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I have a large file (typically more than 1GB) with following format:
[header information, 128 bytes] [content, 1GB]
My question: Is there a simple way to trim the header information without have to read the content part and save to disk again? I mean I just need to modifying the existing file and delete the header part.
Update:
The header is at the beginning of the file
From the perspective of the file system, a file content is just a sequence of blocks. While file system normally allows some “slack” (i.e. unused space) in the last block (to accommodate a file size that is not multiple of block size), the file system is simply not constructed to allow any slack in the first block. In other words, the file content must begin at the beginning of the first block.
So you cannot trim arbitrary amount of data from the start of the file. Even trimming the amount of data equal to the block size is not exposed through any API I know of.