Re: getchar implementation without GNUishms

On 26.03.2025 05:16, Arti F. Idiot wrote:

On 3/25/25 7:10 AM, Janis Papanagnou wrote:

On 25.03.2025 10:51, anthk wrote:

Hello the guy from https://luxferre.top and gopher://hoi.st
has pretty interesting stuff, such as
>
[ shell specific or other tries to emulate some getchar function ]
>
Could it be possible to implement a true portable getchar?

>
Those who think that getchar is a useful function may implement that
natively in Awk. (It avoids external dependencies and all the issues
that the posted/quoted code has made obvious.)

 
I know you can iterate over input strings a character at a time in AWK
but I don't think you can read a single character from stdin without
also providing a newline via ENTER, which is perhaps what the OP was
actually wanting to do?

I don't know. - When I read 'getchar' I associated a character oriented
function like awk's 'getline'. That would mean not reading from stdin
with some I/O buffered return-terminated input but just processing the
data as Awk would read its input from stdin or using 'getline' would.
You need to maintain some state, though; here the actual read in line
which acts like a buffer in buffered OS reads.

What I associated was actually something like

    function getchar ()
    {
        if (_pos >= _len) {
            do {
                if ((getline _line) <=0)
                    return  ""
            }
            while (!(_len = length (_line)))
            _pos = 0
        }
        return  substr (_line, ++_pos, 1)
    }

used in contexts like

    BEGIN {
        # RS = "$^"
        while (c = getchar())
            print ">" c "<"
    }

where the commented RS assignment could be activated in case you wanted
to also read the newline characters, or, without it, to just read in
the payload data of a line (or record). The necessary state information
is stored in those variables that are named with a leading underscore.

As said it's native Awk code without those dependencies on OS, on tools,
or on specific non-standard flags of tools.

(But as indicated in my previous response, I don't have any need for a
function like that. Maybe others do, don't know.)

Janis

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