listamsb: add -c (check only) option.

1 files changed, 14 insertions, 3 deletions

diff --git a/listamsb.c b/listamsb.c
index efa0621..5d9b425 100644
--- a/listamsb.c
+++ b/listamsb.c
@@ -34,8 +34,9 @@ const char *self;
 
 char pipe_command[BUFSIZ + 1] = { "a8cat" };
 
-int verbose = 0;
-int raw_output = 0;
+int verbose = 0;     /* -v */
+int raw_output = 0;  /* -a */
+int check_only = 0;  /* -c */
 
 int need_pclose = 0;
 int bytes_read = 0;
@@ -208,6 +209,7 @@ void print_help(void) {
 	puts("By B. Watson <urchlay@slackware.uk>, released under the WTFPL");
 	printf("Usage: %s [-a] [-v] [-h] [-i] [-u] [-t] [-m] [-s] [file]\n", self);
 	puts("  -a: raw ATASCII output");
+	puts("  -c: check only (no listing)");
 	puts("  -v: verbose");
 	puts("  -h: show this help");
 	puts("  -i -u -t -m -s: passed to a8cat (try 'a8cat -h')");
@@ -218,8 +220,9 @@ void parse_args(int argc, char **argv) {
 	char tmp[10];
 	int opt;
 
-	while( (opt = getopt(argc, argv, "vaiutmsh")) != -1) {
+	while( (opt = getopt(argc, argv, "cvaiutmsh")) != -1) {
 		switch(opt) {
+			case 'c': check_only = 1; break;
 			case 'a': raw_output = 1; break;
 			case 'h': print_help(); exit(0);
 			case 'v': verbose = 1; break;
@@ -257,6 +260,14 @@ void parse_args(int argc, char **argv) {
 }
 
 void open_output() {
+	if(check_only) {
+		outfile = freopen("/dev/null", "wb", stdout);
+		if(!outfile) {
+			fprintf(stderr, "%s: ", self);
+			perror("/dev/null");
+			exit(1);
+		}
+	}
 	if(raw_output) {
 		if(isatty(fileno(stdout)))
 			die("refusing to write raw ATASCII to a terminal");