Diff for "BashFAQ/034"

Differences between revisions 2 and 3

Can I do a spinner in Bash?

Sure.

i=1
sp="/-\|"
echo -n ' '
while true
do
    printf "\b${sp:i++%${#sp}:1}"
done

Each time the loop iterates, it displays the next character in the sp string, wrapping around as it reaches the end. (i is the position of the current character to display and ${#sp} is the [:BashFAQ/007:length] of the sp string).

The \b string is replaced by a 'backspace' character. Alternatively, you could play with \r to go back to the beginning of the line.

If you want it to slow down, put a sleep command inside the loop (after the printf).

If you already have a loop which does a lot of work, you can call the following function at the beginning of each iteration to update the spinner:

sp="/-\|"
sc=0
spin() {
   printf "\b${sp:sc++:1}"
   ((sc==${#sp})) && sc=0
}
endspin() {
   printf "\r%s\n" "$@"
}

until work_done; do
   spin
   some_work ...
done
endspin

A similar technique can be used to build progress bars.

-  ⇤ ← Revision 2 as of 2008-05-09 11:14:31 → 
  Size: 1136
  Editor: Lhunath
  Comment: echo -ne -> printf; explain the code a little.  add an example loop for the function that is to be called within a loop.
+   ← Revision 3 as of 2008-05-16 19:18:22 → ⇥
  Size: 1045
  Editor: GreyCat
  Comment: clean up
-Deletions are marked like this.
+Additions are marked like this.
 Line 5:
-    i=1
    sp="/-\|"
    echo -n ' '
    while true
    do
        printf "\b${sp:i++%${#sp}:1}"
    done
+i=1
sp="/-\|"
echo -n ' '
while true
do
    printf "\b${sp:i++%${#sp}:1}"
done
 Line 14:
-The theory here is that each time the loop iterates, it displays the next character in the `sp` string, wrapping around as it reaches the end (where `i` is the position of the current character to display and `${#sp}` is the length of the `sp` string).
+Each time the loop iterates, it displays the next character in the `sp` string, wrapping around as it reaches the end.  (`i` is the position of the current character to display and `${#sp}` is the [:BashFAQ/007:length] of the `sp` string).
 Line 20:
-If you already have a loop which does a lot of work, you can call the following function at the beginning of each iteration in that loop to update the spinner every time an iteration of your loop begins:
+If you already have a loop which does a lot of work, you can call the following function at the beginning of each iteration to update the spinner:
 Line 26:
-   ((sc==4)) && sc=0
+   ((sc==${#sp})) && sc=0
 Line 34:
-   some_work
+   some_work ...