How to save Screen scrollback to a file

When a command has already filled a Screen window, copying from the terminal or enabling logging after the fact can miss the lines that matter. The Screen hardcopy command can write the current window to a file, and the -h option expands that capture to include the scrollback buffer.

Hardcopy runs inside the selected Screen window. The default C-a h binding writes only the visible screen to hardcopy.n, while the command prompt form lets you choose a path and add -h when older lines are needed.

Use a file path you can inspect from another terminal before closing or changing the session. Screen normally overwrites an existing hardcopy file, but sessions with hardcopy_append enabled append instead, so save to a fresh path when the file is evidence for a ticket or handoff.

Steps to save Screen scrollback to a file:

Attach to the target Screen session.
```
$ screen -r work
```
Replace work with the session name shown by screen -ls.

Related: How to attach to a Screen session
Select the window whose scrollback should be saved.
```
C-a 1
```
Replace 1 with the target window number or title.

Related: How to select a window in Screen
Open the Screen command prompt from inside the selected window.
```
C-a :
```
C-a is the default command character. Use the configured prefix when the session changed it.

Related: How to use the Screen command prompt
Write the window plus its scrollback buffer to an explicit file.
```
hardcopy -h /tmp/screen-scrollback.txt
```
Use an absolute path when the saved file must be easy to find from another terminal. Without -h, hardcopy saves only the visible screen.
Verify that the saved file contains the expected older lines and the recent visible line.
```
$ cat /tmp/screen-scrollback.txt
history-line-001
history-line-002
history-line-003
##### snipped
history-line-080
visible-marker
```
If the file contains only the visible lines, confirm that the command included -h. If older output is still missing, the window's scrollback depth did not retain it.

Related: How to configure Screen scrollback
Move the file to the handoff location after verifying its contents.
```
$ cp /tmp/screen-scrollback.txt ./screen-scrollback.txt
```
Keep the original file until the copied file has been attached, archived, or reviewed.