shell基礎学習における文字列操作、for循環文の例

#!/bin/bash
my_name="jxq"
echo $my_name
echo ${my_name}
# ------------------------------------
#      
# ------------------------------------
#          ，         ：
#                ，              
#              （             ）
name="will"
age=24
my_full_name='${name}${age}'
echo ${my_full_name}
my_full_name="${name}${age}"
echo ${my_full_name}
#      
echo ${name}${age}
#      
echo ${#name} # 4
# substring
message="I want to be healthy"
echo ${message:2} # want to be health, 2 position
echo ${message:2:4} # want，2 position，4 len
# delete shortest match from front: ${string#substring}
echo ${message#*want}
# delete shortest match from back: ${string%substring}
echo ${message%healthy}
# delete longest match from front: ${string##substring}
echo ${message##*h}
# delete longest match from back: ${string%%substring}
echo ${message%%t*}
# find and replace: ${string/pattern/replacement}
book_name="Catch Eye Eye"
echo ${book_name/Eye/Cat}
# find and replace all match: ${string//pattern/replacement}
echo ${book_name//Eye/Cat}
file_path="/usr/local/bin"
# only replace when pattern match the beginning: ${string/#pattern/replacement}
echo ${file_path/#\/usr/tmp}
# only replace when pattern match the end: ${string/%pattern/replacement}
echo ${file_path/%bin/tmp}
# string index
stringZ=abcABC123ABCabc
echo `expr index "$stringZ" C12` # Mac OSX   expr

# ------------------------------------
#   
# ------------------------------------
# if
if true
then
 echo "ok, true"
fi
#     
if true; then echo "ok"; fi
var='12'
if [ $var -eq 12 ]; then 
    echo "This is a numeric comparison if example"
fi
if [ "$var" = "12" ]; then
    echo "This is a string if comparison example"
fi
if [[ "$var" = *12* ]]; then
    echo "This is a string regular expression if comparison example"
fi
name="jxq"
if [ "$name" = "jxq" ]; then
 echo "hello" $name
fi

#     
for item in `ls *.sh`
do
 echo $item
 echo "completed"
done
#     
for item in `ls *.sh`; do echo $item; echo "completed"; done;
counter=1
while :
do
 echo "bee"
 let "counter=$counter+1"
 if [ $counter -eq 3 ]; then
  break # break/continue Java  
 fi
done
# Case  
opt="install"
case "${opt}" in
 "install" )
  echo "install..."
  exit

 
 "update" )
  echo "update..."
  exit

 
 *) echo "bad opt"
esac