I am having difficulties finding how Rsync chooses the extension for the temporary file created while copying the file if I don't use the --inplace option. Example : I want to copy sourceDirectory/myFile.txt into targetDirectory/ with Rsync.While copying myFile.txt into targetDirectory/ Rsync will create a file named .myFile.txt.W4zvLi  in targetDirectory/.Then Rsync will rename .myFile.txt.W4zvLi into myFile.txt.The question is how why Rsync uses the W4zvLi extension and why it seems to change each time I execute the Rsync program?
Rsync temporary file extension
rsync;filenames
rsync uses the mktemp(3) POSIX function to generate a unique temporary file name.  You pass a template string to the mktemp function, and it will return a file name with any X characters in the template replaced by a random character.In particular, rsync passes .XXXXXX to mktemp.  If you want to try it out from the command line you can use the mktemp(1) binary like so:mktemp -u /tmp/foo.XXXXXX