rename Command in Mac Terminal: 2 Versions, 1 Overwrites

Type rename in Terminal on macOS 26.4.1 and you get zsh: command not found: rename with exit code 127. Bash and /bin/sh say the same. Then man rename opens a page anyway, and it's the wrong one. The header reads RENAME(2) System Calls Manual, the C function a program calls to rename a file. Apple ships the system call but not the command.

Homebrew fixes the missing command in two ways, and the two don't agree. I installed both on the Mac mini that runs this business and ran them through the same fixture tests. One of them silently overwrote a file. The other reported success after a rename that failed. This post has the results, two ways to batch rename with what's already on a Mac, and a reproduction of the Ask Different question where a whole folder "disappeared."

Two rename commands, two syntaxes

Search for "rename command mac terminal" and you'll find two kinds of example. Ubuntu tutorials write rename 's/\.jpeg$/.jpg/' *.jpeg, a Perl expression. Fedora and Arch tutorials write rename .jpeg .jpg *.jpeg, plain "from, to, files." Both are called rename, and Homebrew has one of each:

• brew install rename installs version 1.601 of Aristotle Pagaltzis's Perl script. It runs on the Perl 5.34.1 that macOS still ships and goes into /opt/homebrew/bin, so it's on your PATH right away.
• brew install util-linux installs version 2.42.4 of the Linux rename that Fedora and Arch use. The util-linux formula is keg-only on macOS, so its rename lands at /opt/homebrew/opt/util-linux/bin/rename and stays off your PATH until you add it.

The Homebrew formulas list each other as conflicts only inside on_linux blocks, so on a Mac you can have both. I did, and fed each one the other's syntax:

$ rename .jpeg .jpg *.jpeg                          # brew rename (Perl)
syntax error at (eval 2) line 1, near "; ."
rc=255

$ /opt/homebrew/opt/util-linux/bin/rename 's/\.jpeg$/.jpg/' *.jpeg
rc=4                                               # no message, nothing renamed

The Perl version at least complains. util-linux treats s/\.jpeg$/.jpg/ as a literal string to look for, finds it in no filename, and exits 4 without printing anything. If a tutorial "does nothing" on your Mac, check which rename it was written for.

The util-linux one overwrites without asking

This one cost a file. I put A in a.jpeg and B in b.jpeg, then asked util-linux to rename b.jpeg to a.jpeg:

$ rename -v b a b.jpeg
`b.jpeg' -> `a.jpeg'
rc=0
$ cat a.jpeg
B

The original a.jpeg is gone. There's no prompt, no warning and exit code 0. With -o (--no-overwrite) the same command prints Skipping existing file: `a.jpeg' and exits 4, leaving both files alone. The util-linux man page lists -o and -i as options, which means overwriting is the default. If you add util-linux to your PATH, put -o in every batch command, or alias it.

The Perl version skipped the same collision with 'b.jpeg' not renamed: 'x.jpeg' already exists. It still exited 0, though.

The Perl one exits 0 when it fails

The Homebrew Perl rename returned 0 in every case I tried except a syntax error and an unknown flag. That included a skipped collision, a pattern that matched nothing, and a real failure:

$ rename 's/a/z/' data/a.jpeg
Can't rename 'data/a.jpeg' to 'dzta/a.jpeg': No such file or directory
rc=0

Two things went wrong there. The Perl expression runs on the whole path you pass, so the first a it found was in the folder name data, not in the file name. The rename then failed, and the exit code said it worked. A script that checks $? after this will carry on. util-linux only edits the last part of the path, so the same test renamed data/a.jpeg to data/z.jpeg.

How a whole folder "disappeared"

That path behavior explains an Ask Different question titled "Whole folder disappeared after running a rename command." The poster used Homebrew's rename to clean filenames before uploading to OneDrive:

find . -exec rename -s '/' '_' {} +

A file name can't contain /, so the substitution never touches a name. It hits the first / in each path that find prints, the one after the leading dot. I rebuilt it in a scratch folder with a Reports folder, two files inside it and top.txt:

$ find . -exec rename -s / _ {} +
'./Reports/a?b.docx' not renamed: '._Reports/a?b.docx' already exists
'./Reports/Q1:Q2.xlsx' not renamed: '._Reports/Q1:Q2.xlsx' already exists
rc=0
$ ls
$ ls -a
.  ..  ._Reports  ._top.txt

./Reports became ._Reports and ./top.txt became ._top.txt. Both now start with a dot, so ls and Finder hide them. Nothing was deleted, and ls -a shows them. The ._ prefix is also how macOS names AppleDouble metadata files, which cleanup tools are often set to delete, so don't let this sit.

The one answer on the question explains the hidden names correctly. It also predicts that nested files get flattened into the top folder as ._dir_foo.txt, and suggests a partial undo that turns underscores back into slashes. My rebuild didn't flatten anything. -s replaces only the first match, and once ./Reports had been renamed, the paths for its two files pointed into a folder that no longer had that name, so they were skipped and stayed inside ._Reports. That makes the undo simpler. Running rename -s '._' '' ._* in the same folder brought back Reports and top.txt with both files inside.

Case-only renames on a case-insensitive Mac

The default APFS volume on a Mac ignores case, so a.jpeg and A.jpeg are the same file. The tools disagree on what that means:

Command	a.jpeg → A.jpeg	Exit code
mv a.jpeg A.jpeg	renamed	0
mv -n a.jpeg A.jpeg	not renamed, no message	0
util-linux rename a A a.jpeg	renamed	0
Perl rename 's/^a/A/' a.jpeg	"'A.jpeg' already exists"	0
Perl rename -f 's/^a/A/' a.jpeg	renamed	0
Perl rename --upper-case a.jpeg	"'A.JPEG' already exists"	0

The Perl script checks whether the new name exists before renaming. On a case-insensitive disk it always does, because it's the same file. So its own --upper-case and --lower-case transforms do nothing without -f. Apple's mv -n fails the same way, but quietly. That's why the accepted answer on "How do I rename all files to lowercase?" (83,877 views) goes through a temporary name, mv "$f" "$f.tmp", then mv "$f.tmp" to the lowercase name.

Batch rename with what's already on a Mac

You don't need Homebrew for most batch renames. zsh, the default shell, includes zmv. It's documented in the zsh User Contributions manual, and it caught both the collision and the empty match that the other tools missed:

$ autoload -U zmv
$ zmv -n '(*).jpeg' '$1.jpg'          # dry run
mv -- a.jpeg a.jpg
mv -- b.jpeg b.jpg
mv -- 'c d.jpeg' 'c d.jpg'
$ zmv '([ab]).jpeg' 'x.jpeg'
zmv: error(s) in substitution:
b.jpeg and a.jpeg both map to x.jpeg
rc=1
$ zmv '(*).png' '$1.webp'
zmv:239: no matches found: (*).png
rc=1

It quotes names with spaces, refuses to merge two files into one, and returns 1 when nothing happened. Put autoload -U zmv in ~/.zshrc to keep it.

In bash, or anywhere you want plain POSIX tools, a loop works if you quote everything:

for f in *.jpeg; do mv -n -- "$f" "${f%.jpeg}.jpg"; done

The common shortcut for f in $(ls *.jpeg) broke on my fixture. It split c d.jpeg into c and d.jpeg and printed mv: rename c to c.jpg: No such file or directory. The top answer on "How to Batch Rename Files in a macOS Terminal?" (173,322 views, 282 points) uses the safe glob form and puts echo before mv for a dry run. For renames that span folders, pair find on Mac with -execdir. Each rename then gets ./Q1:Q2.xlsx instead of the full path, so the expression can't reach a folder name.

What 457 questions ask about renaming on a Mac

I pulled every question with "rename" in the title from Ask Different, and the macOS-tagged ones from Stack Overflow, Super User and Unix & Linux. That's 457 questions with 2,476,354 views as of 2026-10-15. I sorted the titles by keyword:

• 141 are about renaming many files at once (batch, multiple, bulk, numbering), with 671,738 views.
• 102 aren't about files at all. They cover volumes, partitions, the computer name and iPad icons, with 708,395 views.
• 5 are about case-only renames, but they have 122,859 views between them.
• 4 ask why rename is missing or how to install it, with 35,943 views.

The accepted answer to "Why is rename command missing from macOS?" explains that man rename shows the BSD system call, then recommends Homebrew's Perl rename without mentioning the exit codes or the case problem. The second-highest answer on the 173,322-view batch question also says brew install rename and then rename -nvs searchword replaceword *. That syntax works with the Perl version. It does not work with util-linux.

rename isn't the only gap. Linux scripts also expect timeout and other GNU tools that macOS doesn't ship, and in-place edits trip on sed's "invalid command code" on Mac.

FAQ

Is there a rename command on Mac?

Not by default. On macOS 26.4.1, typing rename in zsh or bash returns "command not found" with exit code 127, and man rename shows the rename(2) system call, not a command. You can install one with Homebrew (brew install rename for the Perl version, or util-linux for the Linux version), or use zsh's built-in zmv after running autoload -U zmv.

Which rename should I install with Homebrew?

Install brew install rename if you're following Ubuntu-style examples like rename 's/old/new/' *. It's on your PATH right away and won't overwrite existing files. util-linux's rename uses rename old new files, is keg-only so it isn't on your PATH, and overwrites existing files unless you pass -o. Note that the Perl version exits 0 even when a rename fails, so check its messages, not just the exit code.

How do I batch rename files in Mac Terminal without installing anything?

Use zmv, which comes with zsh, the default macOS shell. Run autoload -U zmv, preview with zmv -n '(*).jpeg' '$1.jpg', then run it without -n. zmv handles spaces, refuses when two files would end up with the same name, and exits 1 when nothing matches. In bash, use a quoted loop: for f in *.jpeg; do mv -n -- "$f" "${f%.jpeg}.jpg"; done.

How this was checked: I ran every command above on 2026-10-15 on a Mac mini M4 with macOS 26.4.1 (build 25E253), zsh 5.9 and Apple's Perl 5.34.1. Homebrew rename 1.601 and util-linux 2.42.4 were installed for the tests and removed afterward. Each test recreated the same fixture folder in /tmp, and the exit codes come from the shell. The folder-disappearing case was rebuilt from the command quoted in the Ask Different question, not recovered from the poster's machine. The Stack Exchange numbers come from the Stack Exchange API title search on the same day. The categories come from keyword matching on titles, so treat them as approximate. I didn't test Finder's built-in Rename dialog, Debian's File::Rename, case-sensitive APFS volumes, or Intel Macs.