To delete all content from current position to the end of file on bash, you can take the following steps:

• Open file in vi or vim
  

  $> vi fiele
  $> # or
  $> vim file

• Switch to visual block mode

  Ctrl+v

• Press G (Shift+g)
• Mark text to delete with arrow keys top and down or just press END to mark everything to the end of file
• Press D (Shift+d) to delete selected lines