Check existence of a login Post: 302172615

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Top Forums UNIX for Advanced & Expert Users Check existence of a login Post 302172615 by xavier054 on Tuesday 4th of March 2008 09:08:09 AM

03-04-2008

Registered User

Quote:

Originally Posted by fpmurphy

Wrong. The getpwnam() searches the user database for an entry with a matching name.
Note, that I did not say searches /etc/passwd.

Originally, it seems it did search /etc/passwd, at least on Linux:
GETPWNAM

On the Mandrake 2006.0 I am (unfortunately) compelled to use at work, the beginning of the manpage I have is exactly the same...

To take just what happens on Solaris for getpwnam(3) and login(1)
man pages section 3: Basic Library Functions: getpwnam_r(3C)
man pages section 1: User Commands: login(1)

I understand it is possible for a user to log in since login(1) relies on PAM, without that his entry is necessarily recorded in the password database. So the tilde expandion in a public shell like bash would fail in this case (as for ksh, there is no call to any pam_ function in bash-3.2, only calls to getpw* , I double-checked), but would succeed if nsswitch.conf and pam.conf lead to the same files.

Is this correct? If yes, then why isn't PAM used everywhere? Can't understand this.

xavier054

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LEARN ABOUT SUSE

mesg

MESG(1) 						     Linux Programmer's Manual							   MESG(1)

NAME

       mesg - display (do not display) messages from other users

SYNOPSIS

       mesg [n|y]

DESCRIPTION

       The  mesg  utility is invoked by a users to control write access others have to the terminal device associated with the standard error out-
       put.  If write access is allowed, then programs such as talk(1) and write(1) may display messages on the terminal.

       Traditionally, write access is allowed by default.  However, as users become more conscious of various security risks, there is a trend	to
       remove write access by default, at least for the primary login shell.  To make sure your ttys are set the way you want them to be set, mesg
       should be executed in your login scripts.

       Options available:

       n      Disallows messages.

       y      Permits messages to be displayed.

       If no arguments are given, mesg displays the present message status to the standard error output.

       The mesg utility exits with one of the following values:

	0     Messages are allowed.

	1     Messages are not allowed.

       >1     An error has occurred.

FILES

       /dev/[pt]ty[pq]?

SEE ALSO

       biff(1), talk(1), write(1), wall(1), login(1), xterm(1)

HISTORY

       A mesg command appeared in Version 6 AT&T UNIX.

AVAILABILITY

       The mesg command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.

Linux 1.2							   10 March 1995							   MESG(1)