:

   (<) - should redirect input.

   (>)- should redirect output.

   (<<) - should be given a delimiter, then read the input until a line containing the

   (>>) - should redirect output in append mode.

5. pipes are implemented (| character). The output of each command in the pipeline is connected to the input of the next command via a pipe.

6. environment variables are handled ($ followed by a sequence of characters) which should expand to their values.

7. $? is handled which should expand to the exit status of the most recently executed foreground pipeline.

8. ctrl-C, and ctrl-\ signals as well as ctrl-D key input are handled, which should behave like in bash.

9. In interactive mode:

   ctrl-C displays a new prompt on a new line.

   ctrl-D exits the shell.

   ctrl-\ does nothing.

10. builtins: echo with option -n

    cd with only a relative or absolute path

    pwd with no options

    export with no options

    unset with no options

    env with no options or arguments

    exit with no options

Getting started

If you have things setup different you can find the path to readline with this:

`brew --prefix readline`

Check if readline is installed with this:

`brew info readline`

Install with:

`brew install readline`

Usage

make

./minishell

Edge cases for testing purposes

cd

cd
cd ..
cd
cd ..
cd .
cd /Users
cd //
cd '//'
cd //////
cd ./././
cd '/etc'
cd '/var'
cd "$PWD/prompt"
cd "doesntexist"
cd "doesntexist" 2>/dev/null
cd ../../..
cd ?
cd '/'
cd $PWD/file_tests
cd $OLDPWD/builtins
cd .. | echo "something"
cd / | echo "something"
cd .. | pwd

echo

echo $ $
ECHO
echo rhobebou
echo "bonjour"
echo -n bonjour
echo -nn bonjour
echo -n -n -n bonjour
echo "-n" bonjour
echo text"$USER"
echo text"'$USER'" ' $USER '
echo "text"   "$USER"    "$USER"
echo               text "$USER"            "$USER"text
echo ''''''''''$USER''''''''''
echo """"""""$USER""""""""
echo $USER'$USER'text oui oui     oui  oui $USER oui      $USER '
echo "$USER""$USER""$USER"
echo text"$USER"test
echo '$USER' "$USER" "text \' text"
echo '$USER'
echo $USER " "
echo "$USER""Users/$USER/file""'$USER'"'$USER'
echo "$USER$USER$USER"
echo '$USER'"$USER"'$USER'
echo '"$USER"''$USER'"""$USER"
echo $USER
echo $?
echo $PWD/file
echo "$PWD/file"
echo "text" "text$USER" ... "$USER"
echo $PWD

exit

exit 0 0
exit 42 42
exit -42 -24
exit 42
exit 259
exit -12030
exit --1239312
exit ++++1203020103
exit +0
exit ++++++0
exit -----0
exit azerty
exit "1"
exit "+102"
exit "1230"
exit "+++1230"
exit "1"23
exit "2"32"32"
exit "'42'"
exit +'42'"42"42
exit -'42'"42"42
exit 9223372036854775807
exit 9223372036854775808
exit echo something
exit exit

export

env | grep "_="
export | grep "SHLVL"
export | grep "OLDPWD"
export | grep "PWD"
export $?
export TEST
export TEST=
export TEST=123
export ___TEST=123
export --TEST=123
export ""=""
export ''=''
export "="="="
export '='='='
export TE\\\ST=100
export TE-ST=100
export -TEST=100
export TEST-=100
export _TEST=100
export TES=T=""
export export
export TES^T=123
export TEST A=5 B= A+=7
export TEST A="5 B= A+=7"

pipes

env | grep "_="
env | grep "SHLVL"
echo oui | cat -e
echo oui | echo non | echo something | grep oui
echo oui | echo non | echo something | grep non
echo oui | echo non | echo something | grep something
ifconfig | grep ":"
ifconfig | grep nothing
whoami | grep $USER
whoami | grep $USER > tmp/file
whoami | cat -e | cat -e > tmp/file
cat Makefile | grep "FLAGS"
cat Makefile | cat -e | cat -e
cat Makefile | grep "FLAGS" | grep "FLAGS" | cat -e
export TEST=123 | cat -e | cat -e
unset TEST | cat -e
whereis ls | cat -e | cat -e > test

unset

unset
unset doesntexist
unset PWD
unset OLDPWD
unset PATH
unset TES.T
unset TES+T
unset TES=T
unset -TEST
unset _TEST
unset TES_T
unset TES$?T
unset +++++++
unset ________
unset export

mixed

echo $PWD
echo $PWD|cat -e
echo $PWD hallo | cat -e
echo '$PWD hallo | cat -e'
export TEST=1 test=2 sup= | env
wc < Makefile -l | cat -e > outfile | echo hello | rev > outfile2
< test.txt < Makefile<README.md wc -l|cat -e | rev
< Makefile cat > out | < README.md cat -e
< README.md cat -e | <Makefile cat
< in1 cat -e | < in2 cat
< in1 cat -e > out1 | < in2
env | rev | head -5 | cat -e | rev
echo ok"hello"ok1"mfg" == echo ok'hello'ok1'mfg' -- okhellook1mfg
echo okhellook1"mfg" == echo okhellook1'mfg' -- okhellook1mfg
echo "o""k       "hellook1 == echo 'o''k       'hellook1 -- ok       hellook1
echo '"***hello***"'
"***hello***"
echo "'***hello***'"
"***hello***'
echo ok"'hello'"ok1"hello1"ok2
echo "text"   "$USER"    "$USER"
echo """"""""$USER""""""""
echo "'$USER'"

expansions and redirections

echo '$PWD hallo | cat -e'

echo $"PWD$PATHaa"

echo '$"PWD$PATHaa"'

echo $PWD'echo'$ 123 $$$

echo $PWD'echo1231$$$$$$'$ 123 $$$

echo $PWD'$?'

echo $PWD $? $? $HOME$? $'12345'

echo **joinable_content_$PWD$PWD$PWD$**

echo '**joinable_content_'$PWD$PWD$PWD$**

echo "hello$"

echo "hello$$$"$PWD""$PWD

echo $HOME$? $'test'

echo $HOME$?$? $'test'

echo $PWD $pwd $CWD $$$ '@@"$PWD"'

echo $PWD'$?'"$???"

echo $PWD"$" $PWD$ $HOME"$"$HOME$

echo "$PWD" > out

echo $PWD $pwd $CWD $$$ '@@"$PWD"'"''"  $HOME   "''"

echo $PWD $pwd $CWD $$$ '@@"$PWD"'"''" aaa$HOMEaaa "''”

echo > merge_text dont_merge!

echo test > test | grep

>t1>t2>t3

< hello < hello2

<< 1 << 2 hello > t1 > t2 world | t3 >> shouldnt >> t4 open

< infile1 cat > out

< infile1 cat > out | < infile1 cat > out2

ls | ls -l | cat infile1

< infile1 cat | ls

< infile1 ls > out | < infile2 cat > out2 | echo "$PWD" > out3

< infile1 ls > out | < infile2 cat > out2 | echo $PWD > out3

echo "$PWD" > out1 | < infile1 cat > out2 | < out2 ls -l > out3

< infile1 ls > out -l

cat infile1 | cat

cat infile1 > out | cat | cat | ls > out2 | cat nofile | < infile2 cat > out3

cat infile1 > out | cat | cat | ls > out2 | cat nofile | < infile2 cat > out3 | echo SHOULD_PRINT

cat infile1 > out | echo SHOULD_PRINT

cat infile1 | echo bla

**echo bla > out | grep ls**

ls -la | cat > out | < infile | cat

**< infile | cat | < in**

**< infile cat > badfd**

cat badfd | /bin/ls | cat | cat > out1 | << stop cat > out2

<in cmd "str1 str2 str3" | cmd2 -arg | cmd3 >out >out2cmd "str1 str2 str3" >out | cmd2 -arg | cmd3 >out2 >out3

cmd "str1 str2 str3" >out | cmd2 -arg str | cmd3 str >out2 >out3

< in1 < in2

< in1 cat < in2

< Makefile > outfile > out

cat /dev/urandom | head -1 > out

echo $PWD"$" $PWD$ $HOME"$"$HOME$ '//( . )( . )\\'

Contributing

If you have a suggestion that would make this better, please fork the repo and create a pull request. You can also simply open an issue with the tag "enhancement". Don't forget to give the project a star! Thanks again!

Acknowledgments

Many thanks for useful advices, support and patience to:

Didar 😎 [https://github.com/4funoO/]

Heleen 💟 [https://github.com/heleenoomen]