Why do you need to put #!/bin/bash at the beginning of a script file?

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本文解释了在Bash脚本文件开头使用/bin/bash的原因，以及它如何帮助*ix shell识别脚本的解释器类型。文章还讨论了不同shell的历史背景，以及现代系统中脚本可以使用的多种解释器。

http://stackoverflow.com/questions/8967902/why-do-you-need-to-put-bin-bash-at-the-beginning-of-a-script-file

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I have made Bash scripts before and they all ran fine without this at the beginning. What's the point of putting it in? Would things be any different?

It's a convention so the *nix shell knows what kind of interpreter to run.

For example, older flavors of ATT defaulted to "sh" (the Bourne shell), while older versions of BSD defaulted to "csh" (the C shell).

Even today (where most systems run "bash", the "Bourne Again Shell"), scripts can be in bash, python, perl, ruby, PHP, etc, etc. For example, you might see "!/bin/perl" or "/bin/perl5".

PS:The exclamation mark ("!") is affectionately called "bang". The shell comment symbol ("#") is sometimes called "hash".

PPS:Remember - under *nix, associating a suffix with a file type is merely a convention, not a "rule". An "executable" can be a binary program, any one of a million script types and other things as well. Hence the need for "#!/bin/bash".