Take text "screenshot" of current terminal contents

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?

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Answers:

Method 1

Method 2

Answers:

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Method 1

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.

Method 2

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

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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