A console output question

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

Monks

I have written a perl script that reads a very large file line by line and processes it. I want to give the user some feedback, i.e. the current line. So I want to write to the console something like:

Current line is: 31721
[download]

I could do it with a print statement, but this produces a new line for each update. Is it possible to overwrite the previous line, i.e. 31721 becomes 31722 and gives the illusion of a counter and looks much neater?

Thanks,

____________
Arun

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Re: A console output question by Chmrr (Vicar) on Jun 18, 2002 at 10:47 UTC
Use `print "Current line is: $line\r"` or some varient thereof. \r moves the 'cursor' to the start of the line, without moving down a line. You will need to turn buffering off (`$\|++`) for this to work. perl -pe '"I lo`+$^X$\"$]!$/"=~m%(.)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'	[reply] [d/l] [select]
Re: A console output question by greenFox (Vicar) on Jun 18, 2002 at 10:51 UTC
See this How to UPDATE rather than append to STDOUT? node. -- my $chainsaw = 'Perl';	[reply]
Re: A console output question by demerphq (Chancellor) on Jun 18, 2002 at 11:30 UTC
I like to use the following: `use Tie::Cycle; tie my $spinner, 'Tie::Cycle', ["\r-","\r\\","\r\|","\r//"]; my $spin_every=10; while (<>) { print $spinner unless $. % $spin_every; # yada-yada-yada }` [download] The result is a spinning line. Excellent for indicating the program is still alive. The use of mod prevents the output fom happening so often that printing slows the script down noticibly. Yves / DeMerphq --- Writing a good benchmark isnt as easy as it might look.	[reply] [d/l]
Re: A console output question by strat (Canon) on Jun 18, 2002 at 11:18 UTC
Btw: with a while(<...>) - loop, you can find out about the current line by reading the content of the special Variable $. as long as the Filehandle is still opened. But if you change the variable $/ , $. will give you the number of read blocks (what a block is, is said in $/ ). Best regards, perl -e "s>>F>e=>y)\martinF)stronat)=>print,print v8.8.8.32.11.32"	[reply]


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