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how to insert and delete characters in the middle of file


 
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# 1  
Old 10-04-2004
Question how to insert and delete characters in the middle of file

I have a problem that I want to insert and delete some chars in the middle of a file. fopen() and fdopen() just allow to append at the end.

Is there any simple method or existing library that allow these actions? Thanks in advance.Smilie
# 2  
Old 10-05-2004
Isn't there any other clever and efficient way to do that?
# 3  
Old 10-05-2004
Driver gave you the clever efficient way. Smilie
# 4  
Old 10-06-2004
anyway, thanks veru much Smilie
# 5  
Old 10-07-2004
If you have the memory, you might want to read the whole file into memory, manipulate it there and then dump the results back to disk.

That could be faster depending on a number of factors e.g number of search operations, insert/delete operations, disk performance or size of file.
# 6  
Old 10-07-2004
Quote:
If you have the memory, you might want to read the whole file into memory, manipulate it there and then dump the results back to disk.

That could be faster depending on a number of factors e.g number of search operations, insert/delete operations, disk performance or size of file.
But this method of loading all the data and dumping the useful data back to the file works like putting the data to a newly created file. My question is whether there exist a more efficient library for me to insert/delete characters in any position of a file. Anyway, thanks for your response.
# 7  
Old 10-07-2004
Quote:
Originally posted by Driver
> If you have the memory, you might want to read the whole file into memory, manipulate it there and then dump the results back to disk.

Well, if one really wants to modify it in memory, one could also mmap() the file. Using MAP_SHARED you won't need any memory to back the file, as it is already done by the disk. memmove() to move data to make room/overwrite areas of the file and ftruncate() to grow/shrink the file. But I do not recommend this because it likely does not buy anything and may well be slower, requires more effort and decreases the degree of portability.
Yes, I agree, which is why I say "could". A lot depends on machine specs and the problem itself. The problem described is quite simple, but a mail merge application, indexing or sorting application will require due consideration to performance.

My point to the OP was quite simple and old fashioned: memory is faster than disk!

( I hope that is still true these days Smilie )

Peace Smilie

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