#!/bin/sh vs #!/bin/bash filename expansion after <

[Ken Brown]

On 8/12/2020 1:54 PM, Morten Kjærulff via Cygwin wrote:
> Hi,
> 
> This script:
> 
> #!/bin/sh
> echo hello >hello.txt
> ls -l
> cat hell*
> cat < hell*
> 
> gives me:
> 
> $ ./t.sh
> total 2
> -rw-r--r-- 1 vp01mkf Domain Users  6 Aug 12 19:51 hello.txt
> -rwxr-xr-x 1 vp01mkf Domain Users 60 Aug 12 19:51 t.sh
> hello
> ./t.sh: line 5: hell*: No such file or directory
> 
> But if I change line1 to
> #!/bin/bash
> I get
> hello
> hello
> 
> Is that correct behaviour. I guess so, but why? And what is the rule?

 From https://tiswww.case.edu/php/chet/bash/POSIX:

When invoked as 'sh', Bash enters POSIX mode after reading the startup
files.

The following list is what's changed when 'POSIX mode' is in effect:

   1. Bash ensures that the 'POSIXLY_CORRECT' variable is set.

[...]

   11. Redirection operators do not perform filename expansion on the
      word in the redirection unless the shell is interactive.

[...]


Ken