slice: support omitting last byte

1 files changed, 14 insertions, 7 deletions

diff --git a/slice.c b/slice.c
index ec4abd2..119ecef 100644
--- a/slice.c
+++ b/slice.c
@@ -11,15 +11,22 @@
 #include <stdbool.h>
 
 int main(int argc, char **argv) {
-	if (argc < 4) {
-		fprintf(stderr, "Usage: %s file offset last-byte|+length\n", *argv);
+	char *filename;
+	unsigned long seekpos, bytes_end;
+	if (argc < 3) {
+		fprintf(stderr, "Usage: %s file offset [last-exclusive-byte|+length]\n", *argv);
 		return 1;
 	}
-	char *filename = argv[1];
-	unsigned long seekpos = strtoul(argv[2], NULL, 0);
-	unsigned long bytes_end = strtoul(argv[3], NULL, 0);
+	filename = argv[1];
+	seekpos = strtoul(argv[2], NULL, 0);
 
-	if (*argv[3] == '+') {
+	if (argc >= 4) {
+		bytes_end = strtoul(argv[3], NULL, 0);
+	} else {
+		bytes_end = -1;
+	}
+
+	if (argc >= 4 && *argv[3] == '+') {
 		if (bytes_end + seekpos < bytes_end) {
 			fprintf(stderr, "Integer overflow on the last byte\n");
 			return 1;
@@ -64,7 +71,7 @@ int main(int argc, char **argv) {
 		read_bytes += n;
 	} while (read_bytes < bytes_end);
 
-	if (read_bytes != bytes_end)
+	if (bytes_end != -1UL && read_bytes != bytes_end)
 		fprintf(stderr, "Output is truncated, missing %lu bytes.\n",
 				bytes_end - read_bytes);