List all supported format sequences in the output of "--help".

src/include/pv.h

@@ -275,6 +275,11 @@ extern void pv_sig_fini(pvstate_t);
  */
 extern void pv_state_free(/*@only@*/ pvstate_t);
 
+/*
+ * Return a string listing all supported format sequences.
+ */
+/*@null@*/ char *pv_format_sequences(void);
+
 #if ! HAVE_SETPROCTITLE
 void initproctitle(int, char **);
 void setproctitle(const char *, ...);

src/main/help.c

@@ -434,6 +434,7 @@ void display_help(void)
 	size_t right_margin = 77;
 	const char *program_description;
 	const char *bug_report_note;
+	char *format_sequences = NULL;
 	unsigned int terminal_width = 0, terminal_height = 0;
 
 	pv_screensize(&terminal_width, &terminal_height);
@@ -593,6 +594,21 @@ void display_help(void)
 		printf("\n");
 	}
 
+	format_sequences = pv_format_sequences();
+	if (NULL != format_sequences) {
+		const char *format_sequence_header;
+		format_sequence_header = _("Supported format sequences:");
+		if (NULL != format_sequence_header) {
+			printf("\n");
+			display_word_wrap(format_sequence_header, right_margin, 0);
+			printf("\n");
+		}
+		printf("\n  ");
+		display_word_wrap(format_sequences, right_margin, 2);
+		free(format_sequences);
+		printf("\n");
+	}
+
 	printf("\n");
 
 	bug_report_note = _("Please report any bugs to: %s");

src/pv/display.c

@@ -1329,6 +1329,42 @@ static struct pvdisplay_component_s {
 };
 
 
+/*
+ * Return a pointer to a malloc()ed string containing a space-separated list
+ * of all supported format sequences.  The caller should free() it.
+ */
+/*@null@ */
+char *pv_format_sequences(void)
+{
+	size_t component_idx, buffer_size, offset;
+	char *buffer;
+
+	buffer_size = 0;
+	for (component_idx = 0; NULL != format_component[component_idx].match; component_idx++) {
+		size_t component_sequence_length = strlen(format_component[component_idx].match);	/* flawfinder: ignore */
+		/* flawfinder - static strings, guaranteed null-terminated. */
+		buffer_size += 2 + component_sequence_length;	/* 2 for '%' + ' ' */
+	}
+
+	buffer = malloc(buffer_size + 1);
+	if (NULL == buffer)
+		return NULL;
+
+	offset = 0;
+	for (component_idx = 0; NULL != format_component[component_idx].match; component_idx++) {
+		size_t component_sequence_length = strlen(format_component[component_idx].match);	/* flawfinder: ignore - as above */
+		if (0 != offset)
+			buffer[offset++] = ' ';
+		buffer[offset++] = '%';
+		memmove(buffer + offset, format_component[component_idx].match, component_sequence_length);
+		offset += component_sequence_length;
+	}
+
+	buffer[offset] = '\0';
+	return buffer;
+}
+
+
 /*
  * Initialise the output format structure, based on the current options.
  */