Integrating Rsync into a Unix pipeline can be a useful skill, whether for synchronizing directories or regularly backing up information. Rsync (remote synchronization) is a widely used tool for copying and syncing files both locally and remotely in Unix-based systems.
In a simple scenario, let’s say you want to synchronize the content of two directories. You can easily achieve this with Rsync by running `rsync -r /source_directory /destination_directory`. The ‘-r’ option is for recursively copying files in all subdirectories (Fischer, 2020).
However, to include Rsync into a Unix pipeline, you need to understand that Unix pipes work with std in and std out, while Rsync works with file system paths. Rsync doesn’t read from std in or write to std out in the same manner as other Unix commands like cat, sort, or grep that are typically used in pipelines.
That said, there is a workaround to integrate Rsync into a Unix pipeline using a named pipe (FIFO). A named pipe can be used as an intermediary between commands that do not normally communicate directly. Here’s an example:
```
mkfifo /tmp/namedPipe
command1 > /tmp/namedPipe &
rsync -av /tmp/namedPipe remote:/destination_directory
rm /tmp/namedPipe
```
In the above example, ‘command1’ is the command generating output, and ‘remote:/destination\_directory’ is the remote location where files are to be synced. Rsync reads from the named pipe and copies it to the destination.
As a use case, combining ‘find’ with ‘rsync’ through a pipeline can selectively sync files. For example, to sync only the “.txt” files modified in the last two days, you might use:
```
find /source_directory -name “*.txt” -mtime -2 > /tmp/fileList.txt
rsync —files-from=/tmp/fileList.txt / remote:/destination_directory
```
Although it appears that ‘find’ and ‘rsync’ are piped together, it’s important to notice that ‘rsync’ reads from a list generated by ‘find’, stored in a temporary file (fileList.txt).
Using Rsync in Unix pipelines might not always be straightforward but can be achieved in certain ways. It’s crucial to note that standard Unix pipes might not be compatible with Rsync due to its design. Thus, named pipes or temporary files are typically found in such instances (Panwar, 2021).
References:
1. Fischer, M. (2020). The Geek Stuff. Rsync: Preserve / Copy Hard Links (Local / Remote).
2. Panwar, S. (2021). Linux Handbook. The Right Way to Sync Files and Directories to a Remote Server Using Rsync.
