Access xterm's scrollback buffer as a file

Question

Is it possible to, somehow, access xterm's scrollback buffer as a (read-only) file or a character device?

The core issue (to avoid x/y "problemming"), is this: sometimes the command I've just executed creates non-deterministic output, and I'd like to use its output somehow without pre-thought of tee-ing it. Right now, the only way to do this (that I'm aware of) is to use the mouse to select the text into primary selection.

Alternative to using tee. Have you considered running script to create a log of all your commands to a file? — Stephen Quan, Apr 30 '18 at 00:16

Thomas Dickey · Accepted Answer · 2019-10-19T18:07:09.840

10

You could do this by telling xterm to print the data using the print-everything action (normally not bound to a key).

Alternatively, there's an escape sequence documented in XTerm Control Sequences:

CSI ? Pm i                                                                      
          Media Copy (MC), DEC-specific.                                        
            Ps = 1  -> Print line containing cursor.                            
            Ps = 4  -> Turn off autoprint mode.                                 
            Ps = 5  -> Turn on autoprint mode.                                  
            Ps = 1  0  -> Print composed display, ignores DECPEX.               
            Ps = 1  1  -> Print all pages.

which could be invoked as

printf '\033[?11i'

But either approach (to write to a file) would need a printerCommand configured.

edited Oct 19 '19 at 18:07

answered Apr 29 '18 at 16:29

Thomas Dickey

76,765

Is it possible to do that without restarting xterm? If it involves restarting xterm it is not really an answer as that would cause the output to be lost. – kasperd Apr 29 '18 at 17:54
This is what I was looking for. Resources can be reloaded on the fly, and I'm OK to restart xterm. I've created a named fifo and configured it into printerCommand, have bound print-everything command to a key and it works exactly as I wanted it to. – John Z. May 18 '18 at 18:18
This may have security implications because any program with the user rights or root rights can trigger printf '\033[?11i' > /dev/pts/[number] and then examine the output. – u_Ltd. Feb 18 '23 at 13:44
However, if this is to be configured permanently, just add this line to ~/.Xresources: xterm*VT100.printerCommand: cat >~/XTerm.pseudoprinter.out and make sure this is loaded by xrdb -load on startup (will probably happen automatically on your GNU/Linux system). – u_Ltd. Feb 18 '23 at 13:45

score 2 · Answer 2 · answered Apr 29 '18 at 16:44

2

You can always use something like tmux which provides capture-pane that does what you want, along with splits (vertical and horizontal) and multiplexing, session support, and a slew of other things.

Or use a different terminal emulator xfce4-terminal is also lightweight and provides an easy Save Contents

answered Apr 29 '18 at 16:44

Evan Carroll

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To me this does not sound like an answer to the question. None of those programs can magically capture output which at the moment exist only in an xterm window. – kasperd Apr 29 '18 at 17:56
@kasperd a fair interpretation. He wants something that captures without pre-thought. I use tmux without prethought. Then I don't have this problem. If you can get in the habit of using tmux, you'll never have to think about this again (or a lot of other stuff). – Evan Carroll Apr 29 '18 at 18:10

score 0 · Answer 3 · answered Feb 18 '23 at 13:21

You can Ctrl-Clickleft and select "Print-All Immediately" which generates the plain text file $HOME/XTermYYYY-MM-DD.hh.mm.ss

This is the default configuration which can be modified with printFileImmediate, printModeImmediate and printOptsImmediate.

Access xterm's scrollback buffer as a file

3 Answers3

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