Writing/Reading Files- What's going on?

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KenGames

11

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Joined: 22nd Sep 2013

Location: United States

Posted: 6th Jun 2015 01:33

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I've had a bit of experience in writing and reading files before, I used to do it all the time in C# XNA, but now in DBPro(which is much easier btw) I've come across a strange issue. Assuming the directory is the standard project directory, this code sample when run fails to write to the file. If I open the file with notepad it is empty. What am I missing here???? -It seems simple enough.

+ Code Snippet

Make File "TestFile.dat"
Open To Write 1, "TestFile.dat"

Write String 1, "Hello File World"
Wait 1000

Close File 1
Wait 1000

Open to Read 1, "TestFile.dat"
Read String 1, string$
Print "Contents:" + string$

Wait 5000
End

In the sample above, it creates and writes to a file. Then displays a text holding the contents of the file(which results in empty).

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WickedX

16

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Joined: 8th Feb 2009

Location: A Mile High

Posted: 6th Jun 2015 03:14 Edited at: 6th Jun 2015 03:21

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Make File is a useless function. All it does is create an empty file. Open file will create the file if it does not already exist. Since you have created the file with Make File it cannot be accessed to write. Try this instead.

+ Code Snippet

`make file "TestFile.dat"
if (file exist("TestFile.dat"))
   delete file "TestFile.dat"
endif

open to write 1, "TestFile.dat"

write string 1, "Hello File World"

close file 1
wait 2000

open to read 1, "TestFile.dat"
read string 1, string$
print "Contents: " + string$

close file 1
wait 5000
end

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KenGames

11

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Joined: 22nd Sep 2013

Location: United States

Posted: 6th Jun 2015 03:26

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Ah, thanks. Would not have guessed that Make File was not necessary.

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Ortu

DBPro Master

17

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Joined: 21st Nov 2007

Location: Austin, TX

Posted: 6th Jun 2015 05:56

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also note that open to write will silently fail without error if the file already exists, it will not append. if you want to append you will need to read it, delete it, open to write and write it back out again along with anything new

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Attila

FPSC Reloaded TGC Backer

20

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Joined: 17th Aug 2004

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Posted: 6th Jun 2015 14:38 Edited at: 12th Jun 2015 00:28

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The function append_to_file will append a line to an existing file. If the file does not exist it will create a new file.

remstart 
---------------------------------------------------------------------------------
(C) 2015, Atilla

Test for function append_to file
---------------------------------------------------------------------------------
remend

set window on
set display mode 800,600,32
set window size 800,600
cls

append_to_file(\"test.txt\",1,\"My First Record\")
append_to_file(\"test.txt\",1,\"My 2nd Record\")

for h=3 to 10
    append_to_file(\"test.txt\",1,\"My \"+str$(h)+\"th Record\")
next h

`suspend for key
end

`---------------------------------------------------------------------------------
function append_to_file(Filename$,FileNumber,Text$)
`    
` (C) 2015 - Attila
`
` The function appends a line at the end of a file. If the file does not
` exist it will create a new file
`---------------------------------------------------------------------------------
    if file exist(Filename$) = 0
        open to write FileNumber, Filename$
        write string FileNumber, Text$
        close file FileNumber
    else
        if file exist(FileName$+\"_save\") then delete file FileName$+\"_save\"
        rename file FileName$, FileName$+\"_save\"
        FNr2=FileNumber+1
        open to read FNr2, FileName$+\"_save\"
        open to write FileNumber, Filename$
        while not file end(FNr2)
            read string FNr2, Tmp$
            write string FileNumber, Tmp$
        endwhile
        write string  FileNumber, Text$
        close file FileNumber
        close file FNr2
        if file exist(FileName$+\"_save\") then delete file FileName$+\"_save\"
    endif
endfunction

+ Code Snippet

remstart 
---------------------------------------------------------------------------------
(C) 2015, Atilla

Test for function append_to file
---------------------------------------------------------------------------------
remend

set window on
set display mode 800,600,32
set window size 800,600
cls

append_to_file(\"test.txt\",1,\"My First Record\")
append_to_file(\"test.txt\",1,\"My 2nd Record\")

for h=3 to 10
    append_to_file(\"test.txt\",1,\"My \"+str$(h)+\"th Record\")
next h

`suspend for key
end

`---------------------------------------------------------------------------------
function append_to_file(Filename$,FileNumber,Text$)
`    
` (C) 2015 - Attila
`
` The function appends a line at the end of a file. If the file does not
` exist it will create a new file
`---------------------------------------------------------------------------------
    if file exist(Filename$) = 0
        open to write FileNumber, Filename$
        write string FileNumber, Text$
        close file FileNumber
    else
        if file exist(FileName$+\"_save\") then delete file FileName$+\"_save\"
        rename file FileName$, FileName$+\"_save\"
        FNr2=FileNumber+1
        open to read FNr2, FileName$+\"_save\"
        open to write FileNumber, Filename$
        while not file end(FNr2)
            read string FNr2, Tmp$
            write string FileNumber, Tmp$
        endwhile
        write string  FileNumber, Text$
        close file FileNumber
        close file FNr2
        if file exist(FileName$+\"_save\") then delete file FileName$+\"_save\"
    endif
endfunction

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