Hi Yary (and Todd),
Thank you both for your responses. Yary, the problem seems to be with
"get". I can change 'while' to 'for' below, but using 'get' raku/perl6
actually returns fewer lines with "for" than it did with "while":
[1]mydir$ cat testthis_abc_def.txt
a
b
c
d
e
f
[2]mydir$ perl6 -e '.say while $_ = $*IN.get;' < testthis_abc_def.txt
a
b
c
[3]mydir$ perl6 -e '.say for $_ = $*IN.get;' < testthis_abc_def.txt
a
I assumed 'get' was looking at EOF but that's incorrect--apparently
'get' acts more like a glorified call to lines[0], reading one line of
an input file and then stopping. I can read my whole test file by
explicitly testing for EOF (note the redeclaration of $*IN below).
Otherwise, my best course of action is replacing 'get' with 'lines',
and using either 'while' or 'for' ('.say for $*IN.lines;' replicates
'cat' behavior the best):
[4]mydir$ perl6 -e 'while not($*IN.eof) -> {$*IN.get.say };' <
testthis_abc_def.txt
a
b
c
d
e
f
[5]mydir$ perl6 -e '.say while $_ =$*IN.lines;' < testthis_abc_def.txt
(a b c d e f)
[6]mydir$ perl6 -e '.say for $_ = $*IN.lines;' < testthis_abc_def.txt
(a b c d e f)
[7]mydir$ perl6 -e '.say for $*IN.lines;' < testthis_abc_def.txt
a
b
c
d
e
f
HTH, Bill.
On Sat, Jan 18, 2020 at 5:55 PM yary <not....@gmail.com> wrote:
>
> "while" is the wrong looping construct for going over file lines, and that's
> across a great many computer languages. It will stop when it encounters a
> false line- typically an empty line or '0'
>
> Try "for"
>
> -y
>
>
> On Sat, Jan 18, 2020 at 4:45 PM William Michels <w...@caa.columbia.edu> wrote:
>>
>> Hello All,
>>
>> I've been reviewing literature that discusses using raku/perl6 as a
>> replacement for common unix utilities. One important unix utility is
>> "cat". I looked at docs/blogs and found a recommendation to use "$*IN"
>> along with "slurp" (references at bottom). Using a seven-line test
>> file "testthis_abc_def.txt" below (1), the recommended "slurp" code
>> works as expected (2).
>>
>> However, another recommendation to use "$*IN" along with the "get"
>> method fails when a blank line is encountered, only returning
>> truncated output (3). I tried correcting truncated output seen with
>> "get" by playing with the command-line arguments "-ne" (4) and "-pe"
>> (5), but only ended up mangling output even further.
>>
>> Can "get" be used in when writing raku/perl6 replacement code for "cat"?
>>
>> Any advice appreciated,
>>
>> Bill.
>>
>>
>> [1]mydir$ cat testthis_abc_def.txt
>> a
>> b
>> c
>>
>> d
>> e
>> f
>> [2]mydir$ perl6 -e 'say $*IN.slurp;' < testthis_abc_def.txt
>> a
>> b
>> c
>>
>> d
>> e
>> f
>>
>> [3]mydir$ perl6 -e '.say while $_ = $*IN.get;' < testthis_abc_def.txt
>> a
>> b
>> c
>> [4]mydir$ perl6 -ne '.say while $_ = $*IN.get;' < testthis_abc_def.txt
>> b
>> c
>> e
>> f
>> [5]mydir$ perl6 -pe '.say while $_ = $*IN.get;' < testthis_abc_def.txt
>> b
>> c
>>
>> e
>> f
>> (Mu)
>> [6]mydir$
>>
>>
>> REFERENCES:
>> 1. https://docs.raku.org/routine/slurp
>> 2. https://docs.raku.org/routine/get
>> 3. https://andrewshitov.com/2019/09/09/the-cat-utility-written-in-perl-6/
>> 4.
>> https://stackoverflow.com/questions/52597984/catching-exception-of-a-shell-command-in-perl-6
