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You need to use the following key combination to scroll up and look at your data under GNU screen. First press:

CTRL-A

Next press:
[

This will activate copy mode in GNU/screen. Now, you can scroll up/down and look at your data. Use the following keys:

  * Unordered List ItemCTRL-u and CTRL-d scroll the display up/down by the specified amount of lines while preserving the cursor position. (Default: half screen-full).
  * CTRL-b and C-f scroll the display up/down a full screen.

  * To exit copy mode, press ESC
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From the man page - following movement keys can be used in copy mode:
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         h, j, k, l move the cursor line by line or column by column.
         0, ^ and $ move to the leftmost column, to the first or last non-whitespace character on the line.
         H, M and L move the cursor to the leftmost column of the top, center or bottom line of the window.
         + and - positions one line up and down.
         G moves to the specified absolute line (default: end of buffer).
         | moves to the specified absolute column.
         w, b, e move the cursor word by word.
         B, E move the cursor WORD by WORD (as in vi).
         C-u and C-d scroll the display up/down by the specified amount of lines while preserving the cursor position. (Default: half screen-full).
         C-b and C-f scroll the display up/down a full screen.
         g moves to the beginning of the buffer.
         % jumps to the specified percentage of the buffer.
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