pidstr needs 11 bytes (10 + NULL)

also use %d because index is signed int.

Found by compiler:
netstats.c:165:23: warning: ‘__builtin___snprintf_chk’ output may be truncated before the last format character [-Wformat-truncation=]
  snprintf(pidstr, 10, "%u", index);
                       ^~~~
In file included from /usr/include/stdio.h:938:0,
                 from firemon.h:24,
                 from netstats.c:20:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:64:10: note: ‘__builtin___snprintf_chk’ output between 2 and 11 bytes into a destination of size 10

1 files changed, 2 insertions, 2 deletions

diff --git a/src/firemon/netstats.c b/src/firemon/netstats.c
index ad123be50..c68e2e51b 100644
--- a/src/firemon/netstats.c
+++ b/src/firemon/netstats.c
@@ -161,8 +161,8 @@ static void print_proc(int index, int itv, int col) {
         }
 
         // pid
-        char pidstr[10];
-        snprintf(pidstr, 10, "%u", index);
+        char pidstr[11];
+        snprintf(pidstr, 11, "%d", index);
 
         // user
         char *user = get_user_name(pids[index].uid);