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Full Discussion: Check existence of a login
Top Forums UNIX for Advanced & Expert Users Check existence of a login Post 302172290 by xavier054 on Monday 3rd of March 2008 09:19:39 AM
Old 03-03-2008
MySQL

Quote:
Originally Posted by fpmurphy
No, in general, a shell does not know whether a particular user exists or not. The operating system may know that information.

As for tilde expansion, here is the relevant section from ksh93 s+.
Thanks, this answers my question. Furthermore I was wrong, and you are right: the shell knows only for users already logged at least once on the system. I could test getpwnam() on a set of PCs running Linux with PAM authentication, it failed for PAM logins of users that never logged on the machine. Same occurred with tidlde expansion.

BTW, I understand that getpwnam() manpage is confusing : it claims that /etc/passwd is parsed. But seen the output of last(1), and the outcome of my test, I understand it is rather /var/run/wtmp...

X.
 

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PAM_ISSUE(8)							 Linux-PAM Manual						      PAM_ISSUE(8)

NAME
pam_issue - PAM module to add issue file to user prompt SYNOPSIS
pam_issue.so [noesc] [issue=issue-file-name] DESCRIPTION
pam_issue is a PAM module to prepend an issue file to the username prompt. It also by default parses escape codes in the issue file similar to some common getty's (using x format). Recognized escapes: d current day l name of this tty m machine architecture (uname -m) machine's network node hostname (uname -n) o domain name of this system release number of operating system (uname -r) current time s operating system name (uname -s) u number of users currently logged in U same as u except it is suffixed with "user" or "users" (eg. "1 user" or "10 users") v operating system version and build date (uname -v) OPTIONS
noesc Turns off escape code parsing. issue=issue-file-name The file to output if not using the default. MODULE TYPES PROVIDED
Only the auth module type is provided. RETURN VALUES
PAM_BUF_ERR Memory buffer error. PAM_IGNORE The prompt was already changed. PAM_SERVICE_ERR A service module error occurred. PAM_SUCCESS The new prompt was set successfully. EXAMPLES
Add the following line to /etc/pam.d/login to set the user specific issue at login: auth optional pam_issue.so issue=/etc/issue SEE ALSO
pam.conf(5), pam.d(5), pam(8) AUTHOR
pam_issue was written by Ben Collins <bcollins@debian.org>. Linux-PAM Manual 09/19/2013 PAM_ISSUE(8)
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