use of :

作者: lucientlau | 来源:发表于2017-12-12 10:39 被阅读0次

: nop command

:
echo $?  # 0

$? the previous command return value

Dead loop

while :
do 
   operation-1
  .
  .
  .
done

the same with

while ture
do

done

Another example

if condition
then :
else
  take some action
fi

: ${username=`whoami`}

: > file
cat /dev/null > file

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