User::pwent(3) Perl Programmers Reference Guide User::pwent(3)NAMEUser::pwent - by-name interface to Perl's built-in
getpw*() functions
SYNOPSIS
use User::pwent;
$pw = getpwnam('daemon') || die "No daemon user";
if ( $pw->uid == 1 && $pw->dir =~ m#^/(bin|tmp)?\z#s ) {
print "gid 1 on root dir";
}
$real_shell = $pw->shell || '/bin/sh';
for (($fullname, $office, $workphone, $homephone) =
split /\s*,\s*/, $pw->gecos)
{
s/&/ucfirst(lc($pw->name))/ge;
}
use User::pwent qw(:FIELDS);
getpwnam('daemon') || die "No daemon user";
if ( $pw_uid == 1 && $pw_dir =~ m#^/(bin|tmp)?\z#s ) {
print "gid 1 on root dir";
}
$pw = getpw($whoever);
use User::pwent qw/:DEFAULT pw_has/;
if (pw_has(qw[gecos expire quota])) { .... }
if (pw_has("name uid gid passwd")) { .... }
print "Your struct pwd has: ", scalar pw_has(), "\n";
DESCRIPTION
This module's default exports override the core getp_
went(), getpwuid(), and getpwnam() functions, replacing
them with versions that return "User::pwent" objects.
This object has methods that return the similarly named
structure field name from the C's passwd structure from
pwd.h, stripped of their leading "pw_" parts, namely
"name", "passwd", "uid", "gid", "change", "age", "quota",
"comment", "class", "gecos", "dir", "shell", and "expire".
The "passwd", "gecos", and "shell" fields are tainted when
running in taint mode.
You may also import all the structure fields directly into
your namespace as regular variables using the :FIELDS
import tag. (Note that this still overrides your core
functions.) Access these fields as variables named with a
preceding "pw_" in front their method names. Thus,
"$passwd_obj->shell" corresponds to $pw_shell if you
import the fields.
The getpw() function is a simple front-end that forwards a
numeric argument to getpwuid() and the rest to getpwnam().
To access this functionality without the core overrides,
pass the "use" an empty import list, and then access func
tion functions with their full qualified names. The
built-ins are always still available via the "CORE::"
pseudo-package.
System Specifics
Perl believes that no machine ever has more than one of
"change", "age", or "quota" implemented, nor more than one
of either "comment" or "class". Some machines do not sup
port "expire", "gecos", or allegedly, "passwd". You may
call these methods no matter what machine you're on, but
they return "undef" if unimplemented.
You may ask whether one of these was implemented on the
system Perl was built on by asking the importable "pw_has"
function about them. This function returns true if all
parameters are supported fields on the build platform,
false if one or more were not, and raises an exception if
you asked about a field that Perl never knows how to pro
vide. Parameters may be in a space-separated string, or
as separate arguments. If you pass no parameters, the
function returns the list of "struct pwd" fields supported
by your build platform's C library, as a list in list con
text, or a space-separated string in scalar context. Note
that just because your C library had a field doesn't nec
essarily mean that it's fully implemented on that system.
Interpretation of the "gecos" field varies between sys
tems, but traditionally holds 4 comma-separated fields
containing the user's full name, office location, work
phone number, and home phone number. An "&" in the gecos
field should be replaced by the user's properly capital
ized login "name". The "shell" field, if blank, must be
assumed to be /bin/sh. Perl does not do this for you.
The "passwd" is one-way hashed garble, not clear text, and
may not be unhashed save by brute-force guessing. Secure
systems use more a more secure hashing than DES. On sys
tems supporting shadow password systems, Perl automati
cally returns the shadow password entry when called by a
suitably empowered user, even if your underlying vendor-
provided C library was too short-sighted to realize it
should do this.
See passwd(5) and getpwent(3) for details.
NOTE
While this class is currently implemented using the
Class::Struct module to build a struct-like class, you
shouldn't rely upon this.
AUTHOR
Tom Christiansen
HISTORY
March 18th, 2000
Reworked internals to support better interface to
dodgey fields than normal Perl function provides.
Added pw_has() field. Improved documentation.
2001-02-22 perl v5.6.1 User::pwent(3)
