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+# Backup if change
+This script help you to backup a file when it is detected changed, this script will copy the file to `--target-dir` with datetime as suffix.
+
+## How it work
+
+Just re-calculate the file's hash every a few seconds, when different with last result, copy it.
+
+## Usage
+
+```
+$ ./backup-if-change.sh
+option(s) --file or --target-dir is unspecified.
+./backup-if-change.sh usage:
+  --target-dir    Directory to store the backup files
+  --file          The file to monitor
+  --hash-tool     Tools to calculate hash of file, default sha256sum
+  --internel      Seconds between checking file, default 32s
+
+$ /path/to/backup-if-change.sh --file user3.dat --target-dir backup_dir --internel
+2022-12-22T16:54:39,238228917+08:00 -- the hash now: c70f38d56b157a956249e43ad944bc990266b57ec0332d0596c30c73c3c19b01  user3.dat
+2022-12-22T16:54:39,239715425+08:00 -- backuping the file to user3.dat_2022-12-21T22:09:17+08:00
+2022-12-22T17:06:39,249323113+08:00 -- the hash now: ff2ab6b64f46c1ca2d7002c3c0f0818707ad2a920b36dba6f009728fdd12f7a4  user3.dat
+2022-12-22T17:06:39,251145398+08:00 -- backuping the file to user3.dat_2022-12-22T17:04:32+08:00
+^C
+```
+
+## License
+
+```
+MIT License
+
+Copyright (c) 2022 Leafee98
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+```
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