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Size: 1692
Comment: mark examples by requirements, make the POSIX one really POSIX, make them functions, and show how to call them
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← Revision 16 as of 2023-10-26 18:03:57 ⇥
Size: 1593
Comment: check exit status of sleep, and avoid repetition of sleep command
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| Deletions are marked like this. | Additions are marked like this. |
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| sleep 0.1 while true; do |
while sleep 0.1; do |
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| sleep 0.1 | |
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| sleep 1 while true; do |
while sleep 1; do |
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| sleep 1 | |
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| # Bash, with GNU sleep | # Bash |
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| sn=${#sp} | |
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| printf "\b${sp:sc++:1}" ((sc==${#sp})) && sc=0 sleep 0.1 |
printf '\b%s' "${sp:sc++%sn:1}" |
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| sleep 0.1 |
Can I do a spinner in Bash?
Sure!
# Bash, with GNU sleep
spin() {
local i=0
local sp='/-\|'
local n=${#sp}
printf ' '
while sleep 0.1; do
printf '\b%s' "${sp:i++%n: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 ${#sp} is the length of the sp string).
The \b string is replaced by a 'backspace' character. Alternatively, you could play with \r to go back to the beginning of the line.
To slow it down, the sleep command is included inside the loop (after the printf).
A POSIX equivalent would be:
# POSIX sh
spin() {
sp='/-\|'
printf ' '
while sleep 1; do
printf '\b%.1s' "$sp"
sp=${sp#?}${sp%???}
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
sp='/-\|'
sc=0
sn=${#sp}
spin() {
printf '\b%s' "${sp:sc++%sn:1}"
}
endspin() {
printf '\r%s\n' "$*"
}
until work_done; do
spin
some_work ...
done
endspinA similar technique can be used to build progress bars.