How do I prepend data to a file, take out/delete data from the middle of the file or insert data into the middle of the file?
Files in UNIX can be thought of as big sequences of octets, and as such it is possible to overwrite existing bytes with new ones, to append to the end of the file, or to truncate a file from a position to the end (to create a file which is shorter than the existing one.). However, it’s not easily possible to prepend data to the beginning of the file, to take out/delete data from the middle of the file or to insert it into the middle of the file while only using a single file handle to the file. The best way to achieve what you want with such operations is to write a new file with the modified content, then close both files and move the new file on top of the existing files using rename.
