core: enhance printvars

[coffee/buildroot.git] / docs / manual / make-tips.txt

diff --git a/docs/manual/make-tips.txt b/docs/manual/make-tips.txt
index 97a3302477eb0a323a80bebe3da56b67b55f837b..ea1d825bef59b71b03fcff8181f1583294621b36 100644 (file)
--- a/docs/manual/make-tips.txt
+++ b/docs/manual/make-tips.txt
@@ -77,3 +77,57 @@ To delete all build products as well as the configuration:
 If +ccache+ is enabled, running +make clean+ or +distclean+ does
 not empty the compiler cache used by Buildroot. To delete it, refer
 to xref:ccache[].
+
+.Dumping the internal make variables:
+
+One can dump all the variables known to make, along with their values:
+
+----
+ $ make -s printvars
+ VARIABLE=value_of_variable
+ ...
+----
+
+It is possible to tweak the output using some variables:
+
+- +VARS+ will limit the listing to variables which names match the
+  specified make-pattern
+- +QUOTED_VARS+, if set to +YES+, will single-quote the value
+- +RAW_VARS+, if set to +YES+, will print the unexpanded value
+
+For example:
+
+----
+ $ make -s printvars VARS=BUSYBOX_%DEPENDENCIES
+ BUSYBOX_DEPENDENCIES=skeleton toolchain
+ BUSYBOX_FINAL_ALL_DEPENDENCIES=skeleton toolchain
+ BUSYBOX_FINAL_DEPENDENCIES=skeleton toolchain
+ BUSYBOX_FINAL_PATCH_DEPENDENCIES=
+ BUSYBOX_RDEPENDENCIES=ncurses util-linux
+----
+
+----
+ $ make -s printvars VARS=BUSYBOX_%DEPENDENCIES QUOTED_VARS=YES
+ BUSYBOX_DEPENDENCIES='skeleton toolchain'
+ BUSYBOX_FINAL_ALL_DEPENDENCIES='skeleton toolchain'
+ BUSYBOX_FINAL_DEPENDENCIES='skeleton toolchain'
+ BUSYBOX_FINAL_PATCH_DEPENDENCIES=''
+ BUSYBOX_RDEPENDENCIES='ncurses util-linux'
+----
+
+----
+ $ make -s printvars VARS=BUSYBOX_%DEPENDENCIES RAW_VARS=YES
+ BUSYBOX_DEPENDENCIES=skeleton toolchain
+ BUSYBOX_FINAL_ALL_DEPENDENCIES=$(sort $(BUSYBOX_FINAL_DEPENDENCIES) $(BUSYBOX_FINAL_PATCH_DEPENDENCIES))
+ BUSYBOX_FINAL_DEPENDENCIES=$(sort $(BUSYBOX_DEPENDENCIES))
+ BUSYBOX_FINAL_PATCH_DEPENDENCIES=$(sort $(BUSYBOX_PATCH_DEPENDENCIES))
+ BUSYBOX_RDEPENDENCIES=ncurses util-linux
+----
+
+The output of quoted variables can be reused in shell scripts, for example:
+
+----
+ $ eval $(make -s printvars VARS=BUSYBOX_DEPENDENCIES QUOTED_VARS=YES)
+ $ echo $BUSYBOX_DEPENDENCIES
+ skeleton toolchain
+----