makefile 计算 diff 失败

Question

当我尝试计算两个文本文件之间的

diff

时：

results.txt: file1.txt file2.txt
    diff $(word 1,$^) $(word 2,$^) > $@

我收到这个奇怪的（？）错误：

$ make
diff file1.txt file2.txt > results.txt
makefile:2: recipe for target 'results.txt' failed
make: *** [results.txt] Error 1

我的 makefile 有什么问题？

Answer 1

问题是，如果文件不同，

diff

通常具有非零退出代码。这将导致

make

推断命令失败。简单的解决方法是告诉

make

results.txt: file1.txt file2.txt
    -diff $(word 1,$^) $(word 2,$^) > $@

编辑：如果目标是完全摆脱诊断消息，那么您可以使用类似...

results.txt: file1.txt file2.txt
    diff $(word 1,$^) $(word 2,$^) > $@ || exit 0

Answer 2

为了避免消除真正的错误：

results.txt: file1.txt file2.txt
    diff $(word 1,$^) $(word 2,$^) > $@ || test $$? -eq 1