How to print out to the same line, overriding previous line?

Question

Sometimes I see some commands in the terminal that print results to stdout but in the same line. For example wget prints an arrow like below:

0[=>        ]100%
0[  =>      ]100%
0[    =>    ]100%
0[      =>  ]100%
0[        =>]100%

but it is printed out to the same line so it looks like the arrow is moving. How can I achieve the same thing in my programs using bash or sh? Do I need to use other tools?

UPDATE:

I know I mentioned wget, which comes by default in linux, GNU based unices ... Is there a general approach that works on BSDs too? (like OSX) -> OK, If I use bash instead of sh then it works :)

http://stackoverflow.com/questions/12628327/how-to-show-and-update-echo-on-same-line — devnull, Aug 02 '13 at 13:16
http://stackoverflow.com/questions/3372673/continue-output-on-same-line — devnull, Aug 02 '13 at 13:17

choroba · Accepted Answer · 2013-08-02T13:17:18.397

17

Use the special character \r. It returns to the beginning of the line without going to the next one.

for i in {1..10} ; do
    echo -n '['
    for ((j=0; j<i; j++)) ; do echo -n ' '; done
    echo -n '=>'
    for ((j=i; j<10; j++)) ; do echo -n ' '; done
    echo -n "] $i"0% $'\r'
    sleep 1
done

edited Aug 02 '13 at 13:17

answered Aug 02 '13 at 12:49

choroba

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Great answer, @choroba. This makes it complete: `for i in {1..10} ; do echo -n "0[ "; for ((j=0; j' ; for ((j=i;j<=10;j++)) ; do echo -n ' '; done; echo -n $'] 100% \r'; sleep 1; done` – fedorqui Aug 02 '13 at 13:03

score 12 · Answer 2 · answered Aug 02 '13 at 12:49

12

You can use \r for this purpose:

For example this will keep updating the current time in the same line:

while true; do echo -ne "$(date)\r"; done

answered Aug 02 '13 at 12:49

fedorqui

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1

also note that it won't work with POSIX `echo` command, but it works nice in `bash` – rook Aug 02 '13 at 13:10
1

True, for portability reasons `printf` should be preferred over `echo` with option arguments. – Adrian Frühwirth Aug 02 '13 at 13:13

user1146332 · Answer 3 · 2013-08-02T13:57:14.500

You can also use ANSI/VT100 terminal escape sequences to achieve this.

Here is a short example. Of course you can combine the printf statements to one.

#!/bin/bash

MAX=60
ARR=( $(eval echo {1..${MAX}}) )

for i in ${ARR[*]} ; do 
    # delete from the current position to the start of the line
    printf "\e[2K"
    # print '[' and place '=>' at the $i'th column
    printf "[\e[%uC=>" ${i}
    # place trailing ']' at the ($MAX+1-$i)'th column
    printf "\e[%uC]" $((${MAX}+1-${i}))
    # print trailing '100%' and move the cursor one row up
    printf " 100%% \e[1A\n"

    sleep 0.1
done

printf "\n"

With escape sequences you have the most control over your terminal screen.

You can find an overview of possible sequences at [1].

[1] http://ascii-table.com/ansi-escape-sequences-vt-100.php

All answers here are good, but I like this one since printf is portable. — dotokija, Aug 07 '23 at 13:56

How to print out to the same line, overriding previous line?

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