init: Add support for writing system property value to a file in init.rc
The write command will write a property value if the value starts with a "$'
For example:
write /sys/class/android_usb/iSerial $ro.serialno
Use double leading '$' if you need to write a string that starts with '$':
write /data/foo $$hello
to write "$hello" to /data/foo
Change-Id: I55431ac7715a5347bb95c3a15aee97c575444dde
diff --git a/init/builtins.c b/init/builtins.c
index 23ef224..dad7545 100644
--- a/init/builtins.c
+++ b/init/builtins.c
@@ -527,7 +527,23 @@
int do_write(int nargs, char **args)
{
- return write_file(args[1], args[2]);
+ char *path = args[1];
+ char *value = args[2];
+ if (value[0] == '$') {
+ /* Write the value of a system property if value starts with '$' */
+ value++;
+ if (value[0] != '$') {
+ value = property_get(value);
+ if (!value) {
+ ERROR("property %s has no value for writing to %s\n", value, path);
+ return -EINVAL;
+ }
+ } /* else fall through to support double '$' prefix for writing
+ * string literals that start with '$'
+ */
+ }
+
+ return write_file(path, value);
}
int do_copy(int nargs, char **args)