bash script, erase previous line?

Question

In lots of Linux programs, like curl, wget, and anything with a progress meter, they have the bottom line constantly update, every certain amount of time. How do I do that in a bash script? All I can do now is just echo a new line, and that's not what I want because it builds up. I did come across something that mentioned "tput cup 0 0", but I tried it and it's kind of quirky. What's the best way?

I think this can be done with ncurses but maybe there's a better way - I'd be curious to find out too — naumcho, May 02 '11 at 19:20
After reading the answers, the gist of what I got was `'\r'` rewinds to the beginning of the line. so just echo without a newline [`-n`] and then `echo -ne '\r' will go back to the beginning of the line. — Matt, May 03 '11 at 00:09

score 45 · Accepted Answer · answered May 02 '11 at 19:43

45

{
  for pc in $(seq 1 100); do
    echo -ne "$pc%\033[0K\r"
    usleep 100000
  done
  echo
}

The "\033[0K" will delete to the end of the line - in case your progress line gets shorter at some point, although this may not be necessary for your purposes.

The "\r" will move the cursor to the beginning of the current line

The -n on echo will prevent the cursor advancing to the next line

answered May 02 '11 at 19:43

linuts

6,608
4
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awesome! great little example – naumcho May 02 '11 at 19:45

score 19 · Answer 2 · answered Jul 05 '14 at 10:55

19

You can also use tput cuu1;tput el (or printf '\e[A\e[K') to move the cursor up one line and erase the line:

for i in {1..100};do echo $i;sleep 1;tput cuu1;tput el;done

answered Jul 05 '14 at 10:55

Lri

26,768
8
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1

That `printf '\e[A\e[K'` was the only solution that actually did the trick for me! Thanks for sharing it! – João Ciocca Sep 30 '22 at 21:04

score 13 · Answer 3 · answered May 03 '11 at 08:19

13

Small variation on linuts' code sample to move the cursor not to the beginning, but the end of the current line.

{
  for pc in {1..100}; do
    #echo -ne "$pc%\033[0K\r"
    echo -ne "\r\033[0K${pc}%"
    sleep 1
  done
  echo
}

answered May 03 '11 at 08:19

tom

139
2

score 8 · Answer 4 · answered May 02 '11 at 19:20

8

printf '\r', usually. There's no reason for cursor addressing in this case.

answered May 02 '11 at 19:20

geekosaur

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aggregate1166877 · Answer 5 · 2020-02-09T00:52:24.883

To actually erase previous lines, not just the current line, you can use the following bash functions:

# Clears the entire current line regardless of terminal size.
# See the magic by running:
# { sleep 1; clear_this_line ; }&
clear_this_line(){
        printf '\r'
        cols="$(tput cols)"
        for i in $(seq "$cols"); do
                printf ' '
        done
        printf '\r'
}

# Erases the amount of lines specified.
# Usage: erase_lines [AMOUNT]
# See the magic by running:
# { sleep 1; erase_lines 2; }&
erase_lines(){
        # Default line count to 1.
        test -z "$1" && lines="1" || lines="$1"

        # This is what we use to move the cursor to previous lines.
        UP='\033[1A'

        # Exit if erase count is zero.
        [ "$lines" = 0 ] && return

        # Erase.
        if [ "$lines" = 1 ]; then
                clear_this_line
        else
                lines=$((lines-1))
                clear_this_line
                for i in $(seq "$lines"); do
                        printf "$UP"
                        clear_this_line
                done
        fi
}

Now, simply call erase_lines 5 for example to clear the last 5 lines in the terminal.

This is close(r), but ignores the possibility that there are fewer lines on the display than requested. — Thomas Dickey, Aug 12 '23 at 10:48

score 0 · Answer 6 · answered Oct 30 '20 at 19:38

0

man terminfo(5) and look at the "cap-nam" column.

clr_eol=$(tput el)
while true
do
    printf "${clr_eol}your message here\r"
    sleep 60
done

answered Oct 30 '20 at 19:38

Bruce K

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15

bash script, erase previous line?

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