bin/21315: Shells often behave oddly when executing shell scripts

Jilles Tjoelker jilles at
Sat Apr 4 16:30:03 PDT 2009

The following reply was made to PR bin/21315; it has been noted by GNATS.

From: Jilles Tjoelker <jilles at>
To: bug-followup at, rwatson at
Subject: Re: bin/21315: Shells often behave oddly when executing shell
Date: Sun, 5 Apr 2009 01:22:34 +0200

 > Shells appear to behave oddly when executing shell scripts in a number
 > of situations.
 > (1) When the kernel discovers that the interpreter used is another
 > interpreter, it generally returns ``Exec format error'' (ENOEXEC).
 > However, when csh and sh find themselves in the same situation, they
 > don't return that error, they execute the script using their own
 > interpreter.
 In the case of sh, POSIX says that it should do this. If sh gets ENOEXEC
 or equivalent when it tries to execute something, it should execute the
 file as a shell script. Only if the file is not a text file may sh
 refuse to execute it, writing an error message and returning an exit
 status of 126. (Our sh does not use this exception, resulting in
 messages like '1: Syntax error: "(" unexpected' when trying to execute
 an ELF binary for a different architecture.)
 > (2) When in single-user mode, the sh shell appears to assume that any
 > script it runs should be executed using its own interpreter, not the
 > interpreter at the top of the file. In multi-user mode, this appears
 > to work fine.
 I have no idea about this, but it could have something to do with
 ENOEXEC as well. In particular, when this PR was written,
 was in /usr/libexec, so unavailable when /usr was not mounted.
 Jilles Tjoelker

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