On 2022-08-09, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
> Thanks to process substitution in newer shells I can write, e.g.,
> strings <( zcat file.gz ) | ...
>
> I am wondering, though, whether there's a reason why 'strings' is
> not defined to support (additionally) filter calling semantics
> ...(binary stream)... | strings | ...(text stream)...

Think that it's not there because POSIX doesn't require it, I checked
POSIX. In POSIX, I found this:

"If the first argument is '-', the results are unspecified."

Aha, so implementations of strings are permitted (encouraged, I might
say) to support standard in reading via the - convention.

The wording probably exists because some strings implementations
do and some do not?

The strings from GNU Bintutils 2.30 does handle stdin---and does not
like the - argument; go figure.

Deliberate use of cat;

$ cat /proc/self/environ | strings | head -4
CLUTTER_IM_MODULE=xim
XDG_MENU_PREFIX=gnome-
LANG=en_CA.UTF-8
DISPLAY=:1

What "strings" are you looking at? Maybe it handles - as a way of
specifying stdin. (Still, if you want that in a portable
script, PITA).

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal

On Tue, 9 Aug 2022 20:15:59 -0000 (UTC)
Kaz Kylheku <480-992-1380@kylheku.com> wrote:
> On 2022-08-09, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
> > Thanks to process substitution in newer shells I can write, e.g.,
> > strings <( zcat file.gz ) | ...
> >
> > I am wondering, though, whether there's a reason why 'strings' is
> > not defined to support (additionally) filter calling semantics
> > ...(binary stream)... | strings | ...(text stream)...
>
> Think that it's not there because POSIX doesn't require it, I checked
> POSIX. In POSIX, I found this:
>
> "If the first argument is '-', the results are unspecified."
>
> Aha, so implementations of strings are permitted (encouraged, I might
> say) to support standard in reading via the - convention.

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/strings.html :

strings [-a] [-t format] [-n number] [file...]
[...]

INPUT FILES
The input files named by the utility arguments or the standard
input shall be regular files of any format.

So a file argument is optional and it explicitly says that reading
from standard input is allowed. But I'm not sure what it means for
the standard input to be a regular file.

> The wording probably exists because some strings implementations
> do and some do not?
>
> The strings from GNU Bintutils 2.30 does handle stdin---and does not
> like the - argument; go figure.

[...]

--
vlaho.ninja/prog

On 10.08.2022 10:27, Spiros Bousbouras wrote:
>
> https://pubs.opengroup.org/onlinepubs/9699919799/utilities/strings.html :
>
> strings [-a] [-t format] [-n number] [file...]

I was fooled by my man page; the POSIX syntax is clear here.

Janis

Kaz Kylheku wrote:

> On 2022-08-09, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
>>
>> I am wondering, though, whether there's a reason why 'strings' is
>> not defined to support (additionally) filter calling semantics
>> ...(binary stream)... | strings | ...(text stream)...
>
> Think that it's not there because POSIX doesn't require it, I checked
> POSIX. In POSIX, I found this:
>
> "If the first argument is '-', the results are unspecified."
>
> Aha, so implementations of strings are permitted (encouraged, I might
> say) to support standard in reading via the - convention.

That text is there because with some versions of strings, "strings -"
means the same as "strings -a".

If you give an operand of '-' that isn't the first argument, e.g.
"strings -- -", then POSIX actually requires it to read from a
file named '-'. However, this doesn't match existing practice so
it is probably an oversight in POSIX (my guess, as a result of the
"first argument is '-'" text being there).

Anyway, the text most relevant to Janis's question is in the OPERANDS
section:

The following operand shall be supported:

file
A pathname of a regular file to be used as input. If no file
operand is specified, the strings utility shall read from the
standard input.

--
Geoff Clare <netnews@gclare.org.uk>

On 2022-08-10, Geoff Clare <geoff@clare.See-My-Signature.invalid> wrote:

> file
> A pathname of a regular file to be used as input. If no file
> operand is specified, the strings utility shall read from the
> standard input.

As indeed it has been doing since it appeared in 3.0BSD in 1980.

--
Christian "naddy" Weisgerber naddy@mips.inka.de