mv

What it does

mv moves files or directories to a new location, or renames them if the destination is within the same directory. Unlike cp, it doesn't leave a duplicate behind — the source path stops existing once the move completes. Renaming is really just a special case of moving: giving a new path in the same directory.

Beginner examples

• mv oldname.txt newname.txt — rename a file
• mv file.txt /var/backups/ — move a file into another directory, keeping its name
• mv -i draft.txt final.txt — prompt for confirmation before overwriting final.txt if it exists
• mv old_project/ new_project/ — rename or relocate an entire directory in one command

mv draft.txt final.txt

Advanced examples

• Move several files into a directory at once: mv *.log /var/backups/ moves every matching file, keeping each one's original name inside the destination directory.
• Avoid clobbering existing files during a bulk move: mv -n *.conf /etc/app/conf.d/ skips any file that already exists at the destination instead of overwriting it.
• Move only newer files, useful for simple one-way syncs: mv -u *.csv /data/processed/.
• Understand the cross-filesystem cost: moving a large file between different mounted filesystems (mv /mnt/diskA/bigfile /mnt/diskB/) is a full copy-then-delete internally, unlike a same-filesystem move, which is a near-instant rename.

mv -vn *.log /var/backups/

Common mistakes

• Assuming a move across filesystems (e.g. between two different mounted drives) is instant like a same-filesystem rename — it's actually a full copy followed by deleting the original, so it takes time and requires enough free space at the destination.
• Not noticing that if the destination is an existing directory, the source is moved into it rather than replacing it — mv report.txt existing_dir results in existing_dir/report.txt, not existing_dir being replaced by report.txt.
• Overwriting an important file by mistake because mv doesn't prompt by default — always consider -i or -n for anything not fully scripted and verified.
• Forgetting a trailing slash mismatch when moving multiple sources into a destination that doesn't yet exist, causing mv to treat the last argument as a rename target instead of a directory to move into.

Tips

• Use -i interactively whenever overwriting the wrong file would be costly, and -n in scripts where you want a guaranteed no-clobber guarantee without prompts.
• Remember that a same-filesystem mv is nearly instantaneous regardless of file size, since it's just a metadata change — useful to know when moving very large files.
• When moving a directory, double check whether the destination already exists: if it does, your source becomes a subdirectory of it rather than replacing it.

Best practices

• Use -n in automated or scripted moves to avoid silently overwriting files that may already exist at the destination, especially in shared directories.
• Prefer mv over cp + rm when relocating files — it's atomic on the same filesystem (no window where both copies exist, or where a crash mid-copy leaves partial data) and avoids the extra step of manually deleting the source.
• Be explicit about trailing slashes and destination existence when scripting moves of multiple files, to avoid ambiguity about whether the last argument is a directory or a rename target.

Real-world use cases

• Renaming a draft file to its final name once work on it is complete: mv draft.md README.md.
• Archiving log files into a dated backup directory as part of a log-rotation script.
• Reorganizing a project's directory structure by moving files and folders into new locations without duplicating data.

Common interview questions

• What's the difference between mv and cp? mv relocates or renames a file, removing it from its original path; cp creates a separate duplicate and leaves the original untouched.
• Why is moving a file within the same filesystem much faster than moving it across filesystems? A same-filesystem move is just a directory-entry rename — an essentially instant metadata operation. A cross-filesystem move requires mv to copy the actual data to the new filesystem and then delete the original, which scales with file size.
• What happens when you mv a file into a path that is an existing directory versus one that isn't? If the destination is an existing directory, the file is moved into it under its original name; if the destination doesn't exist as a directory, mv treats it as the new full name/path for the file, effectively renaming it.