0x16. C - Simple Shell
In this project we are to create a basic and simple shell, the project is a group project for two and it has seventeen tasks which inlude;
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Betty would be proud - Write a beautiful code that passes the Betty checks
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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… -
Simple shell 0.2
Simple shell 0.1 +
* Handle command lines with arguments
- Simple shell 0.3
Simple shell 0.2 +
* Handle the PATH
* fork must not be called if the command doesn’t exist
- 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
- Simple shell 1.0
Simple shell 0.4 +
* Implement the env built-in, that prints the current environment
- 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
- Simple shell 0.2.1
Simple shell 0.2 +
* You are not allowed to use strtok
- 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
- 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
- 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
- ;
Simple shell 1.0 +
* Handle the commands separator ;
- && and ||
Simple shell 1.0 +
* Handle the && and || shell logical operators
- 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
- Variables
Simple shell 1.0 +
* Handle variables replacement
* Handle the $? variable
* Handle the $$ variable
- Comments
Simple shell 1.0 +
* Handle comments (#)
- 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