linux/shell中大小写转换

# 大小写转换示例代码

#!/bin/bash

rm -rf ./6.4.1.txt
echo "abcdEfgHiJ" > ./6.4.1.txt
File=`cat ./6.4.1.txt`
TmpFile=${File}
echo "number of target:$#"
[ $1 != "-u" ] && [ $1 != "-i" ] && { echo "please use'-u'or'-i'"; exit -1; }
echo "source str:${File}"
[ $1 == "-u" ] && { echo ${File} |tr "[a-z]" "[A-Z]"| tee -a ./6.4.1.txt; } 
[ $1 == "-i" ] && { echo ${File,,}| tee -a ./6.4.1.txt; } 
# the second way lower to upper
#[ $1 == "-i" ] && { echo ${File^^}; } 

 小写转大写

echo "abcd" |tr "[a-z]" "[A-Z]"
或
str="abcd"
echo ${str^^}

大写转小写

echo "abcd" |tr "[A-Z]" "[a-z]"
或
str="abcd"
echo ${str,,}