Move usage text into usage_str var

For consistency and readability.

Note: This also makes exactly one extra blank line be printed at the end
of every usage text, which is currently only done in the following
files:

* src/fcopy/main.c
* src/fnettrace-dns/main.c
* src/fnettrace-icmp/main.c
* src/fnettrace-sni/main.c
* src/fnettrace/main.c
* src/profstats/main.c

1 files changed, 5 insertions, 2 deletions

diff --git a/src/fnetfilter/main.c b/src/fnetfilter/main.c
index 8c0f6c297..1b0335d68 100644
--- a/src/fnetfilter/main.c
+++ b/src/fnetfilter/main.c
@@ -45,9 +45,12 @@ static char *default_filter =
 "-A OUTPUT -p tcp --dport 3479 -j DROP\n"
 "COMMIT\n";
 
+static const char *const usage_str =
+        "Usage:\n"
+        "\tfnetfilter netfilter-command destination-file\n";
+
 static void usage(void) {
-        printf("Usage:\n");
-        printf("\tfnetfilter netfilter-command destination-file\n");
+        puts(usage_str);
 }
 
 static void err_exit_cannot_open_file(const char *fname) {