Start working on parsing/scanning.

Too many changes to list them all individually.

24 files changed, 891 insertions, 34 deletions

diff --git a/.gitignore b/.gitignore
index eba84db..e5afc7d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -48,3 +48,6 @@ aplwc-*.tar.*
 /scripts/publish-release-docs
 /doc/aplwc.cp
 /doc/aplwc.cps
+/.gdb_history
+/lib/.gdb_history
+/src/.gdb_history
diff --git a/lib/Makefile.am b/lib/Makefile.am
index ac8555b..9644940 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -4,9 +4,23 @@ noinst_HEADERS = aplwc_internal.h
 
 libaplwc_la_SOURCES = \
 	autocomplete.c \
+	eval.c \
+	exit.c \
+	free_ast.c \
+	free_eval_context.c \
 	lookup_syscmd.c \
 	new.c \
-	register_syscmd.c
+	new_eval_context.c \
+	output.c \
+	parse.c \
+	register_syscmd.c \
+	run_line.c \
+	running.c \
+	scan_line.c \
+	strdup.c \
+	syscmd_output.c \
+	syscmd_error.c \
+	voutput.c
 
 libaplwc_la_LDFLAGS = -version-info 0:0:0
 
diff --git a/lib/aplwc.h b/lib/aplwc.h
index aef2495..6bfdf40 100644
--- a/lib/aplwc.h
+++ b/lib/aplwc.h
@@ -21,14 +21,23 @@
 #ifndef APLWC_H
 #define APLWC_H
 
+#include <stddef.h>
+#include <stdbool.h>
+
 struct aplwc;
 
 struct aplwc_syscmd {
 	const char *name;
+	void (*run)(struct aplwc *, struct aplwc_syscmd *, char *);
 };
 
-struct aplwc *aplwc_new(void);
+struct aplwc *aplwc_new(void *(*)(size_t), void (*)(void *), void *(*)(void *, size_t));
 char **aplwc_autocomplete(struct aplwc *, const char *, int, int);
 void aplwc_register_syscmd(struct aplwc *, struct aplwc_syscmd *);
+void aplwc_syscmd_error(struct aplwc *, struct aplwc_syscmd *, const char *, ...);
+void aplwc_syscmd_output(struct aplwc *, struct aplwc_syscmd *, const char *, ...);
+void aplwc_run_line(struct aplwc *, const char *);
+void aplwc_exit(struct aplwc *);
+bool aplwc_running(struct aplwc *);
 
 #endif /* APLWC_H */
diff --git a/lib/aplwc_internal.h b/lib/aplwc_internal.h
index 99c16ee..dd676fb 100644
--- a/lib/aplwc_internal.h
+++ b/lib/aplwc_internal.h
@@ -21,11 +21,74 @@
 #ifndef APLWC_INTERNAL_H
 #define APLWC_INTERNAL_H
 
+#include <stdarg.h>
+#include <stdbool.h>
+
+enum aplwc_token_tag {
+	APLWC_TOKEN_SYSCMD,
+	APLWC_TOKEN_SYSCMD_ARGS,
+	
+	APLWC_TOKEN_ERROR,
+};
+
+enum aplwc_ast_tag {
+	APLWC_AST_SYSCMD,
+
+	APLWC_AST_ERROR,
+};
+
 struct aplwc {
+	void *(*alloc)(size_t);
+	void (*free)(void *);
+	void *(*realloc)(void *, size_t);
+	
 	struct aplwc_syscmd **syscmds;
 	int n_syscmds;
+        bool running;
+};
+
+struct aplwc_eval_context {
+	struct aplwc *aplwc;
+	char *text;
+	size_t offset;
+	size_t length;
+
+	size_t n_tokens;
+	struct aplwc_token **tokens;
+
+	size_t token_offset;
+	struct aplwc_ast *ast;
+};
+
+struct aplwc_token {
+	enum aplwc_token_tag tag;
+	size_t offset_start;
+	size_t offset_end;
+	
+	union {
+	} data;
+};
+
+struct aplwc_ast {
+	enum aplwc_ast_tag tag;
+
+	union {
+		struct {
+			struct aplwc_syscmd *syscmd;
+			char *args;
+		} syscmd;
+	} data;
 };
 
 struct aplwc_syscmd *aplwc_lookup_syscmd(struct aplwc *, const char *);
+struct aplwc_eval_context *aplwc_new_eval_context(struct aplwc *);
+void aplwc_scan_line(struct aplwc_eval_context *, const char *);
+void aplwc_parse(struct aplwc_eval_context *);
+void aplwc_eval(struct aplwc_eval_context *);
+void aplwc_free_eval_context(struct aplwc_eval_context *);
+void aplwc_free_ast(struct aplwc *, struct aplwc_ast *);
+char *aplwc_strdup(struct aplwc *, const char *);
+void aplwc_output(struct aplwc *, const char *, ...);
+void aplwc_voutput(struct aplwc *, const char *, va_list);
 
 #endif /* APLWC_INTERNAL_H */
diff --git a/lib/autocomplete.c b/lib/autocomplete.c
index 12a8cdc..9a33ea3 100644
--- a/lib/autocomplete.c
+++ b/lib/autocomplete.c
@@ -44,10 +44,24 @@ aplwc_autocomplete(struct aplwc *aplwc, const char *line, int start, int end)
 	memcpy(word, line+start, len);
 	word[len] = 0;
 
-	if(start == 0 && word[0] == ')')
-		completions = generate(aplwc, word, completions_syscmd);
+	struct aplwc_eval_context *context = aplwc_new_eval_context(aplwc);
+	aplwc_scan_line(context, line);
+	struct aplwc_token *tok = NULL;
+	for(size_t i = 0; (i < context->n_tokens) && (tok == NULL); i++)
+		if(((size_t)start >= context->tokens[i]->offset_start) && ((size_t)end <= context->tokens[i]->offset_end + 1))
+			tok = context->tokens[i];
+
+	if(tok)
+		switch(tok->tag) {
+		case APLWC_TOKEN_SYSCMD:
+			completions = generate(aplwc, word, completions_syscmd);
+			break;
+		default:
+			break;
+		}
 	free(word);
-	
+
+	aplwc_free_eval_context(context);
 	return completions;
 }
 
@@ -64,7 +78,7 @@ generate(struct aplwc *aplwc, const char *word, char *(*fn)(struct completion_st
 
 	char *c;
 	int index = 0;
-	while(c = fn(&state)){
+	while((c = fn(&state))){
 		index++;
 		completions = realloc(completions, sizeof(*completions) * (index + 1));
 		completions[index-1] = c;
@@ -79,7 +93,7 @@ completions_syscmd(struct completion_state *state)
 {
 	struct aplwc_syscmd *syscmd;
 
-	while(syscmd = state->aplwc->syscmds[state->num++]){
+	while((syscmd = state->aplwc->syscmds[state->num++])){
 		const char *name = syscmd->name;
 		if(strncmp(name, state->word+1, state->wordlen-1) == 0){
 			int len = strlen(name);
diff --git a/lib/eval.c b/lib/eval.c
new file mode 100644
index 0000000..6eaaddf
--- /dev/null
+++ b/lib/eval.c
@@ -0,0 +1,38 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_eval(struct aplwc_eval_context *context)
+{
+	struct aplwc_syscmd *syscmd;
+	
+	switch(context->ast->tag){
+	case APLWC_AST_SYSCMD:
+		syscmd = context->ast->data.syscmd.syscmd;
+		syscmd->run(context->aplwc, syscmd, context->ast->data.syscmd.args);
+		break;
+	case APLWC_AST_ERROR:
+		printf("cannot evaluate since parsing failed\n");
+	}
+}
diff --git a/lib/exit.c b/lib/exit.c
new file mode 100644
index 0000000..d2c89b8
--- /dev/null
+++ b/lib/exit.c
@@ -0,0 +1,28 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_exit(struct aplwc *aplwc)
+{
+	aplwc->running = false;
+}
diff --git a/lib/free_ast.c b/lib/free_ast.c
new file mode 100644
index 0000000..5db6633
--- /dev/null
+++ b/lib/free_ast.c
@@ -0,0 +1,38 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_free_ast(struct aplwc *aplwc, struct aplwc_ast *ast)
+{
+	if(ast == NULL)
+		return;
+	
+	switch(ast->tag){
+	case APLWC_AST_SYSCMD:
+		break;
+	case APLWC_AST_ERROR:
+		break;
+	}
+
+	aplwc->free(ast);
+}
diff --git a/lib/free_eval_context.c b/lib/free_eval_context.c
new file mode 100644
index 0000000..5af5220
--- /dev/null
+++ b/lib/free_eval_context.c
@@ -0,0 +1,70 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+static void free_token(struct aplwc_eval_context *, struct aplwc_token *);
+static void free_ast(struct aplwc_eval_context *, struct aplwc_ast *);
+
+void
+aplwc_free_eval_context(struct aplwc_eval_context *context)
+{
+	context->aplwc->free(context->text);
+	for(size_t i = 0; i < context->n_tokens; i++)
+		free_token(context, context->tokens[i]);
+	free_ast(context, context->ast);
+	context->aplwc->free(context->tokens);
+	context->aplwc->free(context);
+}
+
+static void
+free_token(struct aplwc_eval_context *context, struct aplwc_token *tok)
+{
+	if(tok == NULL)
+		return;
+	
+	switch(tok->tag){
+	case APLWC_TOKEN_SYSCMD:
+		break;
+	case APLWC_TOKEN_SYSCMD_ARGS:
+		break;
+	case APLWC_TOKEN_ERROR:
+		break;
+	}
+
+	context->aplwc->free(tok);
+}
+
+static void
+free_ast(struct aplwc_eval_context *context, struct aplwc_ast *ast)
+{
+	if(ast == NULL)
+		return;
+	
+	switch(ast->tag){
+	case APLWC_AST_SYSCMD:
+		break;
+	case APLWC_AST_ERROR:
+		break;
+	}
+
+	context->aplwc->free(ast);
+}
diff --git a/lib/new.c b/lib/new.c
index 4454f47..6c11fca 100644
--- a/lib/new.c
+++ b/lib/new.c
@@ -24,13 +24,18 @@
 #include "aplwc_internal.h"
 
 struct aplwc *
-aplwc_new(void)
+aplwc_new(void *(*alloc)(size_t), void (*free)(void *), void *(*realloc)(void *, size_t))
 {
-	struct aplwc *aplwc = malloc(sizeof(*aplwc));
+	struct aplwc *aplwc = alloc(sizeof(*aplwc));
 	memset(aplwc, 0, sizeof(*aplwc));
 
-	aplwc->syscmds = malloc(sizeof(aplwc->syscmds[0]));
+	aplwc->alloc = alloc;
+	aplwc->free = free;
+	aplwc->realloc = realloc;
+	
+	aplwc->syscmds = aplwc->alloc(sizeof(aplwc->syscmds[0]));
 	aplwc->syscmds[0] = NULL;
+	aplwc->running = true;
 
 	return aplwc;
 }
diff --git a/lib/new_eval_context.c b/lib/new_eval_context.c
new file mode 100644
index 0000000..01b5656
--- /dev/null
+++ b/lib/new_eval_context.c
@@ -0,0 +1,35 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+struct aplwc_eval_context *
+aplwc_new_eval_context(struct aplwc *aplwc)
+{
+	struct aplwc_eval_context *context = aplwc->alloc(sizeof(*context));
+	memset(context, 0, sizeof(*context));
+	
+	context->aplwc = aplwc;
+	
+	return context;
+}
diff --git a/lib/output.c b/lib/output.c
new file mode 100644
index 0000000..87fa766
--- /dev/null
+++ b/lib/output.c
@@ -0,0 +1,31 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_output(struct aplwc *aplwc, const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	aplwc_voutput(aplwc, fmt, args);
+	va_end(args);
+}
diff --git a/lib/parse.c b/lib/parse.c
new file mode 100644
index 0000000..0bf2396
--- /dev/null
+++ b/lib/parse.c
@@ -0,0 +1,100 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+static enum aplwc_token_tag peek(struct aplwc_eval_context *);
+static struct aplwc_token *match(struct aplwc_eval_context *, enum aplwc_token_tag);
+static void emit(struct aplwc_eval_context *, enum aplwc_ast_tag, struct aplwc_ast **);
+static char *token_text(struct aplwc_eval_context *, struct aplwc_token *);
+static void parse_syscmd(struct aplwc_eval_context *, struct aplwc_ast **);
+
+void
+aplwc_parse(struct aplwc_eval_context *context)
+{
+	context->token_offset = 0;
+
+	if(peek(context) == APLWC_TOKEN_SYSCMD)
+		parse_syscmd(context, &context->ast);
+
+	if(context->ast == NULL)
+		emit(context, APLWC_AST_ERROR, &context->ast);
+}
+
+static enum aplwc_token_tag
+peek(struct aplwc_eval_context *context)
+{
+	enum aplwc_token_tag tag = -1;
+	
+	if(context->token_offset < context->n_tokens)
+		tag = context->tokens[context->token_offset]->tag;
+	return tag;
+}
+
+static struct aplwc_token *
+match(struct aplwc_eval_context *context, enum aplwc_token_tag tag)
+{
+	struct aplwc_token *tok = NULL;
+	
+	if(peek(context) == tag)
+		tok = context->tokens[context->token_offset++];
+	return tok;
+}
+
+static void
+emit(struct aplwc_eval_context *context, enum aplwc_ast_tag tag, struct aplwc_ast **ast)
+{
+	if((*ast) != NULL)
+		aplwc_free_ast(context->aplwc, *ast);
+	
+	*ast = context->aplwc->alloc(sizeof(**ast));
+	memset(*ast, 0, sizeof(**ast));
+	(*ast)->tag = tag;
+}
+
+static char *
+token_text(struct aplwc_eval_context *context, struct aplwc_token *tok)
+{
+	size_t len = tok->offset_end - tok->offset_start + 1;
+	char *text = context->aplwc->alloc(len + 1);
+	memcpy(text, context->text + tok->offset_start, len);
+	text[len] = 0;
+	return text;
+}
+
+static void
+parse_syscmd(struct aplwc_eval_context *context, struct aplwc_ast **ast)
+{
+	struct aplwc_token *tok = match(context, APLWC_TOKEN_SYSCMD);
+
+	char *name = token_text(context, tok);
+	struct aplwc_syscmd *syscmd = aplwc_lookup_syscmd(context->aplwc, name+1);
+	context->aplwc->free(name);
+	
+	if(syscmd){
+		emit(context, APLWC_AST_SYSCMD, ast);
+		(*ast)->data.syscmd.syscmd = syscmd;
+		(*ast)->data.syscmd.args = aplwc_strdup(context->aplwc, "");
+	}else
+		emit(context, APLWC_AST_ERROR, ast);
+}
diff --git a/lib/run_line.c b/lib/run_line.c
new file mode 100644
index 0000000..22f6055
--- /dev/null
+++ b/lib/run_line.c
@@ -0,0 +1,34 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_run_line(struct aplwc *aplwc, const char *line)
+{
+	struct aplwc_eval_context *context = aplwc_new_eval_context(aplwc);
+
+	aplwc_scan_line(context, line);	
+	aplwc_parse(context);
+	aplwc_eval(context);
+	aplwc_free_eval_context(context);
+}
diff --git a/lib/running.c b/lib/running.c
new file mode 100644
index 0000000..3a235ff
--- /dev/null
+++ b/lib/running.c
@@ -0,0 +1,28 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+bool
+aplwc_running(struct aplwc *aplwc)
+{
+	return aplwc->running;
+}
diff --git a/lib/scan_line.c b/lib/scan_line.c
new file mode 100644
index 0000000..811c7cb
--- /dev/null
+++ b/lib/scan_line.c
@@ -0,0 +1,161 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+static void scan(struct aplwc_eval_context *);
+static struct aplwc_token *emit(struct aplwc_eval_context *, enum aplwc_token_tag, size_t);
+static bool at_end(struct aplwc_eval_context *);
+static void skip_whitespace(struct aplwc_eval_context *);
+static char peek(struct aplwc_eval_context *, size_t);
+static void consume(struct aplwc_eval_context *, size_t);
+static void give_up(struct aplwc_eval_context *);
+static bool scan_syscmd(struct aplwc_eval_context *);
+
+void
+aplwc_scan_line(struct aplwc_eval_context *context, const char *line)
+{
+	size_t linelen = strlen(line);
+
+	if(context->text){
+		size_t textlen = strlen(context->text);
+		context->text = context->aplwc->realloc(context->text, textlen + linelen + 2);
+		context->text[textlen] = '\n';
+		memcpy(context->text+textlen+1, line, linelen + 1);
+	}else{
+		context->text = context->aplwc->alloc(linelen+1);
+		memcpy(context->text, line, linelen + 1);
+	}
+
+	if(context->tokens){
+		for(size_t i = 0; i < context->n_tokens; i++)
+			context->aplwc->free(context->tokens[i]);
+		context->aplwc->free(context->tokens);
+	}
+	scan(context);
+}
+
+static void
+scan(struct aplwc_eval_context *context)
+{
+	context->n_tokens = 0;
+	context->tokens = NULL;
+	context->offset = 0;
+	context->length = strlen(context->text);
+
+	while(!at_end(context)){
+		bool scanned = false;
+		
+		skip_whitespace(context);
+		if(at_end(context))
+			continue;
+
+		if(context->n_tokens == 0)
+			scanned |= scan_syscmd(context);
+		
+		if(!scanned)
+			give_up(context);
+	}
+}
+
+static struct aplwc_token *
+emit(struct aplwc_eval_context *context, enum aplwc_token_tag tag, size_t length)
+{
+	struct aplwc_token *tok = context->aplwc->alloc(sizeof(*tok));
+	context->n_tokens++;
+	context->tokens = context->aplwc->realloc(context->tokens, sizeof(*context->tokens) * context->n_tokens);
+	context->tokens[context->n_tokens-1] = tok;
+
+	memset(tok, 0, sizeof(*tok));
+	tok->tag = tag;
+	tok->offset_start = context->offset;
+	tok->offset_end = tok->offset_start + length - 1;
+
+	consume(context, length);
+	
+	return tok;
+}
+
+static bool
+at_end(struct aplwc_eval_context *context)
+{
+	return context->offset == context->length;
+}
+
+static void
+skip_whitespace(struct aplwc_eval_context *context)
+{
+	for(;;){
+		char c = peek(context, 0);
+		if((c == ' ') || (c == '\t'))
+			consume(context, 1);
+		else
+			break;
+	}
+}
+
+static char
+peek(struct aplwc_eval_context *context, size_t offset)
+{
+	size_t index = context->offset + offset;
+	if(index < context->length)
+		return context->text[index];
+	else
+		return 0;
+}
+
+static void
+consume(struct aplwc_eval_context *context, size_t n)
+{
+	context->offset += n;
+}
+
+static void
+give_up(struct aplwc_eval_context *context)
+{
+	emit(context, APLWC_TOKEN_ERROR, context->length - context->offset);
+}
+
+static bool
+scan_syscmd(struct aplwc_eval_context *context)
+{
+	if(peek(context, 0) != ')')
+		return false;
+
+	size_t len;
+	
+	/* Scan the syscmd itself */
+	for(len = 1; !((peek(context, len) == 0) || (peek(context, len) == ' ')); len++);
+	emit(context, APLWC_TOKEN_SYSCMD, len);
+
+	/* Skip the leading whitespace */
+	skip_whitespace(context);
+
+	/* Take the rest of the line as arguments */
+	for(len = 0; !((peek(context, len) == 0) || (peek(context, len) == '\n')); len++)
+		printf("arglen = %zu\n", len);
+	if(len > 0)
+		emit(context, APLWC_TOKEN_SYSCMD_ARGS, len);
+
+	return true;
+}
diff --git a/lib/strdup.c b/lib/strdup.c
new file mode 100644
index 0000000..3629de6
--- /dev/null
+++ b/lib/strdup.c
@@ -0,0 +1,32 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <string.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+char *
+aplwc_strdup(struct aplwc *aplwc, const char *str)
+{
+	size_t len = strlen(str) + 1;
+	char *x = aplwc->alloc(len);
+	memcpy(x, str, len);
+	return x;
+}
diff --git a/lib/syscmd_error.c b/lib/syscmd_error.c
new file mode 100644
index 0000000..edee676
--- /dev/null
+++ b/lib/syscmd_error.c
@@ -0,0 +1,32 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_syscmd_error(struct aplwc *aplwc, struct aplwc_syscmd *syscmd, const char *fmt, ...)
+{
+	(void)aplwc;
+	(void)syscmd;
+	(void)fmt;
+	printf("bla");
+}
diff --git a/lib/syscmd_output.c b/lib/syscmd_output.c
new file mode 100644
index 0000000..3e8702d
--- /dev/null
+++ b/lib/syscmd_output.c
@@ -0,0 +1,32 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_syscmd_output(struct aplwc *aplwc, struct aplwc_syscmd *syscmd, const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	aplwc_voutput(aplwc, fmt, args);
+	aplwc_output(aplwc, "\n");
+	va_end(args);
+}
diff --git a/lib/voutput.c b/lib/voutput.c
new file mode 100644
index 0000000..3f083ef
--- /dev/null
+++ b/lib/voutput.c
@@ -0,0 +1,30 @@
+/* Aplwc - A Programming Language With Constraints
+ *
+ * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
+ *
+ * This file is part of aplwc.
+ *
+ * Aplwc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Aplwc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <aplwc.h>
+#include "aplwc_internal.h"
+
+void
+aplwc_voutput(struct aplwc *aplwc, const char *fmt, va_list args)
+{
+	(void)aplwc;
+	vprintf(fmt, args);
+}
diff --git a/po/da.po b/po/da.po
index 791f4de..1c42365 100644
--- a/po/da.po
+++ b/po/da.po
@@ -5,7 +5,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: aplwc 0.1.6-fa0c-modified\n"
 "Report-Msgid-Bugs-To: bug-aplwc@gnu.org\n"
-"POT-Creation-Date: 2026-04-03 19:30+0200\n"
+"POT-Creation-Date: 2026-04-19 17:07+0200\n"
 "PO-Revision-Date: 2026-04-03 14:54+0200\n"
 "Last-Translator:  <>\n"
 "Language-Team: Danish\n"
@@ -16,22 +16,17 @@ msgstr ""
 "Plural-Forms: nplurals=2; plural=(n != 1);\n"
 "X-Generator: Gtranslator 49.0\n"
 
-#: src/main.c:68
+#: src/main.c:72
 #, c-format
-msgid "You typed: %s\n"
-msgstr "Du skrev: %s\n"
-
-#: src/main.c:71
-#, c-format
-msgid "bye\n"
-msgstr "farvel\n"
+msgid "Bye\n"
+msgstr ""
 
-#: src/main.c:78
+#: src/main.c:79
 #, c-format
 msgid "Copyright (C) 2026 Peter Mikkelsen\n"
 msgstr ""
 
-#: src/main.c:79
+#: src/main.c:80
 #, c-format
 msgid ""
 "License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/"
@@ -40,23 +35,46 @@ msgid ""
 "There is NO WARRANTY, to the extent permitted by law.\n"
 msgstr ""
 
-#: src/main.c:88
+#: src/main.c:89
 #, c-format
 msgid ""
 "Usage: %s [OPTION...]\n"
 "\n"
 msgstr "Brug: %s [TILVALG...]\n"
 
-#: src/main.c:89
+#: src/main.c:90
 #, c-format
 msgid "  -h, --help      display this help and exit\n"
 msgstr "  -h, --help      vis denne hjælp og afslut\n"
 
-#: src/main.c:90
+#: src/main.c:91
 #, c-format
 msgid "  -v, --version   display version information and exit\n"
 msgstr "  -v, --version   vis versionsinformation og afslut\n"
 
+#: src/syscmd.c:56 src/syscmd.c:65 src/syscmd.c:74
+#, c-format
+msgid "Unexpected: %s"
+msgstr ""
+
+#: src/syscmd.c:58
+msgid "Version 0"
+msgstr ""
+
+#: src/syscmd.c:76
+msgid ""
+"Stats...\n"
+"More stats..."
+msgstr ""
+
+#, c-format
+#~ msgid "You typed: %s\n"
+#~ msgstr "Du skrev: %s\n"
+
+#, c-format
+#~ msgid "bye\n"
+#~ msgstr "farvel\n"
+
 #, c-format
 #~ msgid "Hello from aplwc version '%s'\n"
 #~ msgstr "Hej fra aplwc version '%s'\n"
diff --git a/src/main.c b/src/main.c
index f163558..f2764d5 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,3 +1,4 @@
+
 /* Aplwc - A Programming Language With Constraints
  *
  * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
@@ -56,19 +57,19 @@ main(int argc, char *argv[])
 		}
 	}
 
-	struct aplwc *aplwc = aplwc_new();
+	struct aplwc *aplwc = aplwc_new(malloc, free, realloc);
 	init_syscmds(aplwc);
 	init_readline(aplwc);
 
 	char *line;
-	while(line = readline("      ")){
+	while(aplwc_running(aplwc) && (line = readline("      "))){
 		if(strlen(line) == 0)
 			continue;
 		add_history(line);
-		printf(_("You typed: %s\n"), line);
+		aplwc_run_line(aplwc, line);
 		free(line);
 	}
-	printf(_("bye\n"));
+	printf(_("Bye\n"));
 }
 
 static void
diff --git a/src/readline.c b/src/readline.c
index bda4df9..f03bbdb 100644
--- a/src/readline.c
+++ b/src/readline.c
@@ -24,7 +24,6 @@
 
 static struct aplwc *aplwc;
 static char **completions;
-static int completion_index;
 
 static char **complete(const char *, int, int);
 static char *get_completion(const char *, int);
@@ -52,5 +51,6 @@ complete(const char *text, int start, int end)
 static char *
 get_completion(const char *text, int state)
 {
+	(void)text;
 	return completions[state];
 }
diff --git a/src/syscmd.c b/src/syscmd.c
index 6c3d2e5..8c3a88a 100644
--- a/src/syscmd.c
+++ b/src/syscmd.c
@@ -19,18 +19,59 @@
  */
 
 #include <config.h>
+#include <string.h>
 #include "syscmd.h"
+#include "nls.h"
+
+static void syscmd_version(struct aplwc *, struct aplwc_syscmd *, char *);
+static void syscmd_exit(struct aplwc *, struct aplwc_syscmd *, char *);
+static void syscmd_stats(struct aplwc *, struct aplwc_syscmd *, char *);
 
 static struct aplwc_syscmd syscmds[] = {
-	{.name = "help"},
-	{.name = "version"},
-	{.name = "reset"},
-	{.name = "exit"},
+	{
+		.name = "version",
+		.run = syscmd_version
+	},
+	{
+		.name = "exit",
+		.run = syscmd_exit
+	},
+	{
+		.name = "stats",
+		.run = syscmd_stats
+	},
 };
 
 void
 init_syscmds(struct aplwc *aplwc)
 {
-	for(int i = 0; i < (sizeof(syscmds)/sizeof(*syscmds)); i++)
+	for(size_t i = 0; i < (sizeof(syscmds)/sizeof(*syscmds)); i++)
 		aplwc_register_syscmd(aplwc, &syscmds[i]);
 }
+
+static void
+syscmd_version(struct aplwc *aplwc, struct aplwc_syscmd *syscmd, char *input)
+{
+	if(strlen(input) > 0)
+		aplwc_syscmd_error(aplwc, syscmd, _("Unexpected: %s"));
+	else
+		aplwc_syscmd_output(aplwc, syscmd, _("Version 0"));
+}
+
+static void
+syscmd_exit(struct aplwc *aplwc, struct aplwc_syscmd *syscmd, char *input)
+{
+	if(strlen(input) > 0)
+		aplwc_syscmd_error(aplwc, syscmd, _("Unexpected: %s"));
+	else
+		aplwc_exit(aplwc);
+}
+
+static void
+syscmd_stats(struct aplwc *aplwc, struct aplwc_syscmd *syscmd, char *input)
+{
+	if(strlen(input) > 0)
+		aplwc_syscmd_error(aplwc, syscmd, _("Unexpected: %s"));
+	else
+		aplwc_syscmd_output(aplwc, syscmd, _("Stats...\nMore stats..."));
+}