perl one-liner

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

Replies are listed 'Best First'.
Re: perl one-liner by Kanji (Parson) on Jun 22, 2005 at 17:02 UTC
`perl -0777 -i -nle 'print q{hello}' test.pl` ...but as others have pointed out, it's much easier to handle this sort of thing with shell redirection. --k.	[reply] [d/l]
Re^2: perl one-liner by mojobo (Initiate) on Jun 22, 2005 at 21:22 UTC
hi guys, actually shell redirection is what i have been doing in the past (without perl), but i wanted to have a one-liner that can be called externally. The basic idea is to automate editing a file with different access permissions than the user, via sudo, and not have to chown the file first to the user.. i can already edit a file if there is content in the file, without using shell redirection, using a perl one-liner like this: `perl -i -ne 'print unless 1 .. 100; print q{testing} if$.==1' somefile` [download] of course this doesn't truncate the file, which is what i was interested in attempting..	[reply] [d/l]
Re^2: perl one-liner by mojobo (Initiate) on Jun 22, 2005 at 21:25 UTC
Hi Kanji, i didn't see your reply when i was posting mine.. thanks! that's perfect.. thanks to everyone for their help.	[reply]
Re: perl one-liner by tlm (Prior) on Jun 22, 2005 at 16:55 UTC
`$1` doesn't do what I think you think it does. In Perl, what you're calling `$1` is called `$ARGV[ 0 ]`. Perl's `$1` is used to refer to the first of a regular expression's "captured" matches. See perlretut and perlre. Anyway, if I'm guessing correctly what you have in mind, and I am the happy beneficiary of a typical Unix shell, and I want to use perl to do this, I'd do: `perl -le 'print q{hello)' > test.pl` [download] the lowliest monk	[reply] [d/l]
Re: perl one-liner by friedo (Prior) on Jun 22, 2005 at 16:53 UTC
So in other words, you just want to overwrite a file? Why not just open it with '>'?	[reply]
Re: perl one-liner by Transient (Hermit) on Jun 22, 2005 at 16:53 UTC
Why do you need perl for that? echo "hello" > file (and it works on Win32 and UNIX!) Unless I'm misreading the question... Update: If this is just an exercise to use truncate... `perl -i -e 'truncate <>,0; print "HELLO";' mytest` [download] Update: trying to figure out the right way to do this... Update^3: `perl -i -pe 'truncate $ARGV[0], 0; print "Hello"; last' test.pl` do note that if the file doesn't exist or is empty already, this won't work.	[reply] [d/l] [select]