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Comment: printf instead of echo -n, and avoid embedding parameter expansion inside printf's format string
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Comment: mark examples by requirements, make the POSIX one really POSIX, make them functions, and show how to call them
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| i=0 sp="/-\|" n=${#sp} printf ' ' while true; do |
# Bash, with GNU sleep spin() { local i=0 local sp='/-\|' local n=${#sp} printf ' ' sleep 0.1 while true; do |
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| done | sleep 0.1 done } |
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| 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`). |
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| sp='/-\|' printf ' ' while true; do |
# POSIX sh spin() { sp='/-\|' printf ' ' sleep 1 while true; do |
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| done | sleep 1 done } |
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| 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: | One way to use these spinners in a script is to run them as background processes, and kill them when you're done. For example, |
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| sp="/-\|" | # POSIX sh spin & spinpid=$! # long-running commands here kill "$spinpid" }}} If you already have a loop which does a lot of work, you can write a function that "advances" the spinner one step at a time, and call it at the beginning of each iteration: {{{ # Bash, with GNU sleep sp='/-\|' |
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| printf "\b${sp:sc++:1}" ((sc==${#sp})) && sc=0 |
printf "\b${sp:sc++:1}" ((sc==${#sp})) && sc=0 sleep 0.1 |
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| printf "\r%s\n" "$@" | printf '\r%s\n' "$*" sleep 0.1 |
Can I do a spinner in Bash?
Sure!
# Bash, with GNU sleep
spin() {
local i=0
local sp='/-\|'
local 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 ${#sp} is the length of the sp string).
The \b string is replaced by a 'backspace' character. Alternatively, you could play with \r to go back to the beginning of the line.
To slow it down, the sleep command is included inside the loop (after the printf).
A POSIX equivalent would be:
# POSIX sh
spin() {
sp='/-\|'
printf ' '
sleep 1
while true; do
printf '\b%.1s' "$sp"
sp=${sp#?}${sp%???}
sleep 1
done
}One way to use these spinners in a script is to run them as background processes, and kill them when you're done. For example,
# POSIX sh spin & spinpid=$! # long-running commands here kill "$spinpid"
If you already have a loop which does a lot of work, you can write a function that "advances" the spinner one step at a time, and call it at the beginning of each iteration:
# Bash, with GNU sleep
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
endspinA similar technique can be used to build progress bars.