sys/shell/commands: add static qualifier where appropriate

[maribu]

Contribution description

Due to the conversion to XFA based SHELL_COMMAND() much fewer function need to expose a symbol. Hence, spray static all over the place.

Testing procedure

One could search for missing static using this regex:

$ rg '^[ \t]*int[ \t]*[a-zA-Z0-9_]*[ \t]*\([ \t]*int[ \t]*[a-zA-Z0-9_]*[ \t]*,[ \t]*char[ \t*]*[a-zA-Z0-9_]*[ \t]*\)'

Murdock will check that I didn't add a static where it shouldn't be.

Issues/PRs references

Follow up to #18152

[kaspar030]

ACK.

[maribu]

I had to remove the static again from _gnrc_neitf_config() and _gnrc_ipv6_nib() to get tests/gnrc_dhcpv6_client compiling again.

@miri64: I think that something like this would allow tests/gnrc_dhcpv6_client to work without using shell commands:

diff --git a/tests/gnrc_dhcpv6_client/main.c b/tests/gnrc_dhcpv6_client/main.c
index 19741e5752..f51ae66328 100644
--- a/tests/gnrc_dhcpv6_client/main.c
+++ b/tests/gnrc_dhcpv6_client/main.c
@@ -20,13 +20,13 @@
 #include <stddef.h>
 
 #include "net/gnrc/netif.h"
+#include "net/gnrc/ipv6/nib.h"
 #include "net/dhcpv6/client.h"
 #include "net/sock.h"
 #include "xtimer.h"
 
 static char _dhcpv6_client_stack[DHCPV6_CLIENT_STACK_SIZE];
 
-extern int _gnrc_netif_config(int argc, char **argv);
 extern int _gnrc_ipv6_nib(int argc, char **argv);
 
 void *_dhcpv6_client_thread(void *args)
@@ -55,15 +55,25 @@ void *_dhcpv6_client_thread(void *args)
 
 int main(void)
 {
-    char *pl[] = { "nib", "prefix" };
-
-    _gnrc_netif_config(0, NULL);
+    /* print all IPv6 addresses */
+    printf("At start: {\"IPv6 addresses\": [\"");
+    netifs_print_ipv6("\", \"");
+    puts("\"]}");
     thread_create(_dhcpv6_client_stack, DHCPV6_CLIENT_STACK_SIZE,
                   DHCPV6_CLIENT_PRIORITY, THREAD_CREATE_STACKTEST,
                   _dhcpv6_client_thread, NULL, "dhcpv6-client");
     xtimer_sleep(5);
     /* global address should now be configured */
-    _gnrc_netif_config(0, NULL);
-    _gnrc_ipv6_nib(2, pl);
+    printf("After 5 seconds: {\"IPv6 addresses\": [\"");
+    netifs_print_ipv6("\", \"");
+    puts("\"]}");
+    gnrc_ipv6_nib_nc_t entry;
+    void *state = NULL;
+    unsigned iface = 0U;
+
+    while (gnrc_ipv6_nib_nc_iter(iface, &state, &entry)) {
+        gnrc_ipv6_nib_nc_print(&entry);
+    }
+
     return 0;
 }

But the python test script needs to be adapted as well. The test script doesn't run on my machine, so I would rather leave this to someone else.

[maribu]

All green. 9b0cf39 got added post ACK