Question

所以我在我的shell程序中'if [-s $ fname]'。有人可以告诉我它的作用吗？我搜索了它，但没有关于'-s'的信息。

if [ -s $fname ]
then 
   echo -e "\tname\tph\t\tcity\tpin\tstate"
  cat $fname
else
  echo -e "\nfile is empty"
 fi
;;

这是我的代码的一部分，其中-s用于你需要它。谢谢！

Answer 1

你的问题本身就有答案： - ）

如果变量-s $fname中的文件存在且非空，则

True表达式求值为$fname。因此，如果$fname文件不存在或为空，那么您的其他屏蔽将被激活并且代码段打印为file is empty

几个例子，

fname="test.txt"

## case when the file is not existing
if [ -s $fname ]
then 
   echo -e "case-1: $fname exists and is not empty"
  cat $fname
else
  echo -e "case-1: $fname do not exists or is empty"
fi

## case when the file exists but is of empty size
touch $fname

if [ -s $fname ]
then 
   echo -e "case-2: $fname exists and is not empty"
  cat $fname
else
  echo -e "case-2: $fname do not exists or is empty"
fi

## case when the file exists and is having contents too
echo "now its not empty anymore" > $fname

if [ -s $fname ]
then 
   echo -e "case-3: $fname exists and is not empty"
   cat $fname
else
  echo -e "case-3: $fname do not exists or is empty"
fi

输出是，

case-1: test.txt do not exists or is empty
case-2: test.txt do not exists or is empty
case-3: test.txt exists and is not empty
now its not empty anymore

什么是shell中'if [-s filename]'的含义？

1 个答案: