#!/bin/bash
 
echo {1,2,3,4,5}{a,b,c,d,e,f}
 
# result : 1a 1b 1c 1d 1e 1f 2a 2b 2c 2d 2e 2f 3a 3b 3c 3d 3e 3f 4a 4b 4c 4d 4e 4f 5a 5b 5c 5d 5e 5f

#!/bin/bash
 
I=foobar
 
 
#trailing substitution
echo ${I%bar}
# result :foo
 
 
#leading substitution
echo ${I#foo}
# result :bar
 
#full substitution
STR="the wall is black"
echo ${STR/black/blue}
 
# result : the wall is blue

#!/bin/bash
 
 
F="hello HELLO"
 
echo ${F^^}
# result : HELLO HELLO
 
 
echo ${F,,}
# result :hello hello

#!/bin/bash
 
 
F="abcdefgh"
echo ${F:5:3}
 
# result : fgh
 
 
echo ${#F}
# result : 8

#!/bin/bash
 
F="my_file.log"
echo ${F%.log}.txt
 
# result : my_file.txt

#!/bin/bash
 
 
for F in `find . -name "*.java"` ; do
  echo $F
  # rename .java to .txt
  mv $F ${F%.java}.txt
done  

#!/bin/bash
 
 
# list of arguments passed to script as string
echo $*
 
# list of arguments passed to script as delimited list
echo $@
 
#number of arguments passed to current script
echo $# 
 
# name of shell script (relative path from the current directory)
echo $0 
 
# argument 1
echo $1
 
#pid of the current shell
echo $$
 
 
 
 
bash -c "exit 24"
#last exit status
echo $?
 
#PID of the most recent background ( empty if not set)
echo "PID :"$!
cat /proc/cpuinfo >/dev/null &
echo "PID :"$!
 
 
#the (input) field separator 
echo -n "$IFS" | od -abc
 
SET="1 2 3 4 5"
 
for I in $SET ; do  echo "I="$I ;done
 
# result : 
#I=1
#I=2
#I=3
#I=4
#I=5
 
IFS=':'
echo -n "$IFS" | od -abc
 
for I in $SET ; do   echo "I="$I ;done
# result : 
#I=1 2 3 4 5
 
 

touch 'test test'
IFS=$'\n'
for F in `find . -name "* *"` ; do
   OLDF=`echo $F | sed -e 's# #\ #g'`
   echo $OLDF   
   NEWF=`echo $F | sed -e 's/ /_/g'`
   echo $NEWF
   mv $OLDF $NEWF
done