为什么我的 envsubst 命令只插入空白字符串？

Question

我正在尝试运行命令envsubst < myfile来替换环境变量，但它们不是被它们的值替换，而是被替换为空白字符串。

这是我的示例命令（为了清楚起见，分成单独的行）：

SIGNOFF="Goodbye"
&&
printf "\nOkay, \$SIGNOFF has been set to \"$SIGNOFF\"\n\nOriginal contents:\n\n"
&&
cat test.conf
&&
printf "\n\nContents after envsubst < test.conf\n\n"
&&
envsubst < test.conf | cat
&&
printf "\n\n"

这是我的结果：

$ SIGNOFF="Goodbye" && printf "\nOkay, \$SIGNOFF has been set to \"$SIGNOFF\"\n\nOriginal contents:\n\n" && cat test.conf && printf "\n\nContents after envsubst < test.conf\n\n" && envsubst < test.conf | cat && printf "\n\n"

Okay, $SIGNOFF has been set to "Goodbye"

Original contents:

Hello world, let's change the variable in the quotes below to say Goodbye!
"$SIGNOFF" (it certainly shouldn't just be blank!)

Contents after envsubst < test.conf

Hello world, let's change the variable in the quotes below to say Goodbye!
"" (it certainly shouldn't just be blank!)

$ 

我显然做了一些明显错误的事情，我只是有一个愚蠢的怀疑，这是那些如此明显的事情之一，我在试图找到答案时必须使自己的谷歌搜索过于复杂化

Answer 1

该变量未导出，因此对任何命令都不可见。导出它。

SIGNOFF="Goodbye"
export SIGNOFF
envsubst < file