libbpf-tools: fix arg_num field for positional arguments

vfsstat expects positional arguments to have arg_num starting from 0,
so update argp_parse accordingly

Signed-off-by: Connor O'Brien <connoro@google.com>
Change-Id: Ifb78d13ce638bfb9ba3ec857864fbbbc92e5720f

1 files changed, 1 insertions, 1 deletions

diff --git a/libbpf-tools/android/argp.cpp b/libbpf-tools/android/argp.cpp
index 5c39f79f..6c1b22fe 100644
--- a/libbpf-tools/android/argp.cpp
+++ b/libbpf-tools/android/argp.cpp
@@ -61,7 +61,7 @@ extern "C" error_t argp_parse(const struct argp *argp, int argc, char **argv, in
     // Handle positional arguments
     if (optind < argc) {
         for (int idx = optind; idx < argc; idx++) {
-            struct argp_state state = { .input = input, .argp = argp, .arg_num = idx };
+            struct argp_state state = { .input = input, .argp = argp, .arg_num = idx - optind };
             const error_t ret = argp->parser(ARGP_KEY_ARG, argv[idx], &state);
             if (ret) return ret;
         }