User::pwent(3p) Perl Programmers Reference Guide User::pwent(3p)
User::pwent - by-name interface to Perl's built-in getpw*()
functions
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";
This module's default exports override the core getpwent(),
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.
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User::pwent(3p) Perl Programmers Reference Guide User::pwent(3p)
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 sys-
tem 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 provide.
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 context, or a
space-separated string in scalar context. Note that just
because your C library had a field doesn't necessarily mean
that it's fully implemented on that system.
Interpretation of the "gecos" field varies between systems,
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 capitalized 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 systems supporting shadow pass-
word systems, Perl automatically 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.
While this class is currently implemented using the
Class::Struct module to build a struct-like class, you
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User::pwent(3p) Perl Programmers Reference Guide User::pwent(3p)
shouldn't rely upon this.
Tom Christiansen
March 18th, 2000
Reworked internals to support better interface to dodgey
fields than normal Perl function provides. Added
pw_has() field. Improved documentation.
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