История изменений

Явно про такое написано в мане на lseek() не fseek()

lseek() allows the file offset to be set beyond the end of the file (but this does not change the size of the file). If data is later written at this point, subsequent reads of the data in the gap (a «hole») return null bytes ('\0') until data is actually written into the gap.

Явно про такое написано в мане на lseek()

lseek() allows the file offset to be set beyond the end of the file (but this does not change the size of the file). If data is later written at this point, subsequent reads of the data in the gap (a «hole») return null bytes ('\0') until data is actually written into the gap.