Diff for "BashFAQ/034"

Differences between revisions 3 and 13 (spanning 10 versions)

Can I do a spinner in Bash?

Sure!

i=0
sp='/-\|'
n=${#sp}
printf ' '
sleep 0.1
while true; do
    printf '\b%s' "${sp:i++%n:1}"
    sleep 0.1
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 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.

To slow it down, the sleep command is included inside the loop (after the printf).

A POSIX equivalent would be:

sp='/-\|'
printf ' '
sleep 0.1
while true; do
    printf '\b%.1s' "$sp"
    sp=${sp#?}${sp%???}
    sleep 0.1
done

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
    sleep 0.1
}
endspin() {
    printf '\r%s\n' "$@"
    sleep 0.1
}
until work_done; do
   spin
   some_work ...
done
endspin

A similar technique can be used to build progress bars.

CategoryShell

-  ⇤ ← Revision 3 as of 2008-05-16 19:18:22 → 
  Size: 1045
  Editor: GreyCat
  Comment: clean up
+   ← Revision 13 as of 2017-03-31 05:46:23 → ⇥
  Size: 1318
  Editor: r180-216-10-159
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 1:
-[[Anchor(faq34)]]
+<<Anchor(faq34)>>
 Line 3:
-Sure.
+Sure!
-Line 5:
+Line 6:
-i=1
sp="/-\|"
echo -n ' '
while true
do
    printf "\b${sp:i++%${#sp}:1}"
+i=0
sp='/-\|'
n=${#sp}
printf ' '
sleep 0.1
while true; do
    printf '\b%s' "${sp:i++%n:1}"
    sleep 0.1
-Line 14:
+Line 17:
-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 `${#sp}` is the [:BashFAQ/007:length] of the `sp` string).
+Each time the loop iterates, it displays the next character in the `sp` string, wrapping around as it reaches the end.  (`i` is the position of the current character to display and `${#sp}` is the [[BashFAQ/007|length]] of the `sp` string).
-Line 18:
+Line 21:
-If you want it to slow down, put a {{{sleep}}} command inside the loop (after the printf).
+To slow it down, the `sleep` command is included inside the loop (after the `printf`).

A POSIX equivalent would be:

{{{
sp='/-\|'
printf ' '
sleep 0.1
while true; do
    printf '\b%.1s' "$sp"
    sp=${sp#?}${sp%???}
    sleep 0.1
done
}}}
-Line 21:
+Line 37:
-Line 22:
+Line 39:
-sp="/-\|"
+sp='/-\|'
-Line 25:
+Line 42:
-   printf "\b${sp:sc++:1}"
   ((sc==${#sp})) && sc=0
+    printf "\b${sp:sc++:1}"
    ((sc==${#sp})) && sc=0
    sleep 0.1
-Line 29:
+Line 47:
-   printf "\r%s\n" "$@"
+    printf '\r%s\n' "$@"
    sleep 0.1
-Line 31:
+Line 50:
-Line 39:
+Line 57:
-A similar technique can be used to build progress bars.
+A similar technique can be used to build [[BashFAQ/044|progress bars]].

----
CategoryShell