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

Answer 1

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

Answer 2

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
}

Answer 3

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.

Answer 4

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

Answer 5

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

Answer 6

{
  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