shell(2) if特殊、 case判斷、for循環、while循環、break、continue

            一、 if特殊用法 1.if [ -z "$a"]   #!/bin/bash   if [ ! -f /tmp/iftest ]    then       echo "The derectory is not exist"       exit    fi    n=`wc -l /tmp/iftest`    if [ -z "$n" ]    then    ech

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