All I can find using fopen() and fwrite() in C is to delete all contents and start writing again or append to the end of the file. What if I need to go to some offset in the file and overwrite a few bytes?
Is that possible with some function?
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You can open the file with the "rb+" option and then use fseek with SEEK_SET to go to a specific location. Therb+ opens it for both reading and writing as a binary file (the file must exist in order for it to succeed - it will not create a new file).
Mark Wilkins
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That will overwrite just the bytes I want and will not append? – rfgamaral Apr 12 '10 at 15:30
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The question is, will it discard the remainder of the file beyond what you've written? – Joe Koberg Apr 12 '10 at 15:31
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@Nazgulled: Yes - the SEEK_SET positions to a specific byte offset in the file. SEEK_CUR can also be used to seek to an offset from the current location. – Mark Wilkins Apr 12 '10 at 15:31
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5@Joe: No, it will leave the remaining data unchanged. – Mark Wilkins Apr 12 '10 at 15:32