make:对一个变量的替换引用不止一次? [英] make: substitution references on a variable more than once?

问题描述

在我的makefile中，干净"目标是通过使用SRC变量中的替换引用来删除.c.bak文件:

In my makefile, the 'clean' target is removing .c.bak files by using substitution references in the SRC variable:

rm -f $(SRC:.c=.c.bak)

这将导致它删除SRC变量中所有不以.c结尾的内容.

This causes it to delete everything in the SRC var that doesn't end in .c.

是否有一种优雅的方法可以对一个变量进行多个替换?例如，我也想尝试将.cpp替换为.cpp.bak ...

Is there an elegant way to do more than one substitution on a variable? I would, for example, like to also attempt to substitute .cpp with .cpp.bak...

推荐答案

如果可能为所有源文件显示备份，而不仅仅是 .c 和 .cpp 文件，您可以相应地更改替换:

If backups might appear for all the source files, not just the .c and .cpp files, you could change the substitution accordingly:

rm -f $(SRC:=.bak)

或者，如果您使用的是GNU Make，则可以使用其文本处理功能来准确指出$(SRC)中要影响的文件:

Or if you are using GNU Make, you could use its text processing functions to spell out exactly which files in $(SRC) you want to affect:

rm -f $(addsuffix .bak, $(filter %.c %.cpp,$(SRC)))

一种更经典的方法是查看如何构造$(SRC)变量的值.如果它是文件名的明确列表(应恕我直言，应该如此)，则可以从中间变量为不同类型的源文件构建它:

A more classical approach would be to look at how you construct the value for your $(SRC) variable. If it's an explicit list of filenames (as IMHO it should be) then you can build it up from intermediate variables for the different kinds of source file:

SRC_C = foo.c bar.c
SRC_CXX = baz.cpp apple.cpp
SRC = Makefile banana.pl carrot.pl $(SRC_C) $(SRC_CXX)

现在，您可以正确且方便地编写原始替换文件(即无需GNU Make工具):

Now you can write your original substitution correctly and portably (i.e., without requiring GNU Make facilities):

rm -f $(SRC_C:.c=.c.bak) $(SRC_CXX:.cpp=.cpp.bak)

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