From: Trent Huber <trentmhuber@gmail.com>
Date: Wed, 5 Nov 2025 06:24:54 +0000 (-0500)
Subject: Introduce unalias builtin
X-Git-Url: https://trenthuber.com/code?a=commitdiff_plain;h=964fb0ce0badae9d97da38e56c93c619a26d0169;p=thus.git

Introduce unalias builtin
---

diff --git a/src/builtins/alias.c b/src/builtins/alias.c
index 4bc3f49..2eb2692 100644
--- a/src/builtins/alias.c
+++ b/src/builtins/alias.c
@@ -10,27 +10,34 @@
 #define MAXALIAS 25
 
 static struct {
-	struct {
+	struct entry {
 		char lhs[MAXCHARS - 5], *rhs;
 	} entries[MAXALIAS + 1];
 	size_t size;
 } aliases;
 
-char *getrawalias(char *token) {
+static size_t getindex(char *lhs) {
 	size_t i;
 
 	for (i = 0; i < aliases.size; ++i)
-		if (strcmp(token, aliases.entries[i].lhs) == 0) return aliases.entries[i].rhs;
+		if (strcmp(aliases.entries[i].lhs, lhs) == 0) break;
 
-	return NULL;
+	return i;
 }
 
-char **getalias(char *token) {
+char *getaliasrhs(char *lhs) {
+	size_t i;
+
+	if ((i = getindex(lhs)) == aliases.size) return NULL;
+	return aliases.entries[i].rhs;
+}
+
+char **getalias(char *lhs) {
 	char *rhs;
 	size_t l;
 	static struct context context;
 
-	if (!(rhs = getrawalias(token))) return NULL;
+	if (!(rhs = getaliasrhs(lhs))) return NULL;
 
 	while (*rhs == ' ') ++rhs;
 	strcpy(context.buffer, rhs);
@@ -46,9 +53,22 @@ char **getalias(char *token) {
 	return context.tokens;
 }
 
+int removealias(char *lhs) {
+	size_t i;
+	struct entry *entry;
+
+	if ((i = getindex(lhs)) == aliases.size) return 0;
+	entry = &aliases.entries[i];
+	memmove(entry, entry + 1, (--aliases.size - i) * sizeof(*entry));
+	for (; i < aliases.size; ++i, ++entry)
+		entry->rhs = (void *)entry->rhs - sizeof(*entry);
+
+	return 1;
+}
+
 BUILTIN(alias) {
 	size_t i;
-	char *lhs;
+	struct entry *entry;
 
 	switch (argc) {
 	case 1:
@@ -60,15 +80,13 @@ BUILTIN(alias) {
 			note("Unable to add alias `%s', maximum reached (%d)", argv[1], MAXALIAS);
 			return EXIT_FAILURE;
 		}
-		for (i = 0; i < aliases.size; ++i)
-			if (strcmp(aliases.entries[i].lhs, argv[1]) == 0) break;
 
-		lhs = aliases.entries[i].lhs;
+		entry = &aliases.entries[i = getindex(argv[1])];
 		if (i == aliases.size) {
-			strcpy(lhs, argv[1]);
+			strcpy(entry->lhs, argv[1]);
 			++aliases.size;
 		}
-		strcpy(aliases.entries[i].rhs = lhs + strlen(lhs) + 1, argv[2]);
+		strcpy(entry->rhs = entry->lhs + strlen(entry->lhs) + 1, argv[2]);
 
 		break;
 	default:
diff --git a/src/builtins/alias.h b/src/builtins/alias.h
index fc6edcb..7f2411f 100644
--- a/src/builtins/alias.h
+++ b/src/builtins/alias.h
@@ -1,2 +1,3 @@
-char *getrawalias(char *token);
-char **getalias(char *token);
+char *getaliasrhs(char *lhs);
+char **getalias(char *lhs);
+int removealias(char *lhs);
diff --git a/src/builtins/unalias.c b/src/builtins/unalias.c
new file mode 100644
index 0000000..3024cbc
--- /dev/null
+++ b/src/builtins/unalias.c
@@ -0,0 +1,10 @@
+#include <stdlib.h>
+
+#include "alias.h"
+#include "builtin.h"
+
+BUILTIN(unalias) {
+	if (argc != 2) return usage(argv[0], "lhs");
+
+	return removealias(argv[1]) ? EXIT_SUCCESS : EXIT_FAILURE;
+}
diff --git a/src/builtins/which.c b/src/builtins/which.c
index 493c75f..80a774b 100644
--- a/src/builtins/which.c
+++ b/src/builtins/which.c
@@ -39,7 +39,7 @@ char *getpath(char *file) {
 
 	type = PATH;
 	if (!(slash = strchr(file, '/'))) {
-		if ((entry = getrawalias(file))) {
+		if ((entry = getaliasrhs(file))) {
 			type = ALIAS;
 			return entry;
 		}