44 lines
1.4 KiB
Bash
44 lines
1.4 KiB
Bash
# create a lock using `flock(2)`. A name is required as first argument.
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# the lock will be automatically unlocked when the shell process quits.
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# Noted due to the fixed FD, a shell process can only create one lock.
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lock() {
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local name="$1"
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local lock_dir="$HOMEBREW_LIBRARY/Locks"
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local lock_file="$lock_dir/$name"
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[[ -d "$lock_dir" ]] || mkdir -p "$lock_dir"
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# 200 is the file descriptor used in the lock.
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# This FD should be used exclusively for lock purpose.
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# Any value except 0(stdin), 1(stdout) and 2(stderr) can do the job.
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# Noted, FD is unique per process but it will be shared to subprocess.
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# It is recommended to choose a large number to avoid conflicting with
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# other FD opened by the script.
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#
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# close FD first, this is required if parent process holds a different lock.
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exec 200>&-
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# open the lock file to FD, so the shell process can hold the lock.
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exec 200>"$lock_file"
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if ! _create_lock 200
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then
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odie <<EOS
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Another active Homebrew process is already in progress.
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Please wait for it to finish or terminate it to continue.
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EOS
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fi
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}
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_create_lock() {
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local lock_fd="$1"
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local ruby="/usr/bin/ruby"
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[[ -x "$ruby" ]] || ruby="$(which ruby 2>/dev/null)"
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if [[ -n "$ruby" ]]
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then
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"$ruby" -e "File.new($lock_fd).flock(File::LOCK_EX | File::LOCK_NB) || exit(1)"
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elif [[ -n "$(which flock)" ]]
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then
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flock -n "$lock_fd"
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else
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onoe "Cannot create lock, please avoid running brew in parallel."
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fi
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}
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