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Re: How to read first and last line of an ascii file FAST [message #72409 is a reply to message #72335]

Tue, 31 August 2010 09:08

R.Bauer
Messages: 1424
Registered: November 1998

Senior Member

Am 29.08.2010 18:32, schrieb Heinz Stege:
> On Sun, 29 Aug 2010 08:32:15 -0700 (PDT), ahs wrote:
>
>> Hello group,
>>
>> My data is stored in a bunch of ascii files, each 5-10MB big. Each
>> line represent a sample with a timestamp. I would like to analyse all
>> my files by reading the timestamp from the first and last line of
>> every file. Getting the timestamp from the last line is the issue
>> here. Right now I'm doing it like
>>
>> readf, fid, firstline
>> nlines = FILE_LINES(fnames[i])
>> skip_lun, fid, nlines-2, /LINES
>> readf, fid, lastline
>>

did you tried reading the file in one string array of len file_lines

IDL> f = "example.txt"
IDL> n = file_lines(f)
IDL> data = make_array(n,/string)
IDL> openr, lun, /get_lun, f
IDL> readf, lun , data
IDL> free_lun, lun
IDL> print, data[n-1]

that needs 0.05 seconds to get that information

Reimar

>> skip_lun is really slow when the files are big and numerous. Does
>> anyone have a tip of I could do this faster? Is there a way to
>> directly point to the end of the file minus one line?
>>
>> regards,
>> Agnar

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[Message index]

		Re: How to read first and last line of an ascii file FAST By: Jeremy Bailin on Sun, 29 August 2010 18:27
		Re: How to read first and last line of an ascii file FAST By: Heinz Stege on Sun, 29 August 2010 09:32
		Re: How to read first and last line of an ascii file FAST By: agnarhs on Fri, 03 September 2010 02:56
		Re: How to read first and last line of an ascii file FAST By: R.Bauer on Tue, 31 August 2010 09:08

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