binary file, remove binary data ?

[Sver]

Is it possible to remove a character when  a file is open as binary ?

Null byte ?



'binary file example

 open "letter.txt" for binary as #myfile

 txt$ = "test"      '4 char

 print #myfile, txt$

 close #myfile



[Rod]

In a binary file you typically seek out a byte position and read or write it. You don’t just #myfile, txt$. So we need to see more of what you are trying to do.

[Sver]

When i print "test" to a binary file, then lenght is 4 characters.

When i print "te" to this binary file, it have to be 2 characters long.


Can i delete the last 2 bytes ?



'writeline text to line 5  ( textfile )



nomainwin

regel=5                       'print to line x

if regel=0 then wait   'not allowed

newword$="5"



open "letter.txt" for input as #i

   f$ =input$( #i, lof( #i))

close #i



'-----------------------------------------------------

' find startpos

regel=regel-1

start=0



for i=1 to regel

start=instr(f$, chr$(13), start+1)

next



'-------------------------------------------------------

' find endpos

regel=regel+1

eind=0



for i=1 to regel

eind=instr(f$, chr$(13), eind+1)

next



'-------------------------------------------------------

'how many lines

y=0

lengte=len(f$)



for q = 1 to lengte

a$=mid$(f$,q,1)

f=asc(a$)

if f=13 then y=y+1

next



y=y+1  'lines now

'----------------------------------------------

if regel>y then goto [addnewline]

'------------------------------------------

'string upto "line x"

if regel>1 then

 links$=left$(f$,start+1)   'incl enter

else

 links$=left$(f$,start)   'excl enter

end if

'--------------------------------------------------

'string after "line x"

rechts$=right$(f$,lengte-(eind-1))    'incl enter

'-----------------------------------------------

'total string

f$= links$+newword$+rechts$

'print

open "letter.txt" for output as #i

print #i, f$

close #i

'------------

'print "ready"

wait





[addnewline]

dif=regel-y

'---------

g=0

while g<dif

g=g+1

f$=f$+chr$(13)

wend

'--------------------------

f$=f$+newword$



open "letter.txt" for output as #i

print #i, f$

close #i

'------------

'print "ready"

wait





I works. but
I have to open for input, close and open for output and close.
In a binary file, i can read and write.
I can make a database with unlimeted field.

[Rod]

In a binary file the record pointer becomes king. So SEEK to where the two bytes are and overwrite new values.

But the concept of erasing data within a binary file is false, the file structure never changes bytes remain bytes until they are zeroed but remain in place or are overwritten with new values. But you don’t ever remove the two bytes.

So I think we have some wrong perceptions about binary files.