Linux file handle not working

pvfki has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I am trying to run a perl command through linux console using filehandle ($_ sign) in order to indicate a file to use when running the command. The commands from the code snippet below are from https://metacpan.org/pod/ntheory

For example, I have the following number in input.txt: 147416345806550029415781910597841 Running with Windows:

>perl -Mntheory=:all -nE "chomp; say is_prime($_);" input.txt
1
>perl -Mntheory=:all -nE "chomp; say length($_);" input.txt
33
[download]

Running on Linux however I get:

>perl -Mntheory=:all -nE "chomp; say is_prime($_);" input.txt
Parameter 'inputtxt' must be a positive integer at -e line 1, <> line 
+1.
>perl -Mntheory=:all -nE "chomp; say length($_);" input.txt
Parameter 'inputtxt' must be a positive integer at -e line 1, <> line 
+1.
[download]

Does anyone know how to fix this? I'm not sure how perl (shell) via Linux works? How do I get the same output as Windows? Thanks for help!

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Re: Linux file handle not working by shmem (Chancellor) on Jan 16, 2020 at 01:36 UTC
The shell quoting rules are different between Windows and Linux/UNIX. Within double quotes (") the `$` sign is significant to the Linux/UNIX shell. Try: `>perl -Mntheory=:all -nE 'chomp; say is_prime($_);' input.txt` [download] The argument for the `-e` flag is surrounded with " on Windows, but with ' on Linux/UNIX. Quoting rules therefore are different in the body of the script provided via `-e`, which led iirc to the `q()` family of operators (see perlop) update: the `_` identifier is set in the shell to the last argument of the previous command, so `$_` is set to `input.txt` which is interpolated into the program string passed to perl via `-e` as the expression of concatenation of two barewords: `qwurx [shmem] ~> perl -E "say '$_'" foo.bar qwurx [shmem] ~> perl -E "say '$_'" foo.bar foo.bar qwurx [shmem] ~> perl -E "say $_" foo.bar foobar` [download] This is a dangerous thing, if the last argument of the previous line happens to contain metacharacters, e.g. qwurx [shmem] ~> echo '`ls -l /dev/null`' `ls -l /dev/null` qwurx [shmem] ~> perl -E "say $_" crw-rw-rw- 1 root root 1, 3 Nov 27 11:02 /dev/null qwurx [shmem] ~> perl -MO=Deparse -E "say $_" use feature 'current_sub', 'evalbytes', 'fc', 'say', 'state', 'switch' +, 'unicode_strings', 'unicode_eval'; say say(say(`ls -l /dev/null`)); -e syntax OK [download] so don't do that. perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'	[reply] [d/l] [select]
Re: Linux file handle not working by 1nickt (Canon) on Jan 16, 2020 at 01:33 UTC
Hi, Works for me with Math::Prime::Util v.073 on MacOS with Perl 5.30.1 and on Ubuntu with Perl 5.28.1 : `$ echo 147416345806550029415781910597841 > input.txt` [download] `$ perl -Mstrict -Mntheory=:all -wnE 'chomp; say is_prime($_);' input.t +xt 1` [download] `$ perl -Mstrict -Mntheory=:all -wnE 'chomp; say length($_);' input.txt 33` [download] Hope this helps! The way forward always starts with a minimal test.	[reply] [d/l] [select]

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