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Forum Index : Microcontroller and PC projects : Using SEEK
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Chrisk Senior Member  Joined: 21/12/2014 Location: AustraliaPosts: 121 |
Hi all I am trying to print some lines from a file using the seek command. I can get it to print from the start of the file using forward.bas but I really want it to print from the bottom up. I have tried manipulating with the value "y" but keep getting an error. Any ideas? ps I found that this program runs forward in the old version of MMBasic but not in the latest. Chrisk forward.zip Originally placed this in Windmills by accident  |
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| twofingers Guru  Joined: 02/06/2014 Location: GermanyPosts: 1245 |
Hi, Which firmware version and which hardware are you using? It should work with the latest versions for the Picomite (=>A25). Regards Michael EDIT: i=0 ???? [8] Seek #1, i 'Points to start of data location Error : 0 is invalid (valid is 1 to 2147483647) Try i=1  Edited 2023-03-26 12:01 by twofingers causality ≠ correlation ≠ coincidence |
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| Chrisk Senior Member Joined: 21/12/2014 Location: AustraliaPosts: 121 |
Hi Twofingers I have tried out your suggestion with my Windows MMBasic Ver 5.05.05 and it works. Thanks for that. The old DOS MMBasic Ver 4.5 worked with i = 0. With i = 1 the program did not print the first character in line 1. I use the Micromite plus 64. The program (forward) works on the MM+64 with i = 0 which I will change to i = 1 but I would like to have it read in reverse line order. I use DOS MMBasic to verify parts of my program of which this is only a part. Thank you Chrisk |
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| twofingers Guru Joined: 02/06/2014 Location: GermanyPosts: 1245 |
You can customize your program by using "mm.device$" to query the hardware used. If you're reading your data forward and from the beginning of the file, you don't need to use Seek. You only need Seek to read backwards. causality ≠ correlation ≠ coincidence |
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| Chrisk Senior Member Joined: 21/12/2014 Location: AustraliaPosts: 121 |
Hi again I am not sure I expressed myself clearly enough. I am reading the file gtest2 and sending each line to a LCD display. Currently "forward.bas" displays the line 02-03-20 08:12 first. I am not sure how a program can read the line 16-09-20 07:45 which is actually the last line but display it first. 'forward.bas ' Displays stored data in gtest2.txx to a line in an LCD display i = 1 OPEN Prevd$ FOR RANDOM AS #1 y = LOF(#1) 'Determines number of bytes in file print y seek #1, i 'Points to start of data location DO LINE INPUT #1, dat$ print dat$ pause 500 LOOP UNTIL EOF(#1) CLOSE #1 end 02-03-20 08:12 04-04-20 09:23 06-05-20 10:45 08-06-20 12:27 12-07-20 08:12 14-08-20 09:23 16-09-20 07:45 Chrisk |
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| Chrisk Senior Member Joined: 21/12/2014 Location: AustraliaPosts: 121 |
Obviously from the look of the post I don't know what I am doing in regard to posting correctly. Should have previewed first. Sorry about that. Chrisk |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6102 |
Are the liens equal length? how many lines are expected - can they be loaded into an array if memory is sufficient? Jim VK7JH MMedit MMBasic Help |
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jirsoft Guru Joined: 18/09/2020 Location: Czech RepublicPosts: 532 |
If the lines really have the same length (15 bytes?), you can calculate number of lines from file size: lineLen = 15 'for example, need to be properly set fileSize = MM.INFO(FILESIZE file$) 'get file size numLines = fileSize / lineLen 'not needed, just for information (progress bar?) actLine = fileSize - lineLen 'pointer to last line then you can seek SEEK #1, actLine 'set file pointer to actual line INC actLine, -lineLen 'decrease pointer, go one line back Edited 2023-03-27 18:09 by jirsoft Jiri Napoleon Commander and SimplEd for CMM2 (GitHub), CMM2.fun |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6102 |
'reverse listing Prevd$ = "C:\Users\Jim\Documents\myapps\maximite\apps - Copy\listing.txt" linelength = 18 ' includes <CRLF> OPEN Prevd$ FOR RANDOM AS #1 y = LOF(#1) 'Determines number of bytes in file PRINT "Y = ";y y = y - linelength + 1 FOR i = y TO 1 STEP -linelength SEEK #1, i 'Points to start of data location dat$ = INPUT$( linelength-2,#1) PRINT dat$ NEXT i CLOSE #1 You often have to experiment with line length due to different line endings. Make sure that your data doesn't have the occasional TAB. That can upset the line length. Jim VK7JH MMedit MMBasic Help |
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| Chrisk Senior Member Joined: 21/12/2014 Location: AustraliaPosts: 121 |
Thank you guys It's working as I require whilst testing it with MMBasic. No need to implement in micro at my daughters place. I did have to change the line y = y - linelength + 1 to y = y - linelength - 1 as it was cutting off the first 2 characters of each line. Not sure why. Jim What is the significance of the ; in the line PRINT "Y = ";y It doesn't appear to change anything whether it is there or not. To you all  Chrisk |
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| Chrisk Senior Member Joined: 21/12/2014 Location: AustraliaPosts: 121 |
Back again Apologies to Jim  On another set of data for the data file I found I had to change the line back to what you had written i.e. y = y - linelength + 1 Chrisk |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6102 |
From the help files: I prefer to use the ; rather than nothing. It makes the line of code clearer (to me). It all depends if your data ends with <CRLF>, no end of line or two <CRLF> pairs. Text files often end up with an extra blank line at the end. Your file that needed y = y - linelength - 1 didn't have any end-of-line. The safe way is to fetch more than required and search the string looking for the end-of-line. Then use that as the starting point. Jim VK7JH MMedit MMBasic Help |
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| Chrisk Senior Member Joined: 21/12/2014 Location: AustraliaPosts: 121 |
Thanks Jim much appreciated  ChrisK |
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