CODEWITHSUNDEEP
bashansi-escapeterminfo
Matt
Matt

Reputation: 2896

bash script, erase previous line?

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?

Upvotes: 29

Views: 29155

Answers (6)

Bruce K
Bruce K

Reputation: 769

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

Upvotes: 1

aggregate1166877
aggregate1166877

Reputation: 3150

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.

Upvotes: 8

Lri
Lri

Reputation: 27613

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

Upvotes: 22

tom
tom

Reputation: 159

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
}

Upvotes: 15

linuts
linuts

Reputation: 6748

{
  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

Upvotes: 46

geekosaur
geekosaur

Reputation: 61379

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

Upvotes: 9

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