Makefile:使用多行字符串作为命令的输入

Question

我希望使用多行json编码的字符串作为makefile中命令的输入。现在，似乎没有任何东西传递给命令watchman-typescript或watchman-debug。

Makefile

.PHONY: typescript
typescript:
    tsc --target ES5 ts/main.ts

.PHONY: watch
watch:
    watchman watch .

define WATCHMAN_TYPESCRIPT_TRIGGER =
["trigger", "./ts", {
  "name": "tsTrigger",
  "expression": ["suffix", "ts"],
  "command": ["make", "typescript"]
}]
endef

.PHONY: watchman-typescript
watchman-typescript:
    watchman -j '$(WATCHMAN_TYPESCRIPT_TRIGGER)'

.PHONY: watchman-debug
watchman-debug:
    echo $(WATCHMAN_TYPESCRIPT_TRIGGER)

Answer 1

虽然这在make本身看来是不可能的--最终将变量的每一行解释为食谱中的命令--但有一个解决办法:您可以将变量导出为shell变量，并在命令中引用该变量。这就是：

define WATCHMAN_TYPESCRIPT_TRIGGER =
["trigger", "./ts", {
  "name": "tsTrigger",
  "expression": ["suffix", "ts"],
  "command": ["make" "typescript"]
}]
endef

# export as shell variable
export WATCHMAN_TYPESCRIPT_TRIGGER

# ...

# use shell variable in the command. $$ in make means $ in the shell command.
watchman-typescript:
    watchman -j "$$WATCHMAN_TYPESCRIPT_TRIGGER"

Answer 2

在makefile中，可以使用行延拓字符 \将某些内容拆分为多行：

define WATCHMAN_TYPESCRIPT_TRIGGER = \
["trigger", "./ts", { \
  "name": "tsTrigger", \
  "expression": ["suffix", "ts"], \
  "command": ["make" "typescript"] \
}] \
endef