A Linux administrator needs to back up files from a user's home directory to a remote server. The administrator copied the files last week but must ensure any files created or modified since then…

scp always transfers every specified file unconditionally with no ability to skip files that already exist unchanged on the destination, so it cannot perform incremental backups.

rsync compares source and destination files using checksums and timestamps, then transfers only the differences - making it ideal for incremental backups after an initial full copy. The -r flag enables recursive directory traversal, and rsync natively supports remote targets over SSH using the user@host:/path syntax.

cp operates only on locally mounted filesystems and cannot transfer files to a remote server over the network.

sftp -b executes a batch file of SFTP commands, not a file glob path, so this syntax is invalid and sftp has no built-in incremental or differential transfer capability.