【已解决】makefile中把字符串转换为小写或大写

【背景】

折腾：

【已解决】在makefile中判断是cygwin还是Linux系统

期间，需要去把得到的Cygwin字符串转换为小写，以便更靠谱的去判断是否是cygwin系统。

【解决过程】

1.参考：

In GNU Make, how do I convert a variable to lower case?

感觉很是麻烦。

2.参考：

Bug 747206 – makefiles: add pure make uppercase/lowercase functions

看到其有建议，

在make中添加uc()和lc()

以便取代：

$(shell echo $(var) | tr '[A-Z]' '[a-z]')

3.开始以为lc是Linux下的工具呢，结果通过：

Administrator@PC-20130611GART /cygdrive/e/Dev_Root/docbook/tools/docbook-xsl-ns-1.78.1/webhelp
$ which lc
which: no lc in (/usr/local/bin:/usr/bin:/cygdrive/c/Program Files (x86)/AMD APP/bin/x86_64:/cygdrive/c/Program Files (x86)/AMD APP/bin/x86:/cygdrive/c/Program Files (x86)/NVIDIA Corporation/PhysX/Common:/cygdrive/c/Program Files/Common Files/Microsoft Shared/Windows Live:/cygdrive/c/Program Files (x86)/Common Files/Microsoft Shared/Windows Live:/cygdrive/c/Windows/system32:/cygdrive/c/Windows:/cygdrive/c/Windows/System32/Wbem:/cygdrive/c/Windows/System32/WindowsPowerShell/v1.0:/cygdrive/c/Program Files (x86)/ATI Technologies/ATI.ACE/Core-Static:/cygdrive/c/Program Files/Microsoft/Web Platform Installer:/cygdrive/c/Program Files (x86)/Microsoft ASP.NET/ASP.NET Web Pages/v1.0:/cygdrive/c/Program Files (x86)/Windows Kits/8.0/Windows Performance Toolkit:/cygdrive/c/Program Files/Microsoft SQL Server/110/Tools/Binn:/cygdrive/c/Program Files (x86)/Microsoft SQL Server/100/Tools/Binn:/cygdrive/c/Program Files/Microsoft SQL Server/100/Tools/Binn:/cygdrive/c/Program Files/Microsoft SQL Server/100/DTS/Binn:/cygdrive/c/Program Files (x86)/Windows Live/Shared:/cygdrive/c/Program Files/Java/jdk1.7.0_25/bin:/usr/bin:/cygdrive/e/Dev_Root/docbook/tools/ant/apache-ant-1.8.4/bin:/cygdrive/e/Dev_Root/docbook/tools/fop-1.0:/cygdrive/e/dev_install_root/HTML Help Workshop:/cygdrive/e/dev_install_root/TortoiseSVN/bin:/cygdrive/e/dev_install_root/Go/bin:/cygdrive/e/Dev_Root/go/bin:/cygdrive/e/dev_install_root/Mercurial:/cygdrive/e/dev_install_root/IDM Computer Solutions/UltraEdit:/usr/lib/lapack:/opt/crosstool-ng/bin)

得知，不是。

4.然后，就可以去makefile中，去测试看看当前make是否支持lc了：

去测试：

OS_NAME = $(shell uname -o)
LC_OS_NAME = lc($(OS_NAME))

checkcygwin:
	echo "OS_NAME=" $(OS_NAME)
	echo "LC_OS_NAME=" $(LC_OS_NAME)

结果还出现“/bin/sh: -c: line 0: syntax error near unexpected token `(‘”的错误了：

【已解决】makefile运行出错：/bin/sh: -c: line 0: syntax error near unexpected token `(‘，以及makefile中如何调用内置函数

5.结果是不支持lc。

所以，去换用那个tr操作var的试试：

OS_NAME = $(shell uname -o)
#LC_OS_NAME = $(lc $(OS_NAME))
LC_OS_NAME = $(shell echo $(OS_NAME) | tr '[A-Z]' '[a-z]')

checkcygwin:
	echo "OS_NAME=" $(OS_NAME)
	echo "LC_OS_NAME=" $(LC_OS_NAME)

结果是：

可以的：

Administrator@PC-20130611GART /cygdrive/e/Dev_Root/docbook/tools/docbook-xsl-ns-1.78.1/webhelp
$ make checkcygwin
echo "OS_NAME=" Cygwin
OS_NAME= Cygwin
echo "LC_OS_NAME=" cygwin
LC_OS_NAME= cygwin

【总结】

makefile中，将字符串从大写转换为小写的，可以用：

$(shell echo $(someVariable) | tr '[A-Z]' '[a-z]')

相反，makefile中，把字符串从小写转换为大写则用：

$(shell echo $(someVariable) | tr '[a-z]' '[A-Z]')

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