shell 字符串处理

test="my name is gaole"
echo ${#test}   #get length of a string
echo ${test:4}  #get substring from 5 to the end
echo ${test:4:6}  #get substring from 5 to the following 6 characters
echo ${test:-3}  #get the last character,but some bash can't support -3
echo ${test:5:-1} #get substring from 6 and delete the last letter,but some bash can't support
test2="abdabdfebabdABDe"
echo ${test2//b/x}  #replace all gs with a 
echo ${test2/b/x} #replace the first g
echo ${test2%%*ABDe} #replace from right with 
echo ${test2%*ABDe}  #replace from right with the shortest length
echo ${test2#abd*d}   #replace from left with the shortest length
echo ${test2##abd*d}  #replace from left with the largest length
a="test121212121212121212121212"
b="test1"
if [ "test" == "test1" ] ;then #space must be write between every [ and ==
   echo "equal"
elif [[ $a == $b* ]] ;then  #double zhong kuohao will enable moshi match
   echo "contain"
else
   echo "not equal"
fi