core: add %v specifier

src/shared/install-printf.c

@@ -108,6 +108,7 @@ char *install_full_printf(InstallInfo *i, const char *format) {
          * %m the machine ID of the running system
          * %H the host name of the running system
          * %b the boot ID of the running system
+         * %v `uname -r` of the running system
          */
 
         const Specifier table[] = {
@@ -122,7 +123,8 @@ char *install_full_printf(InstallInfo *i, const char *format) {
                 { 'm', specifier_machine_id,          NULL },
                 { 'H', specifier_host_name,           NULL },
                 { 'b', specifier_boot_id,             NULL },
-                { 0, NULL, NULL }
+                { 'v', specifier_kernel_release,      NULL },
+                {}
         };
 
         assert(i);

src/shared/specifier.c

@@ -20,6 +20,7 @@
 ***/
 
 #include <string.h>
+#include <sys/utsname.h>
 
 #include "macro.h"
 #include "util.h"
@@ -145,3 +146,14 @@ char *specifier_boot_id(char specifier, void *data, void *userdata) {
 char *specifier_host_name(char specifier, void *data, void *userdata) {
         return gethostname_malloc();
 }
+
+char *specifier_kernel_release(char specifier, void *data, void *userdata) {
+        struct utsname uts;
+        int r;
+
+        r = uname(&uts);
+        if (r < 0)
+                return NULL;
+
+        return strdup(uts.release);
+}

src/shared/specifier.h

@@ -36,3 +36,4 @@ char *specifier_string(char specifier, void *data, void *userdata);
 char *specifier_machine_id(char specifier, void *data, void *userdata);
 char *specifier_boot_id(char specifier, void *data, void *userdata);
 char *specifier_host_name(char specifier, void *data, void *userdata);
+char *specifier_kernel_release(char specifier, void *data, void *userdata);