Add a non-busy path to safe_sleep for modern versions of bash #3870
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Rudxain
reviewed
Dec 10, 2025
| read -rt "$1" <> <(:) || : | ||
| fi | ||
| # Fallback to busy wait. | ||
| while [[ $SECONDS -lt $1 ]]; do |
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-lt is vulnerable to code-injection (SC)
Previously mentioned here
latekvo
suggested changes
Dec 11, 2025
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| # Bash 4.0 and above supports read. | ||
| if [[ -n "$BASH_VERSINFO" && "${BASH_VERSINFO[0]}" -ge 4 ]]; then | ||
| echo foo |
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Suggested change
| echo foo |
Remove debug logs
| fi | ||
| # Fallback to busy wait. | ||
| while [[ $SECONDS -lt $1 ]]; do | ||
| echo bar |
Author
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Changes incorporated here: #4146 |
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The current implementation of
safe_sleep.shis a busy wait.This seems to exist because
sleepis not a shell builtin, and it can't be assumed all environments have the sleep binary.Bash 4 and above support the builtin
readcommand, which can be used as a sleep with the timeout feature. This pattern is described here:https://github.com/dylanaraps/pure-bash-bible?tab=readme-ov-file#use-read-as-an-alternative-to-the-sleep-command
Despite Bash 4 shipping 16 years ago, bash 3.x is still the default shipped on MacOS due to 4+ being licensed as GPL3, so the busy wait was retained as a fallback.
Also the condition in the busy wait was switched from
!=to-lt, which is a safer comparison and avoids possibility of an infinite loop.Fixes #2380
#3143 has another similar approach, which relies on conditionally checking for sleep or ping binaries to provide a sleep functionality.