Makefileでエコーをオフにする

Makefileにてデフォルトでは実行するレシピのコマンドが表示される．
これをエコー(echoing)と呼ぶ．

$ cat Makefile
help: ## show this help.
    echo "Please use 'make <target>' where <target> is one of\n"
    awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_-]+:.*?## / {sub("\\\\n",sprintf("\n%22c"," "), $$2);printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}' $(MAKEFILE_LIST)

$ make
echo "Please use 'make <target>' where <target> is one of\n"
Please use 'make <target>' where <target> is one of

awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_-]+:.*?## / {sub("\\\\n",sprintf("\n%22c"," "), $2);printf "\033[36m%-20s\033[0m %s\n", $1, $2}'  Makefile
help                 show this help.

上記実行例では，echoコマンドやawkコマンドの結果だけ出力されて欲しく，
エコーされて欲しくない．
これを解決するためにはレシピの各コマンドの前に@を付与する．

$ cat Makefile
help: ## show this help.
    @echo "Please use 'make <target>' where <target> is one of\n"
    @awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_-]+:.*?## / {sub("\\\\n",sprintf("\n%22c"," "), $$2);printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}' $(MAKEFILE_LIST)

$ make
Please use 'make <target>' where <target> is one of

help                 show this help.

こういったコマンドが大量にある場合で，
実行時にて実行するコマンド全てに適用したい場合は
-s/--silent/--quiet オプションを付与して実行する

$ cat Makefile
help: ## show this help.
    echo "Please use 'make <target>' where <target> is one of\n"
    awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_-]+:.*?## / {sub("\\\\n",sprintf("\n%22c"," "), $$2);printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}' $(MAKEFILE_LIST)

$ make -s
Please use 'make <target>' where <target> is one of

help                 show this help.

特定ターゲットに対してエコーをオフにしたい場合は
.SILENTターゲットにて対象ターゲットを指定するとよい．

$ cat Makefile
.SILENT: help
help: ## show this help.
    echo "Please use 'make <target>' where <target> is one of\n"
    awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_-]+:.*?## / {sub("\\\\n",sprintf("\n%22c"," "), $$2);printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}' $(MAKEFILE_LIST)

$ make
Please use 'make <target>' where <target> is one of

help                 show this help.