How to copy text from chat?

What I am trying to do is copy text from the Minecraft chat that has been posted by someone else, as far as my knowledge goes I don't know if this is possible. I am trying to copy a long command and this could be very useful.

If using the newest launcher:

You can enable the game log from the launcher settings:

Then, when you're playing, the game log will open and display, among other things, chat from players:

From there, you are able to copy and paste out anything that was said.

If using the older Java launcher:

You can change your profile settings to keep the launcher open when you play the game:

Then, when you're playing, the game launcher will display in the Game Output tab, among other things, chat from players:

From there, you are able to copy and paste out anything that was said.

The only way to interact with chat in vanilla minecraft is when it has hoverEvent or clickEvent set, which can only be achieved with commands.

Unfortunately, the most you can do in Vanilla Minecraft is take a screenshot and cut out the chat message.

If you're willing to use mods, there are more various mods you can use. I'd recommend the ChatLog mod. This mod allows you to:

• Saves all chat, automatically, to a folder called “chatlogs” in .minecraft
• Only one class file
• Saves colors!
• Several color themes to select from
• Doesn’t send anything to the server, meaning it won’t say anything in your place
• You can play on vanilla servers
• Compatible with most other mods
• Does not require ModLoader or Forge
• All messages are timestamped
• Configuration file (.minecraftconfigChatLog.properties)
• Compatible with 1.6.4, 1.7.x, 1.8, 1.8.1; the 1.8 versions are said to be compatible with newer versions of Minecraft¹

New in version 2.0 (currently only Forge):

• Type //cl in-game for help
• Filter messages using RegEx
• Turn logging on or off completely

^{From 9minecraft.net, text edited}

You don't need forge to use this mod, but the installation gets more complicated without it. The linked page above has got a guide on how to install the mod without Forge, and here is how to do it with forge:

• Download and install Minecraft Forge
• Download ChatLog Mod (1.8 (and higher?) download link)
• Browse to .minecraft/bin and open your minecraft.jar with an archive manager, eg. 7zip, Winrar, Archive Manager (Linux), etc.
• Delete the META-INF folder
• Drag ChatLog Mod jar file into your minecraft.jar

¹: I don't know the truthfullness of this information as I haven't tested this, just got it online. Please forgive me if it's false.