How to display and refresh multiple lines in bash

Question

I am writing a installation script and would like to display the status of the script as it progresses.

example:

var1=\"pending\"
var2=\"pending\"
va         


        

Answer 1

This code should give you the idea:

while :; do
    echo "$RANDOM"
    echo "$RANDOM"
    echo "$RANDOM"
    sleep 0.2
    tput cuu1 # move cursor up by one line
    tput el # clear the line
    tput cuu1
    tput el
    tput cuu1
    tput el
done

Use man tput for more info. To see the list of capabilities use man terminfo

Answer 2

Look at this:

while true; do echo -ne "`date`\r"; done

and this:

declare arr=(
  ">...."
  ".>..."
  "..>.."
  "...>."
  "....>"
)

for i in ${arr[@]}
do
  echo -ne "${i}\r"
  sleep 0.1
done

Answer 3

This does not completely solve your problem but might help; to print the status after the execution of each command, modify PS1 like this:

PS1='$PS1 $( print_status )'

Answer 4

You can use the carriage return to change text on a single status line.

n=0
while true; do
  echo -n -e "n: $n\r"
  sleep 1
  n=$((n+1))
done

If you can put all your counters on one line

n=0
m=100
while true; do
  echo -n -e "n: $n  m: $m\r"
  sleep 1
  n=$((n+1))
  m=$((m-1))
done

This technique doesn't seem to scale to multiple lines, though it does have the benefit over tput that it works on dumb terminals (like Emacs shell).

Answer 5

I find another solution which is not mentioned in existing answers. I am developing program for openwrt, and tput is not available by default. The solution below is inspired by Missing tput and Cursor Movement.

- Position the Cursor:
  \033[<L>;<C>H
     Or
  \033[<L>;<C>f
  puts the cursor at line L and column C.
- Move the cursor up N lines:
  \033[<N>A
- Move the cursor down N lines:
  \033[<N>B
- Move the cursor forward N columns:
  \033[<N>C
- Move the cursor backward N columns:
  \033[<N>D

- Clear the screen, move to (0,0):
  \033[2J
- Erase to end of line:
  \033[K

- Save cursor position:
  \033[s
- Restore cursor position:
  \033[u

As for your question:

var1="pending"
var2="pending"
var3="pending"

print_status () {
    # add \033[K to truncate this line
    echo "Status of Item 1 is: "$var1"\033[K"
    echo "Status of Item 2 is: "$var2"\033[K"
    echo "Status of Item 3 is: "$var3"\033[K"
}

while true; do 
    print_status
    sleep 1
    printf "\033[3A"    # Move cursor up by three line
done