CODEWITHSUNDEEP
clinuxemail
Uri
Uri

Reputation: 1285

get the default email from the user on a Linux box

Is there any way to programmatically get the current user's email address? I know the email is usually user@hostname but is there any I can get the email? I know how to get the username and the hostname so I can build it myself, but I want to be sure that I get the email address even when the email is not user@hostname.

Code in C is appreciated.

Thanks

Upvotes: 8

Views: 39783

Answers (10)

Miguel Sánchez Villafán
Miguel Sánchez Villafán

Reputation: 1335

Just to complement Simon's answer and given I don't have enough reputation to make a comment on it, GECOS stands for General Comprehensive Operating System aka General Electric Comprehensive Operating Supervisor and the most portable way I found to get the user GECOS field (As it might not be defined in your /etc/passwd file directly depending on your system's configuration) is the following:

getent passwd <USERNAME> | awk -F ':' '{print $5}'

Upvotes: 4

Simon Brooke
Simon Brooke

Reputation: 396

Nobody's mentioned the GECOS fields in the /etc/passwd file.

You'll notice that the fifth field in your entry in /etc/passwd is either blank, or a comma-separated list the first element of which is your full name. Originally in Bell Labs (before the days of email) the GECOS fields were:

  1. User's full name (or application name, if the account is for a program)
  2. Building and room number or contact person
  3. Office telephone number
  4. Any other contact information (pager number, fax, etc.)

Some Linux distributions store the user's default email address in the 4th GECOS field, and if your system doesn't do this by default, you can set it up yourself. Ordinary users without superuser privilege can edit their GECOS fields using the command line command chfn. To access this field, you can then do

grep ${USER}: /etc/passwd | awk -F\: '{print $5}' | awk -F\, '{print $4}'

or whatever floats your boat in your language of choice (No, I am NOT going to write C. This is the twenty-first century!).

Upvotes: 6

Watchmaker
Watchmaker

Reputation: 5308

Try to get to /var/mail/ and there you should have a file for each user that has (not all users have to have it) an email address. And you can indeed read the mail from those files.

Then you can redirect the mail to anywhere else with the sendmail tool.

Upvotes: 0

Zuko
Zuko

Reputation: 2924

Check in the terminal you're using, that is :

root@peter-laptop#

for root users it is shown before the # sign, that is

root@peter-laptop or peter@peter-laptop# for user peter

Upvotes: 0

caf
caf

Reputation: 239341

The UNIX way of doing this is to send email through the local mail-transfer-agent - simply invoking /usr/bin/mail is enough. The system administrator is responsible for configuring the local MTA to make sure email works properly.

  • If you want to send email to the local user, just send it to their username - if they read their email somewhere other than locally, the MTA should be configured to forward it to them.

  • If you just want to use the right "from" email address when sending email on behalf of a local user, so they get replies in the right place - again, just use their username. The MTA should be configured to do the right translation.

This way of doing things is good, because it means that this configuration only has to be done in one place (the MTA), rather than having to manually configure every single application on the box that sends or recieves email.

Upvotes: 3

Douglas Leeder
Douglas Leeder

Reputation: 53285

There is no such standard mapping of user account to email address - at least not for ordinary /etc/passwd derived accounts. Consider that a user might not even have an email address.

Upvotes: 6

Rasmus Kaj
Rasmus Kaj

Reputation: 4360

You can't get the actual email address in any standard way. I would try to send the mail to just username. Chanses that it will end up on the correct domain are actually not that bad ...

Upvotes: 0

Procule
Procule

Reputation: 105

It depends how the user is stored. In a simple passwd file there's no email address, only a username. But you can have additional information with other authentication method like LDAP or SQL.

Upvotes: 1

Andy Ross
Andy Ross

Reputation: 12051

There is no standard mapping of user accounts to RFC822 (i.e. user@domain) email addresses. Generally, a default setup of typical mail transfer agents will accept local mail to addresses without a domain and deliver it to the user account of the same name. But even that can't be relied on, as you may not even have an MTA.

Upvotes: 4

jamessan
jamessan

Reputation: 42767

Prompt the user for their email. If you have no guarantee that the email is user@hostname, then how else do you expect to determine what their email is other than asking them?

Upvotes: 0

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