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The #! magic, details about the shebang/hash-bang mechanism | https://www.in-ulm.de/
what's special about #!

#! was a great hack to make scripts look and feel like real executable binaries.

But, as a little summary, what's special about #!? (list mostly courtesy of David Korn)

- the interpretername must not contain blanks
- the length of the #! is much smaller than the maximum path length
- $PATH is not searched for the interpreter
- (apart from an absolute path, the #! line also accepts a relative path,
- and #!interpreter is equivalent to #!./interpreter,
- however, it's not of any practical use)
- the interpreter usually must no be a #! script again
- the handling of arguments in the #! line itself is varying
- the setuid mechanism may or may not be available for the script
- there's no way to express #!$SHELL

And why shebang? In music, '#' means sharp. So just shorten #! to sharp-bang. Or it might be derived from "shell bang". All this probably under the influence of the american slang idiom "the whole shebang" (everything, the works, everything involved in what is under consideration). See also the wiktionary, jargon dictionary or Merriam-Websters. Sometimes it's also called hash-bang, pound-bang, sha-bang/shabang, hash-exclam, or hash-pling (british, isn't it?).

According to Dennis M. Ritchie (email answer to Alex North-Keys) it seems it had no name originally.
And Doug McIllroy mentioned (TUHS mailing list), that the slang for # at Bell Labs most probably was "sharp" at the time.
bourne  bash  posix  shell  shebang  unix  linux  shellscripting  history  butwhy  explained 
february 2019 by kme

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