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Add user-defined commands via lush.commands table (issue #30)

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User commands run in forked children like external commands, so they
support piping, redirection, and capture seamlessly.
This commit is contained in:
Cormac Shannon
2026-03-21 19:34:29 +00:00
parent fbb7b441c3
commit 973dd90d65
2 changed files with 126 additions and 0 deletions
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57
lcmd.c
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@@ -607,6 +607,57 @@ static void read_pipes (int fd_out, int fd_err,
}
/* ===== user command dispatch (runs in forked child) ===== */
/*
** Look up argv[0] in lush.commands. If found, call the function with
** all argv strings, extract an exit code, and _exit(). This must only
** be called inside a fork()ed child process.
** Returns 0 if not a user command (caller should fall through to execvp).
*/
static int exec_user_command (lua_State *L, ParsedArgs *pa) {
int i, code = 0;
lua_rawgeti(L, LUA_REGISTRYINDEX, LUA_RIDX_LUSH);
if (!lua_istable(L, -1)) {
lua_pop(L, 1);
return 0;
}
if (lua_getfield(L, -1, "commands") != LUA_TTABLE) {
lua_pop(L, 2);
return 0;
}
if (lua_getfield(L, -1, pa->argv[0]) != LUA_TFUNCTION) {
lua_pop(L, 3);
return 0;
}
lua_remove(L, -2); /* remove commands table */
lua_remove(L, -2); /* remove lush table */
for (i = 0; i < pa->argc; i++)
lua_pushstring(L, pa->argv[i]);
if (lua_pcall(L, pa->argc, 1, 0) != LUA_OK) {
/* write error to stderr and exit with failure */
const char *err = lua_tostring(L, -1);
if (err) {
(void)write(STDERR_FILENO, err, strlen(err));
(void)write(STDERR_FILENO, "\n", 1);
}
_exit(1);
}
/* extract exit code from return value */
if (lua_isinteger(L, -1)) {
code = (int)lua_tointeger(L, -1);
} else if (lua_istable(L, -1)) {
if (lua_getfield(L, -1, "code") == LUA_TNUMBER)
code = (int)lua_tointeger(L, -1);
lua_pop(L, 1);
}
fflush(stdout);
fflush(stderr);
_exit(code);
return 1; /* unreachable */
}
/* ===== pipeline execution ===== */
/*
@@ -797,6 +848,7 @@ static int exec_pipeline (lua_State *L, char **stages, int nstages,
close(err_pipe[0]); close(err_pipe[1]);
}
exec_user_command(L, &pa[i]);
execvp(pa[i].argv[0], pa[i].argv);
/* exec failed */
@@ -1050,6 +1102,7 @@ int lushCmd_command (lua_State *L) {
sa_new.sa_handler = SIG_DFL;
sigaction(SIGPIPE, &sa_new, NULL);
exec_user_command(L, &pa);
execvp(pa.argv[0], pa.argv);
/* exec failed — write error to stderr and exit */
@@ -1201,6 +1254,7 @@ int lushCmd_interactive (lua_State *L) {
sigaction(SIGINT, &sa_new, NULL);
sigaction(SIGQUIT, &sa_new, NULL);
exec_user_command(L, &pa);
execvp(pa.argv[0], pa.argv);
/* exec failed */
@@ -1287,6 +1341,9 @@ LUAMOD_API int luaopen_lush (lua_State *L) {
/* create aliases subtable */
lua_createtable(L, 0, 4);
lua_setfield(L, -2, "aliases");
/* create commands subtable for user-defined commands */
lua_createtable(L, 0, 4);
lua_setfield(L, -2, "commands");
/* intern function name strings for OP_LUSH VM access */
lushname[LUSH_OP_COMMAND] = luaS_new(L, "command");
lushname[LUSH_OP_INTERACTIVE] = luaS_new(L, "interactive");