9

I would like to, every 30 seconds or so, copy all text of a certain terminal or terminal emulator to a file, and display it in conky. I'm not talking about simple redirection (command > file), which doesn't work for ncurses programs or games such as NetHack.

How could I go about doing this?

IBPX
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    if it's a console terminal, you can get the contents from /dev/vcs* – Jasen Nov 09 '15 at 08:57
  • That'll work! Is it possible to open more than the default 6 (or whatever your distro uses)? – IBPX Nov 09 '15 at 17:53
  • You want text, so the accepted screen answer is indeed right. But for others who land here looking for a graphic screenshot of a Linux console running without X or any GUI, there is fbgrab as suggested in https://askubuntu.com/a/558588/8822 – mivk Jan 09 '18 at 12:25

2 Answers2

7

There is no portable way to ask a terminal emulator to do screen dumps. You can work around this by running your application in GNU screen or tmux and using them to carry out the screen-dumps.

GNU screen can do this:

Likewise, there is a plugin for tmux to do screen captures.

Community
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Thomas Dickey
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0

capture the *visible* output of a process (text screenshot)

this will render special characters like carriage return (\r) and other terminal control codes as they would be visible to a human

for example, a live progress bar should produce

[================================>] 100%

and not

[==>                               ]  9%
[========>                         ] 28%
[==============>                   ] 47%
[=====================>            ] 65%
[===========================>      ] 84%
[================================>] 100%

#! /usr/bin/env bash

text screenshot


capture the visible output of a process


https://unix.stackexchange.com/a/697804/295986


captureCommand="$(cat <<'EOF'


example: progress bar


https://stackoverflow.com/a/23630781/10440128


for ((i=0; i<100; i++)); do
    sleep 0.1
    printf .
  done | pv -p -c -s 100 -w 40 > /dev/null
EOF
)"


note: to stop the captureCommand after some time


you can wrap it in timeout -k 60 60


to stop after 60 seconds


or use for waiterStep in $(seq 0 60)


in the waiter loop


create a new screen session. dont attach


screenName=$(mktemp -u screen-session-XXXXXXXX)
screen -S "$screenName" -d -m


create lockfile


screenLock=$(mktemp /tmp/screen-lock-XXXXXXXX)


remove lockfile after captureCommand


screenCommand="$captureCommand; rm $screenLock;"


echo "start captureCommand"


send text to detached screen session


^M = enter


screen -S "$screenName" -X stuff "$screenCommand^M"
hardcopyFile=$(mktemp /tmp/hardcopy-XXXXXXXX)


enableWatcher=true
if $enableWatcher; then
  echo "start watcher"
  (
    # watcher: show live output while waiting
    while true
    #for watcherStep in $(seq 0 100) # debug
    do
      sleep 2
      # take screenshot. -h = include history
      screen -S "$screenName" -X hardcopy -h "$hardcopyFile"
      cat "$hardcopyFile"
    done
  ) &
  watcherPid=$!
fi


echo "wait for captureCommand ..."
while true
#for waiterStep in $(seq 0 60) # debug
do
  sleep 1
  [ -e "$screenLock" ] || break
done
echo "done captureCommand"


if $enableWatcher; then
  kill $watcherPid
fi


take a last screenshot


screen -S "$screenName" -X hardcopy -h "$hardcopyFile"
echo "done hardcopy $hardcopyFile"


kill the detached screen session


screen -S "$screenName" -X quit
milahu
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