# 第一部、導讀

Shell 是個指令的直譯器（interpreter），不僅是作業系統核心與使用者之間的絕緣層，還是一種相當強大的程式語言。一個 shell 程式，也稱為 script（腳本），是一種易於使用的工具，結合系統呼叫、工具、實用程式和編譯的二進位制檔案來構建應用程式。實際上，整個 UNIX 指令、公用程式和工具都可以由shell指令集進行呼叫。如果這還不夠，內建的 shell 指令（如測試和迴圈結構）提供 script 提供了額外的功能和彈性。Shell script 特別適合用於管理系統任務和其他例行性的重複任務，這些務實的工作不需要用到那些結構嚴謹的程式語言。


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