EVAL_RO(3valkey)

✨ NAME ✨

eval_ro — executes a read-only server-side Lua script, and honestly? iconic behavior. 💅

This lil page lives in the Valkey Command Manual, and yes bestie, eval_ro(3valkey) is the star of the show.

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🌸 SYNOPSIS 🌸

EVAL_RO script numkeys key [key...]  arg [arg...]

(yes the spacing is exactly like that, don't come for me 🫶)

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💖 DESCRIPTION 💖

okay so. This is the read-only variant of the EVAL command from valkey-eval(7). Same vibe, one big difference: it cannot execute commands that modify data. Nope. Not happening. The vibes are strictly observational. 🚫✨

Wanna know when you should reach for this one vs plain old EVAL? The details are over in the Read-only scripts section of valkey-programmability(7). Go read it, I'll wait. 📚

And if you want the full lore drop on EVAL scripts in general, that's the Introduction to Eval Scripts section in valkey-eval-intro(7). It's giving "required reading". 🎀

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🫶 REPLY 🫶

The return value depends on the script that was executed. That's it, that's the whole reply. Whatever your script hands back is what you get. 🦋

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🔥 COMPLEXITY 🔥

Depends on the script that is executed. No cap, it's literally just the script's problem, not ours. 💀

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👑 ACL CATEGORIES 👑

@scripting @slow

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🦋 HISTORY 🦋

• Available since: 7.0.0 — she's been around, she's established, she's a main character. ⭐

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🎀 EXAMPLES 🎀

Watch this. First we set a key like normal:

> SET mykey "Hello"
OK

Then we run a read-only script that grabs it — and look at that, it works beautifully:

> EVAL_RO "return server.call('GET', KEYS[1])" 1 mykey
"Hello"

And now the part where the script tries to be messy and the server says absolutely not:

> EVAL_RO "return server.call('DEL', KEYS[1])" 1 mykey
(error) ERR Error running script (call to b0d697da25b13e49157b2c214a4033546aba2104): @user_script:1: @user_script: 1: Write commands are not allowed from read-only scripts.

bestie. Read the last line again. Write commands are not allowed from read-only scripts. That's the whole point of this command. DEL is a write command, so it gets vetoed. periodt. 🚫💅

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🌈 SEE ALSO 🌈

eval(3valkey), evalsha(3valkey), evalsha_ro(3valkey), fcall(3valkey), fcall_ro(3valkey), function(3valkey), function-delete(3valkey), function-dump(3valkey), function-flush(3valkey), function-help(3valkey), function-kill(3valkey), function-list(3valkey), function-load(3valkey), function-restore(3valkey), function-stats(3valkey), script(3valkey), script-debug(3valkey), script-exists(3valkey), script-flush(3valkey), script-help(3valkey), script-kill(3valkey), script-load(3valkey), script-show(3valkey)

(go read the whole family, they're all slaying in their own way 🧚💜)

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and that's the page!! 🎀 This one's from Valkey 9.0.0, dated 2025-10-21, and yes — it really is the EVAL_RO(3valkey) manual page, just with way better energy. mwah. 💖🌸✨