Exit status rules

Standard values

Status	Meaning	Where set
0	Success	Default return from commands
1	General error	Builtin failures, fork errors
2	Misuse / syntax error	process_input() on parse fail or exit with non-numeric arg
126	Permission denied / is directory	handle_exec_error()
127	Command not found	exec_cmd_not_found()
128+N	Killed by signal N	wait_for_child() and wait_for_pipe_children()
130	SIGINT (128+2)	main_loop() after Ctrl-C
131	SIGQUIT (128+3)	wait_for_child() via WIFSIGNALED

Where $? is updated

shell->exit_status is set in exactly 1 place in the main flow, in handle_input():

⠀
  shell->exit_status = process_input(input, shell);
⠀

main_loop() overrides it to 130 when g_signal == SIGINT after readline()

Builtin exit behavior

Case	Behavior
exit (no args)	returns shell->exit_status
exit N	returns N casted to unsigned char (wrapped to 0–255)
exit abc	prints error, returns 2, sets running = 0 (exits)
exit 1 2	prints "too many arguments" and returns 1 (does NOT exit)