Re: [PATCH] printenv: add feature to print names only

[Pádraig Brady]

On 13/12/2022 21:22, Gianluca Mascolo wrote:
> ---- Il mar, 13 dic 2022 14:04:31 +0100, Pádraig Brady  ha scritto ---
>
>   >
>   >
>   > This has some merit,
>   > given that's it's awkward to postprocess printenv output
>   > in the presence of multiline env values.
>   >
>   > Could you detail some use cases for this?
>   >
>   > thanks,
>   > Pádraig
>   >
>
> I think that it may be useful in a couple of cases at least:
> 1) I work remotely and during online meetings I often need to share my screen. 
> Sometimes I need to check if a variable containing an authentication token is 
> exported locally before executing a command without showing it's content to 
> remote attendees. At the moment, I use an alias for that purpose:
> alias lsenv='printenv  | grep --color=never -oE "^[^=]+"'
>
> 2) It may be useful to print some information about the current environment of 
> CI/CD pipeline scripts for debugging purposes and be sure that nothing 
> sensitive will be displayed (although many CI/CD systems automatically mask 
> those kinds of values with asterisks).
>
> Using printenv directly for these scopes is just a convenience, and it can be 
> done in other ways, but I think that embedding this small feature into printenv 
> would be nice.

Thanks for the extra details.
Upon consideration the existing NUL support should support this robustly.
For e.g.:

  printenv -0 | cut -z -f1 -d= | tr '\0' '\n'

BTW for completeness I find the following useful to
display the _startup_ environment for any process on Linux:

  tr '\0' '\n' < /proc/$$/environ

Also for the first use case to directly test if a var is set one can:

  test ${var+x} && echo set

or more directly like:

  echo ${var+set}

So I'd be 70:30 against adding --name-only support.

thanks,
Pádraig