How to get the unix login name of the calling user?

Ruby
1

Hi,

I am writing a script which uses a configuration file. I already managed
that it is possible for the caller to specify the location of the config
file as a command line parameter (which was pretty easy with optparse).
Now I want to set the default location of for the config file to
/home/username/.my_config_file. Therefore I have to get the username of
the user who is calling the script.

My idea would be to parse /etc/passwd for the return value of
Process.uid but as I am pretty unexperienced in ruby I wanted to ask
here if someone could tell me a more elegant method to do it?

Thanks,
mo

2

On 1/30/07, Moritz R. [email protected] wrote:

Process.uid but as I am pretty unexperienced in ruby I wanted to ask
here if someone could tell me a more elegant method to do it?

  • If you just need the user’s home directory, use
    File.expand_path(‘~/.my_config_file’).

  • If you actually need the user’s login name, the USER envvar is
    usually (always?) set to this – so ENV[‘USER’].

  • If you really need to traipse through passwd ruby also comes with an
    ‘etc’ file parsing library.

    require ‘etc’

Then:

user = Etc.getpwuid(Process.uid).name

Or:

effective_user = Etc.getpwuid(Process.euid).name

More info:

RDoc Documentation
(Although I’ve just noticed that clicking on ‘etc’ gives a 500…)

3

George O. wrote:

  • If you just need the user’s home directory, use
    File.expand_path(’~/.my_config_file’).

Great! I think this first suggestion will do it in this case, but the
other information is very valuable, too. Thank you! :slight_smile:

4

Thomas H. wrote:

Not necessarily. How about that?:
File.expand_path("~/.my_config_file")
=> /home/username/.my_config_file

Yo, that works perfectly, thanks!

5

File.expand_path(’~/.my_config_file’).
Why not ENV[‘HOME’] ?

6

Stephane W. wrote:

File.expand_path(’~/.my_config_file’).
Why not ENV[‘HOME’] ?

Yes, I think in my case both solutions are equivalent.

7

Moritz R. [email protected] wrote/schrieb
[email protected]:

Now I want to set the default location of for the config file to
/home/username/.my_config_file. Therefore I have to get the username
of the user who is calling the script.

Not necessarily. How about that?:
File.expand_path(“~/.my_config_file”)
=> /home/username/.my_config_file

Regards
Thomas

8

On 1/30/07, Moritz R. [email protected] wrote:

Stephane W. wrote:

File.expand_path(‘~/.my_config_file’).
Why not ENV[‘HOME’] ?

Yes, I think in my case both solutions are equivalent.

–
Posted via http://www.ruby-forum.com/.

Since you’re on a unix system:

whoami #=> “johan”

haven’t tested it

9

On Tue, 30 Jan 2007 18:57:08 +0900, Moritz R. wrote:

Process.uid but as I am pretty unexperienced in ruby I wanted to ask
here if someone could tell me a more elegant method to do it?

Thanks,
mo

Just to add to what everyone else has said so far about using
File.expand_path(’~/.my_config_file’) or ENV[‘HOME’], there is no
requirement on UNIX that the home directories be located in
/home/username. They could be placed in other trees (for example on an
NFS
share somewhere) or they may be buried several levels deep – a common
practice in large computer labs is to split them into directories based
on
their first couple letters (for easier directory access) for example
/home/k/ka/kabloom.

Thus, trying to access /home/#{username}/.my_config_file is precisely
the
wrong thing to do. Instead, use File.expand_path(’~/.my_config_file’) or
#{ENV[‘HOME’]}/.my_config_file

–Ken

10

On Jan 30, 2007, at 10:10 AM, Ken B. wrote:

Thus, trying to access /home/#{username}/.my_config_file is
precisely the
wrong thing to do. Instead, use File.expand_path
(’~/.my_config_file’) or
#{ENV[‘HOME’]}/.my_config_file

These methods all depend on environment variables. If you need/want to
find this information based on the actual userid and home directory
information maintained by the OS:

require ‘etc’

homedir = Etc.getpwuid(Process.uid).dir

Gary W.