Update cheatsheets

tldr/linux/flock

@@ -5,18 +5,26 @@ source: https://github.com/tldr-pages/tldr.git
 ---
 # flock
 
-> Manage locks from shell scripts.
-> It can be used to ensure that only one process of a command is running.
+> Manage file locks from shell scripts.
+> It can be used to ensure that only one instance of a command is running.
 > More information: <https://manned.org/flock>.
 
-- Run a command with a file lock as soon as the lock is not required by others:
+- Run a command with a file lock as soon as the lock is available:
 
-`flock {{path/to/lock.lock}} {{[-c|--command]}} "{{command}}"`
+`flock {{path/to/lock.lock}} {{command}}`
 
-- Run a command with a file lock, and exit if the lock doesn't exist:
+- Run a command with a file lock, or exit if the lock is currently being held (with exit code 1):
 
-`flock {{path/to/lock.lock}} {{[-n|--nonblock]}} {{[-c|--command]}} "{{command}}"`
+`flock {{path/to/lock.lock}} {{[-n|--nonblock]}} {{command}}`
 
-- Run a command with a file lock, and exit with a specific error code if the lock doesn't exist:
+- Run a command with a file lock, or exit with a specific error code if the lock is currently being held:
 
-`flock {{path/to/lock.lock}} {{[-n|--nonblock]}} {{[-E|--conflict-exit-code]}} {{error_code}} {{[-c|--command]}} "{{command}}"`
+`flock {{path/to/lock.lock}} {{[-n|--nonblock]}} {{[-E|--conflict-exit-code]}} {{123}} {{command}}`
+
+- Run a command with a file lock, waiting up to 10 seconds for the lock to be available before giving up:
+
+`flock {{path/to/lock.lock}} {{[-w|--timeout]}} 10 {{command}}`
+
+- Backup a bunch of files, waiting for the previous `tar` command to finish if it's still running elsewhere and holding the same lock file (can be used in a `cron` job that runs often):
+
+`flock {{path/to/backup.lock}} {{tar -cvf path/to/backup.tar path/to/data/}}`