while loop, for loop

1. create a function to generate file with the filename start with 10 random characters

#!/bin/bash
WORK_DIR=/tmp/00
#define the function
create(){
    i=1
    while [ $i -le 5 ]
    do
       if [ ! -d $WORK_DIR ]
       then
          mkdir -p $WORK_DIR
          cd $WORK_DIR && touch `</dev/urandom tr -dc "a-z" | head -c 10`_test.txt
       else
          cd $WORK_DIR && touch `</dev/urandom tr -dc "a-z" | head -c 10`_test.txt
       fi
       i=$(( $i+1 )) 
     done
}
# invoke the function   
create

2. Using for loop to write a function to rename file in batch.　

#!/bin/bash

changeName(){
  DIR=/tmp/test01
  FILE=`ls $DIR`
  postfix=a.txt
  for i in $FILE
  do
    c=`echo $i |cut -c 1-10`
    mv $DIR/$i $DIR/$c$postfix
    echo "The file  $i was renamed to $c$postfix" 
  done

}
changeName

3. using for loop print the odd number between 1 - 100

for((i=1;i<=100;i++))
do
  if ((i%2==1))
  then
    echo $i
    continue
  fi
done

4. 　using while loop print the odd number between 1 - 100

i=1
while(($i<=100))
do
    if(($i%2==1))
    then
        echo $i
    fi
    i=$(($i+1))
done

5.  Another way to print the odd number

for i in {1..100..2}
do
   echo $i
done

6. print the file name for a folder

for f  in `ls ~`
do 
          name=`echo "$f" | awk -F. '{print $1}'`           
          echo $name
done