Executor

Walks the AST and runs each node: simple commands, pipelines, logical operators, subshells, blocks, and background jobs.

defines the executor functions for handling AST nodes.

Author

zweng, pulgamecanica

Defines

MAX_PIPELINE
MAX_SAVED_FDS

Functions

int executor_execute(struct s_shell *shell, t_ast *ast)

Main dispatch function for executing AST nodes.

Parameters:

  • shell – Pointer to the central shell state

  • ast – Pointer to the AST node to execute

Returns:

Exit status code

int execute_simple_command(struct s_shell *shell, t_cmd *cmd)

Node-type executors.

Parameters:

  • shell – Pointer to the central shell state

  • ast – Pointer to the AST node to execute

Returns:

Exit status code

int execute_pipeline(struct s_shell *shell, t_ast *ast)
int execute_and(struct s_shell *shell, t_ast *ast)
int execute_or(struct s_shell *shell, t_ast *ast)
int execute_sequence(struct s_shell *shell, t_ast *ast)
int execute_subshell(struct s_shell *shell, t_ast *ast)
int execute_block(struct s_shell *shell, t_ast *ast)
int execute_background(struct s_shell *shell, t_ast *ast)
int setup_redirections(t_list *redirs, int saved_fds[3])

redirection setup

redirection setup

If saved_fds is not NULL, save stdin/stdout/stderr first (for restore).

Parameters:

  • redirs – List of redirection nodes

  • saved_fds – Array to save original file descriptors

  • redirs – The list of redirections.

  • saved_fds – The array to store the saved file descriptors.

Returns:

Exit status code

Returns:

0 on success, -1 on error.

void restore_redirections(int saved_fds[3])

Restore redirections.

Restore redirections.

Parameters:

  • saved_fds – Array of saved file descriptors

  • saved_fds – The array of saved file descriptors.

int setup_heredoc(t_redir *redir)

Heredoc setup.

Heredoc setup.

the write end, close the write end, and return the read end fd.

Parameters:

  • redir – Pointer to the redirection node

  • redir – The redirection structure.

Returns:

Exit status code

Returns:

The read-end fd on success, -1 on error.

char *find_command(struct s_shell *shell, const char *name)

Command search (PATH)

Parameters:

  • shell – Pointer to the central shell state

  • name – Name of the command to search for

Returns:

Pointer to the found command, or NULL if not found

void exec_pipeline_external(struct s_shell *shell, t_cmd *cmd)

Pipeline helper (called from pipe_child, does not return)

Parameters:

  • shell – Pointer to the central shell state

  • cmd – Pointer to the command node

int get_exit_status(int wstatus)

get exit status from wait status

get exit status from wait status

  • Normal exit: WEXITSTATUS (0-255)

    • Killed by signal: 128 + signal number

Parameters:

  • wstatus – Wait status code

  • wstatus – The waitpid status.

Returns:

Exit status code

Returns:

The shell exit code.

void split_assignment(const char *assign, char **name, char **value)

Split “NAME=value” at first ‘=’ into separate name and value strings.

Caller must free both *name and *value.

If no ‘=’ found, *name = dup of assign, *value = dup of “”.

Parameters:

  • assign – The assignment string.

  • name – The pointer to store the name.

  • value – The pointer to store the value.

executor.c — Dispatch

Command execution functionality for 42sh.

Author

wengzhang, pulgamecanica

Functions

static int dispatch_node(t_shell *shell, t_ast *ast)
int executor_execute(t_shell *shell, t_ast *ast)

exec_command.c — Simple Commands

Command execution functionality for 42sh.

Author

wengzhang, pulgamecanica

Functions

static void apply_assignments(t_shell *shell, t_list *assigns, int do_export)

Apply assignments permanently to shell variables.

Used when command is empty (bare assignment) or in child for execve.

Parameters:

  • shell – The shell instance.

  • assigns – The list of assignments.

  • do_export – Whether to export the variables.

static int exec_assignment_only(t_shell *shell, t_cmd *cmd)

Handle empty command (just assignments and/or redirections).

Example: FOO=bar or FOO=bar > file

Parameters:

  • shell – The shell instance.

  • cmd – The command structure.

Returns:

0 on success, 1 on failure.

static int save_and_apply_assigns(t_shell *shell, t_list *assigns, char **old_names, char **old_vals)

Save old values, apply temporary assignments for builtin scope.

old_names/old_vals arrays store what to restore afterward.

Parameters:

  • shell – The shell instance.

  • assigns – The list of assignments.

  • old_names – Array to store old variable names.

  • old_vals – Array to store old variable values.

Returns:

Count of saved assignments.

static void restore_assigns(t_shell *shell, char **old_names, char **old_vals, int count)

Restore old variable values after builtin execution.

Parameters:

  • shell – The shell instance.

  • old_names – Array of old variable names.

  • old_vals – Array of old variable values.

  • count – Number of assignments to restore.

static int exec_builtin(t_shell *shell, t_cmd *cmd, t_builtin_fn fn)

Execute a builtin with temporary assignments and redirections.

Assignments are scoped to this command only, then restored.

Parameters:

  • shell – The shell instance.

  • cmd – The command structure.

  • fn – The builtin function to execute.

Returns:

The exit status of the builtin.

static void exec_child(t_shell *shell, t_cmd *cmd)

Child process: apply assignments, set up redirections, exec.

Parameters:

  • shell – The shell instance.

  • cmd – The command structure.

int execute_simple_command(t_shell *shell, t_cmd *cmd)

exec_logical.c — &&, ||, ;

Logical command execution functionality for 42sh.

Author

wengzhang, pulgamecanica

Functions

int execute_and(t_shell *shell, t_ast *ast)

Execute logical AND operation.

cmd1 && cmd2 : run right only if left succeeds (exit 0)

Parameters:

  • shell – The shell instance.

  • ast – The abstract syntax tree node.

Returns:

The exit status of the operation.

int execute_or(t_shell *shell, t_ast *ast)

Execute logical OR operation.

cmd1 || cmd2 : run right only if left fails (exit != 0)

Parameters:

  • shell – The shell instance.

  • ast – The abstract syntax tree node.

Returns:

The exit status of the operation.

int execute_sequence(t_shell *shell, t_ast *ast)

Execute sequential commands.

cmd1 ; cmd2 : run both, return status of right

Parameters:

  • shell – The shell instance.

  • ast – The abstract syntax tree node.

Returns:

The exit status of the operation.

exec_pipeline.c — Pipes

Pipeline command execution functionality for 42sh.

Author

wengzhang, pulgamecanica

Functions

static int collect_pipeline(t_ast *ast, t_ast **cmds, int max)

Flatten nested PIPE nodes left-to-right into a flat array.

Example: (A | B) | C => [A, B, C]

Parameters:

  • ast – The abstract syntax tree node.

  • cmds – The array to store the pipeline commands.

  • max – The maximum number of commands to store.

Returns:

The number of commands collected.

static void close_pipes(int pipes[][2], int count)

Close all pipe fds in the array.

Parameters:

  • pipes – The array of pipe file descriptors.

  • count – The number of pipes to close.

static void pipe_child(t_shell *shell, t_ast *cmd_ast, int pipes[][2], int info[3])

Execute a single pipeline stage in the child process.

Wire stdin/stdout from pipes, then exec or run builtin.

Parameters:

  • shell – The shell instance.

  • cmd_ast – The abstract syntax tree node for the command.

  • pipes – The array of pipe file descriptors.

  • info – The information array for the pipeline stage.

void exec_pipeline_external(t_shell *shell, t_cmd *cmd)

Execute external command in pipeline child (does not return).

Parameters:

  • shell – The shell instance.

  • cmd – The command structure.

int execute_pipeline(t_shell *shell, t_ast *ast)

exec_subshell.c — Subshell, Block, Background

Functions

int execute_subshell(t_shell *shell, t_ast *ast)

Execute a command in a subshell.

( cmd ) - runs in a forked child (subshell).

Parameters:

  • shell – The shell instance.

  • ast – The abstract syntax tree node.

Returns:

The exit status of the command.

int execute_block(t_shell *shell, t_ast *ast)

Execute a command block.

{ cmd; } - runs in the current shell, but with its own redirections.

Parameters:

  • shell – The shell instance.

  • ast – The abstract syntax tree node.

Returns:

The exit status of the command.

int execute_background(t_shell *shell, t_ast *ast)

Execute a background command.

cmd & - runs in a forked child with its own process group.

Parameters:

  • shell – The shell instance.

  • ast – The abstract syntax tree node.

Returns:

The exit status of the command.

redirections.c — I/O Redirections

Functions

static int redir_get_fd(t_redir *redir)
static int redir_open_file(t_redir *redir)
static int apply_dup_redir(t_redir *redir, int target_fd)
static int apply_one_redir(t_redir *redir)
int setup_redirections(t_list *redirs, int saved_fds[3])

Set up all redirections in the list.

redirection setup

If saved_fds is not NULL, save stdin/stdout/stderr first (for restore).

Parameters:

  • redirs – The list of redirections.

  • saved_fds – The array to store the saved file descriptors.

Returns:

0 on success, -1 on error.

void restore_redirections(int saved_fds[3])

Restore stdin/stdout/stderr from saved fds, then close the saved copies.

Restore redirections.

Parameters:

saved_fds – The array of saved file descriptors.

heredoc.c — Here-documents

Heredoc functionality for 42sh.

Author

wengzhang, pulgamecanica

Functions

int setup_heredoc(t_redir *redir)

Set up a heredoc: create a pipe, write the collected content to.

Heredoc setup.

the write end, close the write end, and return the read end fd.

Parameters:

redir – The redirection structure.

Returns:

The read-end fd on success, -1 on error.

command_search.c — PATH Lookup

Command search functionality for 42sh.

Author

wengzhang, pulgamecanica

Functions

static char *build_path(const char *dir, const char *name)

Build “dir/name” path. Caller must free the result.

Parameters:

  • dir – The directory path.

  • name – The file name.

Returns:

The full path, or NULL if allocation fails.

static void free_split(char **arr)

Search each directory in PATH for an executable named name.

Parameters:

  • path_var – The PATH environment variable.

  • name – The command name.

Returns:

Heap-allocated full path, or NULL if not found.

static char *search_path(const char *path_var, const char *name)

Search each directory in PATH for an executable named name.

Parameters:

  • path_var – The PATH environment variable.

  • name – The command name.

Returns:

Heap-allocated full path, or NULL if not found.

char *find_command(t_shell *shell, const char *name)

Find an executable command.

  • If name contains ‘/’, treat it as a path directly.

    • Otherwise search each directory in $PATH.

Parameters:

  • shell – The shell instance.

  • name – The command name.

Returns:

Heap-allocated path on success, NULL on failure.

exec_utils.c — Utilities

Utility functions for command execution in 42sh.

Author

wengzhang, pulgamecanica

Functions

int get_exit_status(int wstatus)

Convert raw waitpid status to shell exit code.

get exit status from wait status

  • Normal exit: WEXITSTATUS (0-255)

    • Killed by signal: 128 + signal number

Parameters:

wstatus – The waitpid status.

Returns:

The shell exit code.

void split_assignment(const char *assign, char **name, char **value)

Split “NAME=value” at first ‘=’ into separate name and value strings.

Caller must free both *name and *value.

If no ‘=’ found, *name = dup of assign, *value = dup of “”.

Parameters:

  • assign – The assignment string.

  • name – The pointer to store the name.

  • value – The pointer to store the value.