Subject: Re: discrepency beteen /bin/echo and builtin echo of /bin/sh
To: None <>
From: Greg A. Woods <>
List: current-users
Date: 06/08/2002 15:48:42
[ On Saturday, June 8, 2002 at 20:05:48 (+0100), David Laight wrote: ]
> Subject: Re: discrepency beteen /bin/echo and builtin echo of /bin/sh
> It might? be worth including print (aka ksh), you don't always want
> the complexity of printf (esp. since is isn't a builtin).

I'd VERY much rather see /bin/echo and /bin/sh's built-in echo be
conformant with SuSv2 instead (since it provides most of the
capabilities of the ksh "print" builtin without any of the portability
headache), though I guess getting a bunch of *BSD-heads to agree to give
up "echo -n", even after all these decades, is rather fruitless, so we'd
have to keep that, and if we do that then we might as well add '-r/-E'
and a no-op '-e' just in case too....

Oddly the pdksh man page suggests *BSD echo has a '-e' option that makes
it behave much more like SuSv2's echo, though "our" echo is missing this
feature.....  Luckily '-e' is a no-op in ksh.

Of course SuSv2 goes on to say:


     It is not possible to use echo portably across all systems that are
     not XSI-conformant unless both -n (as the first argument) and
     escape sequences are omitted.

     The printf utility can be used portably to emulate any of the
     traditional behaviours of the echo utility as follows:

       * The XSI echo is equivalent to:

            printf "%b\n" "$*"

       * The BSD echo is equivalent to:

            if [ "X$1" = "X-n" ]
                    printf "%s" "$*"
                    printf "%s\n" "$*"

     New applications are encouraged to use printf instead of echo.

So maybe printf should be a builtin and 'echo' be a function or alias
that does the emulation as above.....

[[ Some people say /etc/inittab is the defining feature of AT&T UNIX,
but they're only trying to misdirect you from the real truth:  the
defining feature of AT&T UNIX is a sane 'echo' implementation!  :-) ]]

> The man page ought to list the builtins, there are some subtle
> differences.

It does.


     This section lists the builtin commands which are builtin because they
     need to perform some operation that can't be performed by a separate pro-
     cess. In addition to these, there are several other commands that may be
     builtin for efficiency (e.g.  printf(1), echo(1), test(1), etc).

>   eg what happens when a redirect fails (not checked
> that on netbsd - you need a device driver that rejects opens).

$ echo foo > /no/such/file
cannot create /no/such/file: directory nonexistent
$ echo $?
$ type echo
echo is a shell builtin

								Greg A. Woods

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