Makefile中如何给变量赋值？

Question

在尝试测试 Makefile 中的命令失败时（在本例中为 jekyll build relative），变量 $$? 应包含最后一个命令的退出代码。在测试中，此代码显示为 127。但是，我想将其分配给变量 LAST_EXIT，以便下一个 if 语句可以检查执行的命令是成功还是失败。

问题是 LAST_EXIT 从未收到分配给它的值，如下面的代码所示。关于如何解决这个问题有什么建议吗？

代码：

LAST_EXIT = 0

all:
    @echo "Building the website... Running command:"
    - jekyll build relative || LAST_EXIT=$$?
    - jekyll build relative || echo $$? and $(LAST_EXIT)
ifeq ($(LAST_EXIT), 0)
    #echo a message indicating success

输出：

jekyll build relative || LAST_EXIT=$?
/bin/sh: jekyll: command not found
jekyll build relative || echo $? and 0
/bin/sh: jekyll: command not found
127 and 0

Answer 1

你的方法有两个问题。

1) Make 在执行任何规则之前解析 makefile 的条件部分。这个：

all:
    LAST_EXIT=0
ifeq ($(LAST_EXIT), 0)
    #echo a message indicating success 
endif

不会报告成功（除非您将 LAST_EXIT 的值设置在规则之上的某处）。

2) 配方中的每个命令都在其自己的子程序中执行shell； shell 变量值不从一行到下一行保留：

all:
    LAST_EXIT=5; echo the value is $$LAST_EXIT
    @echo now the value is $$LAST_EXIT

这应该有效：

all:
    - jekyll build relative || LAST_EXIT=$$?; \
  if [ $$LAST_EXIT == 0 ]; then  echo success!; fi

Answer 2

我对这个问题的解决方案是在 Makefile 中调用以下脚本来检查 Jekyll：（称为 ./{scriptName}

#!/bin/bash

LINEBREAK="*****************************************************************"
VERSION=0

echo "Checking Jekyll..."
VERSION=$(jekyll --version)

if test "$?" == "0"
then
     echo "$VERSION is installed on this system..."
else
     echo "$LINEBREAK"
     echo "Oops! It looks like you don't have Jekyll yet, lets install it!"
     echo "Running command: \"sudo gem install jekyll\""
     echo "$LINEBREAK"
     sudo gem install jekyll
     if test "$?" != "0"
     then
          echo "$LINEBREAK"
          echo "Jekyll install failed... It needs to be installed as a super-user on your system, which"
          echo "requires your password. You can run \"sudo gem install jekyll\" yourself to install Jekyll."
          echo "You can also see their website at: \"https://jekyllrb.com/docs/installation/\" for more information"
          echo "$LINEBREAK"
          exit 113
     else
          echo "$LINEBREAK"
          echo "Jekyll has been installed on this system..."
          echo "Proceeding to build..."
          echo "$LINEBREAK"
     fi
fi

exit 0

Makefile中如何给变量赋值？

How to assign value to variable in Makefile?

makefile

variable-assignment

assign