The aim of this project is to implement our own shell with limited functionality (it's mini). It allows to get better understanding of UNIX command-line interpreter.
Requirements
The shell should:
-
Display a prompt when waiting for a new command.
-
Have a working history.
-
Search and launch the right executable (based on the PATH variable or using a relative or an absolute path).
-
Not use more than one global variable. Think about it. You will have to explain its purpose.
-
Not interpret unclosed quotes or special characters which are not required by the subject such as \ (backslash) or ; (semicolon).
-
Handle
’
(single quote) which should prevent the shell from interpreting the metacharacters in the quoted sequence. -
Handle
"
(double quote) which should prevent the shell from interpreting the metacharacters in the quoted sequence except for $ (dollar sign). -
Implement redirections:
<
should redirect input.>
should redirect output.<<
should be given a delimiter, then read the input until a line containing the delimiter is seen.>>
should redirect output in append mode.
-
Implement pipes (
|
character). The output of each command in the pipeline is connected to the input of the next command via a pipe. -
Handle environment variables (
$
followed by a sequence of characters) which should expand to their values. -
Handle
$?
which should expand to the exit status of the most recently executed foreground pipeline. -
Handle ctrl-C, ctrl-D and ctrl-\ which should behave like in bash.
-
In interactive mode:
- ctrl-C displays a new prompt on a new line.
- ctrl-D exits the shell.
- ctrl-\ does nothing.
-
Your shell must implement the following builtins:
echo
with option -ncd
with only a relative or absolute pathpwd
with no optionsexport
with no optionsunset
with no optionsenv
with no options or argumentsexit
with no options
The program can be compiled on both MacOS and Linux.
make
./minishell
or
make && ./minishell
• Signals
After pressing CTRL-C echo $?
should display exit status 1
• Check fd’s leaks / проверить незакрытые fd (файловые дескрипторы)
ls -l /proc/<pid>/fd
lsof -p <pid>
#or
lsof -c <executable>
• Redirections
ls -l -a -p > file > file2 > file3
# redirections can precede or follow the command
< file1 < file2 wc -l < file3 > outfile >> outfile1 >> outfile2
# wc should read from last heredoc end3
cat -e << lim | wc -l << end < infile << end2 < infile1 << end3
# out2 shouldn't be created
cat -e > out > out1 > no_permission > out2
• Pipes
ls -l -a -p | awk '{print $1}' | cat -e
cat /dev/random | head -c 100 | wc -c
yes | head -c 100 | cat -e > out
time -p sleep 3 | echo toto
many pipes
echo test | cat -e | cat -e | cat -e | cat -e | cat -e | cat -e | cat -e | cat -e | cat -e | cat -e| cat -e| cat -e| cat -e| cat -e| cat -e| cat -e| cat -e| cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e|cat -e > out
• Echo
[minishell]-> echo -nnnnnnnnnnn -n -n -n -n -n -n -n -nnnnnnnl TOTO
-nnnnnnnl TOTO[minishell]->
[minishell]-> $? + $?
minishell: 0: command not found
[minishell]-> echo $? + $?
127 + 127
• cd
[minishell]-> export HOME="MY_HOME"
[minishell]-> export
declare -x COLORFGBG="15;0"
declare -x COLORTERM="truecolor"
declare -x HOME="MY_HOME"
[minishell]-> cd ~
bash: cd: MY_HOME: No such file or directory