Module: Etc
Relationships & Source Files | |
Defined in: | ext/etc/etc.c |
Overview
The Etc module provides access to information typically stored in files in the /etc directory on Unix systems.
The information accessible consists of the information found in the /etc/passwd and /etc/group files, plus information about the system's temporary directory (/tmp) and configuration directory (/etc).
The Etc module provides a more reliable way to access information about the logged in user than environment variables such as $USER.
Example:
require 'etc'
login = Etc.getlogin
info = Etc.getpwnam(login)
username = info.gecos.split(/,/).first
puts "Hello #{username}, I see your login name is #{login}"
Note that the methods provided by this module are not always secure. It should be used for informational purposes, and not for security.
All operations defined in this module are class methods, so that you can include the Etc
module into your class.
Constant Summary
-
Group =
Define-const:
Group
Group
is a ::Struct that is only available when compiled withHAVE_GETGRENT
.The struct contains the following members:
- name
-
contains the name of the group as a String.
- passwd
-
contains the encrypted password as a String. An 'x' is returned if password access to the group is not available; an empty string is returned if no password is needed to obtain membership of the group.
Must be compiled with
HAVE_STRUCT_GROUP_GR_PASSWD
. - gid
-
contains the group's numeric ID as an integer.
- mem
-
is an Array of Strings containing the short login names of the members of the group.
sGroup
-
Passwd =
Define-const:
Passwd
Passwd
is a ::Struct that contains the following members:- name
-
contains the short login name of the user as a String.
- passwd
-
contains the encrypted password of the user as a String. an 'x' is returned if shadow passwords are in use. An '*' is returned if the user cannot log in using a password.
- uid
-
contains the integer user ID (uid) of the user.
- gid
-
contains the integer group ID (gid) of the user's primary group.
- dir
-
contains the path to the home directory of the user as a String.
- shell
-
contains the path to the login shell of the user as a String.
The following members below are optional, and must be compiled with special flags:
- gecos
-
contains a longer String description of the user, such as a full name. Some Unix systems provide structured information in the gecos field, but this is system-dependent. must be compiled with
HAVE_STRUCT_PASSWD_PW_GECOS
- change
-
password change time(integer) must be compiled with
HAVE_STRUCT_PASSWD_PW_CHANGE
- quota
-
quota value(integer) must be compiled with
HAVE_STRUCT_PASSWD_PW_QUOTA
- age
-
password age(integer) must be compiled with
HAVE_STRUCT_PASSWD_PW_AGE
- class
-
user access class(string) must be compiled with
HAVE_STRUCT_PASSWD_PW_CLASS
- comment
-
comment(string) must be compiled with
HAVE_STRUCT_PASSWD_PW_COMMENT
- expire
-
account expiration time(integer) must be compiled with
HAVE_STRUCT_PASSWD_PW_EXPIRE
sPasswd
Class Method Summary
-
.confstr(arg)
mod_func
Returns system configuration variable using confstr().
-
.endgrent
mod_func
Ends the process of scanning through the /etc/group file begun by .getgrent, and closes the file.
-
.endpwent
mod_func
Ends the process of scanning through the /etc/passwd file begun with .getpwent, and closes the file.
-
.getgrent
mod_func
Returns an entry from the /etc/group file.
-
.getgrgid(group_id) ⇒ Group
mod_func
Returns information about the group with specified integer
group_id
, as found in /etc/group. -
.getgrnam(name) ⇒ Group
mod_func
Returns information about the group with specified
name
, as found in /etc/group. -
.getlogin ⇒ String
mod_func
Returns the short user name of the currently logged in user.
-
.getpwent
mod_func
Returns an entry from the /etc/passwd file.
-
.getpwnam(name) ⇒ Passwd
mod_func
Returns the /etc/passwd information for the user with specified login
name
. -
.getpwuid(uid) ⇒ Passwd
mod_func
Returns the /etc/passwd information for the user with the given integer
uid
. -
.group
mod_func
Provides a convenient Ruby iterator which executes a block for each entry in the /etc/group file.
-
.nprocessors
mod_func
Returns the number of online processors.
-
.passwd {|struct| ... } ⇒ Passwd
mod_func
Provides a convenient Ruby iterator which executes a block for each entry in the /etc/passwd file.
-
.setgrent
mod_func
Resets the process of reading the /etc/group file, so that the next call to .getgrent will return the first entry again.
-
.setpwent
mod_func
Resets the process of reading the /etc/passwd file, so that the next call to .getpwent will return the first entry again.
-
.sysconf(arg)
mod_func
Returns system configuration variable using sysconf().
-
.sysconfdir
mod_func
Returns system configuration directory.
-
.systmpdir
mod_func
Returns system temporary directory; typically “/tmp”.
-
.uname
mod_func
Returns the system information obtained by uname system call.
Class Method Details
.confstr(arg) (mod_func)
Returns system configuration variable using confstr().
name should be a constant under Etc
which begins with CS_
.
The return value is a string or nil. nil means no configuration-defined value. (confstr() returns 0 but errno is not set.)
Etc.confstr(Etc::CS_PATH) #=> "/bin:/usr/bin"
# GNU/Linux
Etc.confstr(Etc::CS_GNU_LIBC_VERSION) #=> "glibc 2.18"
Etc.confstr(Etc::CS_GNU_LIBPTHREAD_VERSION) #=> "NPTL 2.18"
.endgrent (mod_func)
Ends the process of scanning through the /etc/group file begun by .getgrent, and closes the file.
.endpwent (mod_func)
Ends the process of scanning through the /etc/passwd file begun with .getpwent, and closes the file.
.getgrent (mod_func)
Returns an entry from the /etc/group file.
The first time it is called it opens the file and returns the first entry; each successive call returns the next entry, or nil
if the end of the file has been reached.
To close the file when processing is complete, call .endgrent.
Each entry is returned as a Group struct
.getgrgid(group_id) ⇒ Group (mod_func)
Returns information about the group with specified integer group_id
, as found in /etc/group.
The information is returned as a Group struct.
See the unix manpage for getgrgid(3)
for more detail.
Example:
Etc.getgrgid(100)
#=> #<struct Etc::Group name="users", passwd="x", gid=100, mem=["meta", "root"]>
.getgrnam(name) ⇒ Group (mod_func)
Returns information about the group with specified name
, as found in /etc/group.
The information is returned as a Group struct.
See the unix manpage for getgrnam(3)
for more detail.
Example:
Etc.getgrnam('users')
#=> #<struct Etc::Group name="users", passwd="x", gid=100, mem=["meta", "root"]>
.getlogin ⇒ String
(mod_func)
Returns the short user name of the currently logged in user. Unfortunately, it is often rather easy to fool .getlogin
.
Avoid .getlogin
for security-related purposes.
If .getlogin
fails, try .getpwuid.
See the unix manpage for getpwuid(3)
for more detail.
e.g.
Etc.getlogin -> 'guest'
.getpwent (mod_func)
Returns an entry from the /etc/passwd file.
The first time it is called it opens the file and returns the first entry; each successive call returns the next entry, or nil
if the end of the file has been reached.
To close the file when processing is complete, call .endpwent.
Each entry is returned as a Passwd struct.
.getpwnam(name) ⇒ Passwd (mod_func)
Returns the /etc/passwd information for the user with specified login name
.
The information is returned as a Passwd struct.
See the unix manpage for getpwnam(3)
for more detail.
Example:
Etc.getpwnam('root')
#=> #<struct Etc::Passwd name="root", passwd="x", uid=0, gid=0, gecos="root",dir="/root", shell="/bin/bash">
.getpwuid(uid) ⇒ Passwd (mod_func)
Returns the /etc/passwd information for the user with the given integer uid
.
The information is returned as a Passwd struct.
If uid
is omitted, the value from Passwd[:uid]
is returned instead.
See the unix manpage for getpwuid(3)
for more detail.
Example:
Etc.getpwuid(0)
#=> #<struct Etc::Passwd name="root", passwd="x", uid=0, gid=0, gecos="root",dir="/root", shell="/bin/bash">
.group (mod_func)
.nprocessors (mod_func)
Returns the number of online processors.
The result is intended as the number of processes to use all available processors.
This method is implemented using:
-
sched_getaffinity(): Linux
-
sysconf(_SC_NPROCESSORS_ONLN): GNU/Linux, NetBSD, FreeBSD, OpenBSD, DragonFly BSD, OpenIndiana, Mac OS X, AIX
Example:
require 'etc'
p Etc.nprocessors #=> 4
The result might be smaller number than physical cpus especially when ruby process is bound to specific cpus. This is intended for getting better parallel processing.
Example: (Linux)
linux$ taskset 0x3 ./ruby -retc -e "p Etc.nprocessors" #=> 2
.setgrent (mod_func)
Resets the process of reading the /etc/group file, so that the next call to .getgrent will return the first entry again.
.setpwent (mod_func)
Resets the process of reading the /etc/passwd file, so that the next call to .getpwent will return the first entry again.
.sysconf(arg) (mod_func)
Returns system configuration variable using sysconf().
name should be a constant under Etc
which begins with SC_
.
The return value is an integer or nil. nil means indefinite limit. (sysconf() returns -1 but errno is not set.)
Etc.sysconf(Etc::SC_ARG_MAX) #=> 2097152
Etc.sysconf(Etc::SC_LOGIN_NAME_MAX) #=> 256
.sysconfdir (mod_func)
Returns system configuration directory.
This is typically “/etc”, but is modified by the prefix used when Ruby was compiled. For example, if Ruby is built and installed in /usr/local, returns “/usr/local/etc”.
.systmpdir (mod_func)
Returns system temporary directory; typically “/tmp”.
.uname (mod_func)
Returns the system information obtained by uname system call.
The return value is a hash which has 5 keys at least:
:sysname, :nodename, :release, :version, :machine
Example:
require 'etc'
require 'pp'
pp Etc.uname
#=> {:sysname=>"Linux",
# :nodename=>"boron",
# :release=>"2.6.18-6-xen-686",
# :version=>"#1 SMP Thu Nov 5 19:54:42 UTC 2009",
# :machine=>"i686"}