perl one-liner doesn't autochomp input

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

Hello

I read this great article about Perl Command-Line Options, printed it and had it on my desk. Today I needed to accomplish a simple task: having the output of an ls -1 (that's "minus one") and output a single line with all the filenames separated by ":". In other days I would have written it this way:

ls -1 | perl -e '@_=<>;chomp@_;print join":",@_'

and in fact it just works. But after reading the article, and in particular this:

Using -l and giving it no value has two effects. Firstly, it automatically chomps the input record, and secondly, it sets $\ equal to $/. If you give -l an octal number (and unlike -0 it doesn't accept hex numbers) it sets $\ to the character represented by that number and also turns on auto-chomping.

I expected I could write my one-liner this way:

ls -1 | perl -le 'print join ":",<>'

but it actually doesn't what I expected. Could anybody explain where I am doing wrong?

Thanks a lot

Ciao!
--bronto

The very nature of Perl to be like natural language--inconsistant and full of dwim and special cases--makes it impossible to know it all without simply memorizing the documentation (which is not complete or totally correct anyway).
--John M. Dlugosz

Comment on perl one-liner doesn't autochomp input Select or Download Code

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Re: perl one-liner doesn't autochomp input by broquaint (Abbot) on Sep 07, 2004 at 10:05 UTC
The first effect of using `-l` is better documented in `perlrun` `It has two separate effects. First, it automatically chomps $/ (the input record separator) when used with -n or -p.` Not taking full advantage of perl's you could always write your one-liner like this `ls -1 \| perl -le 'print join ":", map /(.*)$/, <>'` [download] HTH `_________ broquaint`	[reply] [d/l]
Re: perl one-liner doesn't autochomp input by Anonymous Monk on Sep 07, 2004 at 10:13 UTC
`$ ls -1 \| perl -l72pe1` [download]	[reply] [d/l]
Re^2: perl one-liner doesn't autochomp input by bronto (Priest) on Sep 07, 2004 at 10:20 UTC
Oh, damn! How I would like to front-page this! So GREAT! Update: apart that it adds a trailing ":", which I don't like to be there `:-(` Update: so do also tachyon's and keszler's solutions: the trailing ":" should not be there Ciao! `--bronto` The very nature of Perl to be like natural language--inconsistant and full of dwim and special cases--makes it impossible to know it all without simply memorizing the documentation (which is not complete or totally correct anyway). --John M. Dlugosz	[reply] [d/l]
Re^3: perl one-liner doesn't autochomp input by tachyon (Chancellor) on Sep 07, 2004 at 12:40 UTC
`ls\|xargs\|perl -pe 'y/ /:/'` fixes the trailing ':' issue as xargs converts the ls output into a nice space separated stream.	[reply] [d/l]
Re^4: perl one-liner doesn't autochomp input by halley (Prior) on Sep 07, 2004 at 13:39 UTC
Re^5: perl one-liner doesn't autochomp input by sintadil (Pilgrim) on Sep 07, 2004 at 17:51 UTC
Re^4: perl one-liner doesn't autochomp input by Jasper (Chaplain) on Sep 07, 2004 at 13:39 UTC
Re^5: perl one-liner doesn't autochomp input by abclex (Monk) on Sep 07, 2004 at 14:16 UTC
Re^2: perl one-liner doesn't autochomp input by jbullock35 (Hermit) on Sep 07, 2004 at 13:02 UTC
`$ ls \| perl -l72pe1` This works and seems equivalent to `$ ls \| perl -l72pe "{}"` But I don't understand the role of "1" (or digits in general) at the end of the command line, and I can't find any explanation in `perlrun`. I thought that they might affect the way that arguments are processed, but that doesn't seem right. Can someone clarify? Thanks, --John	[reply] [d/l] [select]
Re^3: perl one-liner doesn't autochomp input by Aristotle (Chancellor) on Sep 07, 2004 at 18:16 UTC
The 1 is there because you have to supply some Perl code to `-e`, but in this case you don't care to do anything, you just want the side effects of the other switches. Using a 1 by itself as your "script" is just like having `1;` on a line by itself in a script — it does nothing. This can be used for such funny command lines as `perl -please textfile # print the contents of the textfile perl -deal # fire up the debugger for interactive fiddling` [download] These are equivalent to `perl -p -l -e '"ase"' textfile perl -d -e '"al"'` [download] where you simply have a string on a line by itself as the only statement in your "code", resulting in a no-op. Makeshifts last the longest.	[reply] [d/l] [select]
Re^3: perl one-liner doesn't autochomp input by Anonymous Monk on Sep 07, 2004 at 13:05 UTC
`perl -neprint /etc/passwd` [download]	[reply] [d/l]
Re: perl one-liner doesn't autochomp input by tachyon (Chancellor) on Sep 07, 2004 at 10:42 UTC
`ls \| perl -pe 's/\n/:/'` Removed redundant -n from perl Sidhekin notes that -np == -p ; also removed -1 from ls because you don't need it either.	[reply] [d/l]
Re: perl one-liner doesn't autochomp input by keszler (Priest) on Sep 07, 2004 at 11:06 UTC
`ls -1 \| perl -l0 -ne 'print $_, ":"'` [download] works. In the 5.6.1 and 5.8.4 versions of perlrun, the -l switch is documented to auto-chomp only when used with the -n or -p switches. You need both the chomp and a null $\.	[reply] [d/l]
Re: perl one-liner doesn't autochomp input by Aristotle (Chancellor) on Sep 07, 2004 at 18:04 UTC
Offtopic, but a solution to the ultimate problem: `perl -le'print join ":", glob ""'` [download] Or if you let the shell do the work for you `perl -le'print join ":", @ARGV' ` [download] Or maybe `perl -le'$,=":";print<>' perl -le'$,=":";print@ARGV' ` [download] Makeshifts last the longest.	[reply] [d/l] [select]


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