plugin_klish: The "prompt" symbol understands hex codes.

The prompt body can contain something like this "\x1b". This hex
number will be converted to the byte. The string must contain
exactly two characters (hex digits).

plugins/klish/misc.c

@@ -11,6 +11,7 @@
 #include <sys/types.h>
 #include <sys/utsname.h>
 
+#include <faux/conv.h>
 #include <faux/str.h>
 #include <faux/list.h>
 #include <faux/sysdb.h>
@@ -128,6 +129,24 @@ int klish_prompt(kcontext_t *context)
 				faux_str_cat(&prompt, "\x1b");
 				break;
 				}
+			// Hexadecimal byte
+			case 'x': {
+				char c;
+				char hs[3] = {};
+				if (*(pos + 1) == '\0')
+					break;
+				if (*(pos + 2) == '\0') {
+					pos++;
+					break;
+				}
+				hs[0] = *(pos + 1);
+				hs[1] = *(pos + 2);
+				pos += 2;
+				if (!faux_conv_atouc(hs, &c, 16))
+					break;
+				faux_str_catn(&prompt, &c, 1);
+				break;
+				}
 			// Hostname
 			case 'h': {
 				struct utsname buf;