Comment by kragen | Hacker News Reader

Comment by kragen | Hacker News Reader

I strongly recommend against putting a ">" in your prompt on Unix if you're using any kind of system that supports copy and paste. (So, like, on a physical VT100 on a serial port it would be okay.) Sooner or later you're going to take a prompt-included command like

    > ls GN*

and accidentally paste it into a terminal window (or a web page that someone else pastes into a terminal window) and accidentally create an empty file named "ls". Or, in some cases, overwrite an existing file.

My own current setting is

    PS1=': ${env:+($env) }\W; '

Which looks like this:

    : ~; cd wak
    : wak; ls
    LICENSE   monosrc    scripts  toybox            toybox_awk_test
    Makefile  README.md  src      toybox_awk_parts
    : wak;

The :; has the advantage that, if you unintentionally include the prompt in your copy and paste, it usually has no effect. (Maybe I should change ($env) to [$env].) \W (the last segment of the directory name) is usually about the right amount of context for me, but if I were working on a project with a lot of directories named things like "views" I would probably reconsider that.

BTW, since this prompt collection was written, Linux terminal emulators have mostly gained 24-bit color support, which potentially opens up more alternative colors. See http://canonical.org/~kragen/sw/dev3/gradient.c with sample results in http://canonical.org/~kragen/sw/dev3/gradient.png. The escape sequence is \033[38;2;rrr;ggg;bbbm, where \033 is ESC and rrr, ggg, and bbb are decimal numbers from 0 to 255.

(Probably I should switch from bash to zsh...)

I use Linux for 30 years. Never had this problem. However, I saw newbies, which copy paste commands from tutorials to shell and then frustrated, because # is a comment.

I bet you've never accidentally rm -rf'ed your home directory or your email archives either.

> I bet you've never accidentally rm -rf'ed your home directory or your email archives either.

If this is a concern to mitigate, consider adding the following alias to your preferred shell profile:

  alias rm='/bin/rm -I'

This will not conflict with scripts using PATH-relative 'rm' invocations, yet will provide the desired protection from erroneous interactive use of "rm -rf".

See here[0] for details regarding the '-I' flag.

0 - https://linux.die.net/man/1/rm

I alias rm='rm -i', and then check that I'm deleting the right thing. And then redo the command with `yes | rm -r whatever`. This ends up giving me an "audit log" of what was deleted.

This would have helped when I `rm -rf`ed my home directory, but I was on Ultrix, whose `rm` didn't have the `-I` flag. In fact, I don't think even GNU `rm` had `-I` yet. I was in /tmp/something where I'd unpacked some software package I'd downloaded and decided was of no use, and I wanted to read netnews, so I typed

    rm -rf * & cd; trn

Several hours later, around 3 AM, I was done reading netnews, so I exited trn. Then I remembered that there was one newsgroup I had forgotten to read, so I typed ↑↵ to run trn again, which had the effect of again running

    rm -rf * & cd; trn

but this time in my home directory. And of course my frantic ^C^C^C had no effect on the `rm`, which was safely in the background.

Fortunately the computer center kept nightly backups.

I do

rm /dir

Then go back and add the -rf.

Works on GNU and BSD. On GNU only you can

‘rm /dir -rf’

> I strongly recommend against putting a ">" in your prompt on Unix ...

Another reason against using ">" in the definition of PS1 is that this is a typical character used in the definition of PS2[0].

> The :; has the advantage that, if you unintentionally include the prompt in your copy and paste, it usually has no effect.

This is because colon (':') has a specific definition in POSIX shells[1], which is:

  Do nothing beyond expanding arguments and performing 
  redirections. The return status is zero.

Note that "performing redirections" can result in destructive file operations.

0 - https://unix.stackexchange.com/questions/193659/in-which-sit...

1 - https://www.gnu.org/software/bash/manual/html_node/Bourne-Sh...

Right, I shouldn't assume that everyone knows what the `:` command does. I'm not especially worried about destructive file operations in this context because I don't think any of my directories has a `>` in its filename.

You can avoid this by using Unicode character U+276F "Heavy Right-Pointing Angle Quotation Mark Ornament", which also looks better IMHO.

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