Re: "here strings" and tmpfiles

[Greg Wooledge]

On Mon, Apr 08, 2019 at 10:53:46AM -0400, Chet Ramey wrote:
> On 4/8/19 10:36 AM, Greg Wooledge wrote:
> 
> > That's incorrect in this context.  We're talking about boot scripts here,
> > not interactive user shells.  In boot scripts, on every operating system
> > I've ever used, the shell being used is either POSIX sh or Bourne sh.
> 
> This is clearly wrong in general, though it might be true on systems you've
> used (e.g., Debian and Ubuntu in Linuxland). If you have a system where
> bash is installed as /bin/sh (e.g., RHEL or Fedora), that is the shell you
> use to write boot scripts.

I've used more than just Linux systems.  On most commercial Unix
derivatives, /bin/sh is either a stripped-down Korn shell variant, or
a legacy POSIX or Bourne shell.

On some systems (e.g. HP-UX 10), boot scripts use /sbin/sh which is
a statically-linked POSIX-based shell, and are only able to use other
statically linked tools from the /sbin directory, because the shared
libraries aren't mounted yet.  At least, until you get past the point
where everything is mounted.  If you're writing a boot script, YOU need
to know when and how that happens, and therefore which tools you can
use in which script.

But you're right: we actually *do* have at least one Red Hat (CentOS)
based system where /bin/sh links to bash.  It's the minority, though.