You can implement this by overwriting a line. Use \r to go back to the beginning of the line without writing \n to the terminal.
Write \n when you're done to advance the line.
Use echo -ne to:
- not print
\nand - to recognize escape sequences like
\r
Here's a demo:
echo -ne '##### (33%)\r'
sleep 1
echo -ne '############# (66%)\r'
sleep 1
echo -ne '####################### (100%)\r'
echo -ne '\n'
In a comment below, puk mentions this "fails" if you start with a long line and then want to write a short line: In this case, you'll need to overwrite the length of the long line (e.g., with spaces).