03-03-2008
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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LEARN ABOUT CENTOS
pam_issue
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)