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Unixシェルスクリプトで〜と！の違い

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Unixシェルスクリプトで〜と！の違い

シェルスクリプトのIF条件で正規表現を確認するとき〜と！間で使用する必要がある演算子は何ですか？

以下に共有されている2つのケースの間に違いはありますか？

ケース1：

if [[ $file_date != ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]]; 
then    
    echo -e "The file_date is not in the required format"; 
else
    echo "doing good";
fi

ケース2：

if [[ $file_date =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]]; 
then    
    echo -e "The file_date is not in the required format"; 
else
    echo "doing good";
fi

答え1

合計を比較することは、リンゴとオレンジを比較するのと!=同じです=~。

!=おおよそ「等しくない」を意味し、=~「一致」を意味します。[[ expression ]]この演算子の詳細についてはを参照してくださいman bash。以下は、最も関連性の高い部分を抜粋したものです。

      When the == and != operators are used, the string to the  right  of
      the  operator  is considered a pattern and matched according to the
      rules described below under Pattern Matching,  as  if  the  extglob
      shell option were enabled.  The = operator is equivalent to ==.  If
      the shell option nocasematch is enabled,  the  match  is  performed
      without  regard  to  the case of alphabetic characters.  The return
      value is 0 if the string matches (==) or does not  match  (!=)  the
      pattern, and 1 otherwise.  Any part of the pattern may be quoted to
      force the quoted portion to be matched as a string.

      An additional binary operator, =~,  is  available,  with  the  same
      precedence  as == and !=.  When it is used, the string to the right
      of the operator is considered an extended  regular  expression  and
      matched accordingly (as in regex(3)).  The return value is 0 if the
      string matches the  pattern,  and  1  otherwise.   If  the  regular
      expression is syntactically incorrect, the conditional expression's
      return value is 2.

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