2.1. Invoking the script
Having written the script, you can invoke it by sh scriptname, [1] or alternatively bash scriptname.
要執行腳本，我們可以使用 「sh 腳本檔名」 或「bash 腳本檔名」來執行。
(Not recommended is using sh <scriptname, since this effectively disables reading from stdin within the script.)
(不建議使用 「sh <腳本檔名」執行腳本，因為會無法讀取stdin輸入的值。)
Much more convenient is to make the script itself directly executable with a chmod.
更方便、直接的執行方法就是用chmod指令讓腳本變成可執行。
Either: chmod 555 scriptname (gives everyone read/execute permission) [2]
chmod 555 scriptname (給所有使用者 讀/執行 的權限) [2]
or
chmod +rx scriptname (gives everyone read/execute permission)
chmod +rx scriptname (給所有使用者 讀/執行 的權限)
chmod u+rx scriptname (gives only the script owner read/execute permission)
chmod u+rx scriptname (只給腳本擁有者 讀/執行 的權限)
Having made the script executable, you may now test it by ./scriptname. [3]
想測試腳本是否是可執行的嗎？執行./scriptname測試看看。[3]
If it begins with a "sha-bang" line, invoking the script calls the correct command interpreter to run it.
若腳本的開頭有「sha-bang」這一行，則會呼叫正確的指令解譯器來運行腳本。
As a final step, after testing and debugging, you would likely want to move it to /usr/local/bin (as root, of course), to make the script available to yourself and all other users as a systemwide executable.
經過測試與除錯後，最後一步我們通常都會想將腳本搬到 /usr/local/bin 目錄下 (當然，以root身份來執行)，讓系統上所有使用者都能使用這個腳本。
The script could then be invoked by simply typing scriptname [ENTER] from the command-line.
接著我們只要打腳本名稱[按下ENTER]，就可直接執行了。
Notes
[1] Caution: invoking a Bash script by sh scriptname turns off Bash-specific extensions, and the script may therefore fail to execute.
注意：使用 sh scriptname 來執行腳本，可能會導致 Bash 相關的 extensions 無法使用，腳本也就因此執行失敗。
[2] A script needs read, as well as execute permission for it to run, since the shell needs to be able to read it.
賦予腳本「執行」權限時也須賦予「讀」的權限，因為shell在執行時需要「讀」它。
[3] Why not simply invoke the script with scriptname?
為何不乾脆用腳本名來執行腳本就好？
If the directory you are in ($PWD) is where scriptname is located, why doesn't this work?
假如現在所在的位置跟腳本同一目錄下，為何腳本無法成功執行？
This fails because, for security reasons, the current directory (./) is not by default included in a user's $PATH.
原因是考量到安全的因素，當前所在目錄(./)並不包含使用者的$PATH
It is therefore necessary to explicitly invoke the script in the current directory with a ./scriptname.
因此，此情況下若要執行腳本，就得使用./scriptname來執行。