https://github.com/federicoponzi/myshell
A terminal shell in C
https://github.com/federicoponzi/myshell
shell
Last synced: about 2 months ago
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A terminal shell in C
- Host: GitHub
- URL: https://github.com/federicoponzi/myshell
- Owner: FedericoPonzi
- License: gpl-3.0
- Created: 2013-10-27T17:25:42.000Z (over 12 years ago)
- Default Branch: master
- Last Pushed: 2018-06-05T13:19:10.000Z (about 8 years ago)
- Last Synced: 2025-01-29T13:12:08.817Z (over 1 year ago)
- Topics: shell
- Language: C
- Homepage:
- Size: 25.4 KB
- Stars: 0
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
Myshell
========
A shell created for fun and study.
## Supported commands:
* echo
* clear
* exit
* clear
* external command
---
This shell is still a working progress! It can do basic things, but there is still a lot I wish to do!
### Todo:
* Use more complex parsing (EBNF in progress) to parse
* Handle I/O redirects.
## Soft todo:
* Handle environemnt variables
## Long todo:
* tab completition for commands
* Add basic scripting stuff: If/for/while
## Very long todo:
* Run script file. myshell batch.msh
* Source command
## LONG LONG todo:
* - Load configuration files: `~/.myshrc`
## Wanted:
* personalized prompt: add username, hostname ecc.
* STDIN STDOUT redirect: using `<`` and `>`, later maybe add `>>` for append, `>` to overwrite and `&>` support ecc.
* support for background processes: & to background, fg and bg commands. Don't exit if there are background processes.
* history: history command, up and down keys, record commands in a history file. Maybe one day add ctrl+r/ctrl+s to find ecc.
* Some nice-to-have commands: jobs, cd, history, exit, kill.
* if-then-else: basic scripting support.
----
Trying to being a bit formal here. Mysh is based on this EBNF language:
```
program := statement+ [&];
statement := command [connector]
connector := { || or && or | } statement | ; statement |
redirection := < filename or > filename
command := command_list var_args [redirection]
command_list := "echo" | "exit" | "clear" | "help" | "sleep" ..... | anyCharacterNoSapces
var_arg := term | var_arg | e
term = anyCharacterNoSpaces+ | "anyCharacterWithSpaces+"
```
cat file.txt | cat | cat | cat
cat file > out.txt
cat file > out.txt && cat out.txt | out.txt
cat 1.txt | cat < 2.txt
In future (maybe):
```
program := statement+ [&];
statement := command [connector]
connector := { || or && or | } statement | ; statement |
redirection := < filename | > filename | < filename > filename
assingment := id '=' expr
var_arg := lit | var_arg | e
term := [0-9]+ | \"[any char]\"
command := "echo" | "exit" | "clear" | "help" | "sleep"
var_arg
```
1. leggo il comando
cat file > out.txt && cat out.txt | out.txt
`cat file > out.txt`
lo aggiungo alla lista di comandi da eseguire
Leggo connector. Mi salvo qual è. Il comando AND, wrappa un comando normale, che viene eseguito solo se il codice del precedente è 0
Leggo cat out.txt. Lo salvo nella lista di comandi da eseguire
Leggo Pipe. Mi salvo l'informazione, e wrappo out.txt. Il problema è che out.txt dovrebbe essere eseguito contemporaneamente con out.txt
nella esecuzione, se il comando successivo è di tipo pipe, allora lo avvio ed eseguo la redirezione del stdout.
Prima eseguo la pipe, poi attivo il redirect dell'output.
Pseudocode for parsing the command name:
while isspace(line[i]) and line[i] != \0; # trim
line[i] = \0;
i++
while line[i] != " " && line[i] != "\0": # command name
i++;
strncpy(line, arg->command_name, i-last_index);
break;
Pseudocode for parsing the arguments:
while line[i] == " " and line[i] != \0 and line[i] != connector:
line[i] = \0;
if line[i] == '\"':
while line[i] != "\\\"":
i++;
else:
while isspace(line[i]) && line[i] |= \0:
i++;
arg =malloc();
strncpy(line+i, arg, last -i);
command->args.append(arg);