Quote alias values in the output of the alias(1) builtin so they are

suitable for re-input to the shell (SUSv3)

bin/sh/alias.c

@@ -207,8 +207,11 @@ aliascmd(int argc, char **argv)
 
 		for (i = 0; i < ATABSIZE; i++)
 			for (ap = atab[i]; ap; ap = ap->next) {
-				if (*ap->name != '\0')
-				    out1fmt("alias %s=%s\n", ap->name, ap->val);
+				if (*ap->name != '\0') {
+					out1fmt("alias %s=", ap->name);
+					out1qstr(ap->val);
+					out1c('\n');
+				}
 			}
 		return (0);
 	}
@@ -217,8 +220,11 @@ aliascmd(int argc, char **argv)
 			if ((ap = lookupalias(n, 0)) == NULL) {
 				outfmt(out2, "alias: %s not found\n", n);
 				ret = 1;
-			} else
-				out1fmt("alias %s=%s\n", n, ap->val);
+			} else {
+				out1fmt("alias %s=", n);
+				out1qstr(ap->val);
+				out1c('\n');
+			}
 		else {
 			*v++ = '\0';
 			setalias(n, v);

bin/sh/output.c

@@ -107,6 +107,11 @@ out1str(const char *p)
 	outstr(p, out1);
 }
 
+void
+out1qstr(const char *p)
+{
+	outqstr(p, out1);
+}
 
 void
 out2str(const char *p)
@@ -114,6 +119,11 @@ out2str(const char *p)
 	outstr(p, out2);
 }
 
+void
+out2qstr(const char *p)
+{
+	outqstr(p, out2);
+}
 
 void
 outstr(const char *p, struct output *file)
@@ -124,10 +134,31 @@ outstr(const char *p, struct output *file)
 		flushout(file);
 }
 
+/* Like outstr(), but quote for re-input into the shell. */
+void
+outqstr(const char *p, struct output *file)
+{
+	char ch;
+
+	out1c('\'');
+	while ((ch = *p++) != '\0') {
+		switch (ch) {
+		case '\'':
+			/*
+			 * Can't quote single quotes inside single quotes;
+			 * close them, write escaped single quote, open again.
+			 */
+			outstr("'\\''", file);
+			break;
+		default:
+			outc(ch, file);
+		}
+	}
+	out1c('\'');
+}
 
 char out_junk[16];
 
-
 void
 emptyoutbuf(struct output *dest)
 {

bin/sh/sh.1

@@ -1268,6 +1268,8 @@ With no arguments, the
 builtin command prints the names and values of all defined aliases
 (see
 .Ic unalias ) .
+Alias values are written with appropriate quoting so that they are
+suitable for reinput to the shell.
 .It Ic bg Op Ar job ...
 Continue the specified jobs
 (or the current job if no jobs are given)