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I'm trying to achieve unlimited or simply very large number of lines saved beyond the top of the screen in XTerm. I do have my xterm*savelines: 10000000 resource set to a rather large number, and I indeed see the result of increasing savelines, but it's not even near the value of 10000000 in practice. Apparently, there seems to be some cap on the number of lines saved and it's not very large (my dmesg doesn't fit for instance). That was never a problem with konsole.

Is it possible to increase that number or make it unlimited in XTerm?

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xterm stores saved-lines in memory, allocates those at startup (or if the window is resized, since the width can vary). The feature was rewritten starting in 2009 with patch #244 to make it more efficient than the original (which was noticeably slow at much lower than 10 million lines).

konsole has a dialog allowing "unlimited" lines, which stores the scrollback on disk (in turn, not really "unlimited", and guaranteed to be slower than an in-memory approach).

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  • Thanks a lot for the explanation Thomas! However, at the current max buffer size xterm is super fast (I cannot notice any delay) and I am definitely willing to compromise the speed to get a larger buffer. Could you tell me why it's not possible to go beyond some max value? Aug 3, 2015 at 0:54
  • It might run out of memory, but there is no hardcoded limit on the number of saved lines. In a quick check on a machine with 1GB, 20 million lines is too much, but 15 million fits. On the other hand, if the actual limit (as used) were something like 65 thousand, that could be a bug to investigate. Aug 3, 2015 at 1:05
  • With a simple test for i in $(seq 1082); do echo $i; done I can see that my limit is 1083 lines despite the setting of xterm*savelines: 10000000. Is there a simple way to see if XTerm is aware of my setting? Aug 3, 2015 at 1:10
  • Ok, xterm -sl 1000000 does seem to work as expected. I must be doing something wrong with the XResources configuration then I guess? Aug 3, 2015 at 1:16
  • Now that is actually embarassing, I think the problem was simply xterm*savelines instead of xterm*saveLines. Thanks for your help Thomas! Aug 3, 2015 at 1:45

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