perl How to read command line argument as if it's file content

Question

I have a function that takes in filename and prints the content of the file

#test.pl
while (<>) {
    print $_;
}
exit(0);

I want to run this on the command line except instead of a filename I want to use the actual content as parameter without changing the script, similarly to an anonymous FIFO (e.g. "<(...)" operator in shell) to substitute a filename string with it's content?

It's not clear what you are asking. <> can already read from stdin (btw, you should be using <<>>). What do you mean when you say "I have a function" ? — jhnc
– jhnc, Commented Apr 17, 2019 at 1:51
If you provide a filename of '-' then perl will interpret that as "read from STDIN", however that's also the default behaviour if you don't supply a filename at all. In the bash shell you can do something like this: test.pl <<<"some content here which bash will supply on STDIN" — Grant McLean
– Grant McLean, Commented Apr 17, 2019 at 4:10

ikegami · Accepted Answer · 2019-04-17 06:35:04Z

2

This is a shell question, but you didn't specify which shell.

sh

It's simplest to simply pass the data to STDIN instead.

printf 'foo bar' | test.pl

printf 'foo\nbar\n' | test.pl

test.pl <<'.'
foo
bar
.

bash

In addition to the solutions for sh, you can also use the following:

test.pl <<<'foo bar'

test.pl <<<$'foo\nbar\n'

test.pl <( printf 'foo\nbar\n' )

The last one avoids using STDIN. This is (internally) more complicated than the other solutions, but it allows you to pass multiple "virtual files".

edited Apr 17, 2019 at 6:35

answered Apr 17, 2019 at 6:19

ikegami

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4 Comments

kkawabat Over a year ago

Thank you that worked. However this solution does not work when there are multiple arguments to the script. Is it possible to pass the data to STDIN for only the last param?

ikegami Over a year ago

As the answer mentions, the last one does.

kkawabat Over a year ago

I apologize so for the final example if I want to use multiple args I would just do test.pl ARG1 <( printf 'foo\nbar\n' ) where <( printf 'foo\nbar\n' ) is ARG2?

ikegami Over a year ago

Yes. For the others solutions, you can only do that if the other args are options (test.pl --foo=bar <<<'foo bar' is ok, but test.pl' file.txt file2.txt <<<'foo bar' is not ok)

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