aash

An Average Shell

Features

• Executes commands.
• Has the ability to change the working directory with cd.
• Shows the current working directory in the prompt.
• Shows the exit status of the last command in the prompt if it is not 0.
• Supports color terminals.
• Passes on the SIGINT signal to the foreground child.
• Supports multiple commands on one line separated with ;.
• Allows redirecting stdout and stderr using >, 2>, &>, and their appending counterparts.
• Allows redirecting stdin using <.

Function Headers

aash.c

static void sighandler(int signo)

Passes SIGINT on to foreground child process, if one is currently running.

void print_prompt()

Prints a prompt to stdout.

char execute_command(char **to_run)

Forks, with the child executing a command and the parent waiting for it.
Returns 1 if the command executed is a builtin function, 0 otherwise.

int main()

The core of the shell.

input.c

struct array tokenizer(char *string, const char *delim)

Converts a string delimited by specific characters to a character array.

struct array tokenizer_whitespace(char *string)

Converts a given string separated by spaces into an array of strings.

struct array tokenizer_semicolon(char *string)

Converts a given string separated by semicolons into an array of strings.

char *get_input()

Returns dynamically allocated input read from stdin.

builtin.c

int builtin_cd(const char *argument)

A partial implementation of the cd utility, as specified by POSIX.

_Noreturn void builtin_exit(const char *argument)

A partial implementation of the exit utility, as specified by POSIX.

utilities.c

void errno_handler(int en)

A default handler for errno that prints error messages to stderr.

redirection.c

struct redir_stats get_redir_stats(char **command, char *redirection)

Given the string to work with and a redirection token to look for, it "cuts" the filename out, returning that and a flag representing if we are appending to a file.

int redirect_stdin(struct redir_stats r, struct fd *fds)

Processes redirection for stdin, returning the new file descriptor.

int redirect_stdout(struct redir_stats r, struct fd *fds)

Processes redirection for stdout, returning the new file descriptor.

int redirect_stderr(struct redir_stats r, struct fd *fds)

Processes redirection for stderr, returning the new file descriptor.

void process_redirects(char **command, struct fd *fds)

Handles redirection by calling the proper helper function(s).

void reset_redirects(struct fd *fds)

Resets redirection to the default behavior (i.e., the state of streams before redirections were processed).

Bugs

• Does not interpret "quoted strings" as a single token.

• Not all *alloc'd memory is freed before exiting in builtin_exit(). This is negligible.

• Exits with status 0 if EOF is read, regardless of the exit status of the last command.