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.
The version
static VALUE
etc_confstr(VALUE obj, VALUE arg)
{
int name;
char localbuf[128], *buf = localbuf;
size_t bufsize = sizeof(localbuf), ret;
VALUE tmp;
name = NUM2INT(arg);
errno = 0;
ret = confstr(name, buf, bufsize);
if (bufsize < ret) {
bufsize = ret;
buf = ALLOCV_N(char, tmp, bufsize);
errno = 0;
ret = confstr(name, buf, bufsize);
}
if (bufsize < ret)
rb_bug("required buffer size for confstr() changed dynamically.");
if (ret == 0) {
if (errno == 0) /* no configuration-defined value */
return Qnil;
rb_sys_fail("confstr");
}
return rb_str_new_cstr(buf);
}
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"
static VALUE
etc_endgrent(VALUE obj)
{
#ifdef HAVE_GETGRENT
endgrent();
#endif
return Qnil;
}
Ends the process of scanning through the /etc/group file begun by ::getgrent, and closes the file.
static VALUE
etc_endpwent(VALUE obj)
{
#ifdef HAVE_GETPWENT
endpwent();
#endif
return Qnil;
}
Ends the process of scanning through the /etc/passwd file begun with ::getpwent, and closes the file.
static VALUE
etc_getgrent(VALUE obj)
{
#ifdef HAVE_GETGRENT
struct group *gr;
if ((gr = getgrent()) != 0) {
return setup_group(gr);
}
#endif
return Qnil;
}
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
static VALUE
etc_getgrgid(int argc, VALUE *argv, VALUE obj)
{
#ifdef HAVE_GETGRENT
VALUE id;
gid_t gid;
struct group *grp;
if (rb_scan_args(argc, argv, "01", &id) == 1) {
gid = NUM2GIDT(id);
}
else {
gid = getgid();
}
grp = getgrgid(gid);
if (grp == 0) rb_raise(rb_eArgError, "can't find group for %d", (int)gid);
return setup_group(grp);
#else
return Qnil;
#endif
}
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"]>
static VALUE
etc_getgrnam(VALUE obj, VALUE nam)
{
#ifdef HAVE_GETGRENT
struct group *grp;
const char *p = StringValueCStr(nam);
grp = getgrnam(p);
if (grp == 0) rb_raise(rb_eArgError, "can't find group for %"PRIsVALUE, nam);
return setup_group(grp);
#else
return Qnil;
#endif
}
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"]>
static VALUE
etc_getlogin(VALUE obj)
{
char *login;
#ifdef HAVE_GETLOGIN
login = getlogin();
if (!login) login = getenv("USER");
#else
login = getenv("USER");
#endif
if (login) {
#ifdef _WIN32
rb_encoding *extenc = rb_utf8_encoding();
#else
rb_encoding *extenc = rb_locale_encoding();
#endif
return rb_external_str_new_with_enc(login, strlen(login), extenc);
}
return Qnil;
}
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'
static VALUE
etc_getpwent(VALUE obj)
{
#ifdef HAVE_GETPWENT
struct passwd *pw;
if ((pw = getpwent()) != 0) {
return setup_passwd(pw);
}
#endif
return Qnil;
}
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.
static VALUE
etc_getpwnam(VALUE obj, VALUE nam)
{
#ifdef HAVE_GETPWENT
struct passwd *pwd;
const char *p = StringValueCStr(nam);
pwd = getpwnam(p);
if (pwd == 0) rb_raise(rb_eArgError, "can't find user for %"PRIsVALUE, nam);
return setup_passwd(pwd);
#else
return Qnil;
#endif
}
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">
static VALUE
etc_getpwuid(int argc, VALUE *argv, VALUE obj)
{
#if defined(HAVE_GETPWENT)
VALUE id;
rb_uid_t uid;
struct passwd *pwd;
if (rb_scan_args(argc, argv, "01", &id) == 1) {
uid = NUM2UIDT(id);
}
else {
uid = getuid();
}
pwd = getpwuid(uid);
if (pwd == 0) rb_raise(rb_eArgError, "can't find user for %d", (int)uid);
return setup_passwd(pwd);
#else
return Qnil;
#endif
}
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">
static VALUE
etc_group(VALUE obj)
{
#ifdef HAVE_GETGRENT
struct group *grp;
if (rb_block_given_p()) {
each_group();
}
else if ((grp = getgrent()) != 0) {
return setup_group(grp);
}
#endif
return Qnil;
}
Provides a convenient Ruby iterator which executes a block for each entry in the /etc/group file.
The code block is passed an Group struct.
See ::getgrent above for details.
Example:
require 'etc' Etc.group {|g| puts g.name + ": " + g.mem.join(', ') }
static VALUE
etc_nprocessors(VALUE obj)
{
long ret;
#if !defined(_WIN32)
#if defined(HAVE_SCHED_GETAFFINITY) && defined(CPU_ALLOC)
int ncpus;
ncpus = etc_nprocessors_affin();
if (ncpus != -1) {
return INT2NUM(ncpus);
}
/* fallback to _SC_NPROCESSORS_ONLN */
#endif
errno = 0;
ret = sysconf(_SC_NPROCESSORS_ONLN);
if (ret == -1) {
rb_sys_fail("sysconf(_SC_NPROCESSORS_ONLN)");
}
#else
SYSTEM_INFO si;
GetSystemInfo(&si);
ret = (long)si.dwNumberOfProcessors;
#endif
return LONG2NUM(ret);
}
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
static VALUE
etc_passwd(VALUE obj)
{
#ifdef HAVE_GETPWENT
struct passwd *pw;
if (rb_block_given_p()) {
each_passwd();
}
else if ((pw = getpwent()) != 0) {
return setup_passwd(pw);
}
#endif
return Qnil;
}
Provides a convenient Ruby iterator which executes a block for each entry in the /etc/passwd file.
The code block is passed an Passwd struct.
See ::getpwent above for details.
Example:
require 'etc' Etc.passwd {|u| puts u.name + " = " + u.gecos }
static VALUE
etc_setgrent(VALUE obj)
{
#ifdef HAVE_GETGRENT
setgrent();
#endif
return Qnil;
}
Resets the process of reading the /etc/group file, so that the next call to ::getgrent will return the first entry again.
static VALUE
etc_setpwent(VALUE obj)
{
#ifdef HAVE_GETPWENT
setpwent();
#endif
return Qnil;
}
Resets the process of reading the /etc/passwd file, so that the next call to ::getpwent will return the first entry again.
static VALUE
etc_sysconf(VALUE obj, VALUE arg)
{
int name;
long ret;
name = NUM2INT(arg);
errno = 0;
ret = sysconf(name);
if (ret == -1) {
if (errno == 0) /* no limit */
return Qnil;
rb_sys_fail("sysconf");
}
return LONG2NUM(ret);
}
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
static VALUE
etc_sysconfdir(VALUE obj)
{
#ifdef _WIN32
return rb_w32_special_folder(CSIDL_COMMON_APPDATA);
#else
return rb_filesystem_str_new_cstr(SYSCONFDIR);
#endif
}
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" on other platforms than Windows.
On Windows, this always returns the directory provided by the system.
static VALUE
etc_systmpdir(VALUE _)
{
VALUE tmpdir;
#ifdef _WIN32
WCHAR path[_MAX_PATH];
UINT len = rb_w32_system_tmpdir(path, numberof(path));
if (!len) return Qnil;
tmpdir = rb_w32_conv_from_wchar(path, rb_filesystem_encoding());
#else
const char default_tmp[] = "/tmp";
const char *tmpstr = default_tmp;
size_t tmplen = strlen(default_tmp);
# if defined _CS_DARWIN_USER_TEMP_DIR
#ifndef MAXPATHLEN
#define MAXPATHLEN 1024
#endif
char path[MAXPATHLEN];
size_t len;
len = confstr(_CS_DARWIN_USER_TEMP_DIR, path, sizeof(path));
if (len > 0) {
tmpstr = path;
tmplen = len - 1;
if (len > sizeof(path)) tmpstr = 0;
}
# endif
tmpdir = rb_filesystem_str_new(tmpstr, tmplen);
# if defined _CS_DARWIN_USER_TEMP_DIR
if (!tmpstr) {
confstr(_CS_DARWIN_USER_TEMP_DIR, RSTRING_PTR(tmpdir), len);
}
# endif
#endif
#ifndef RB_PASS_KEYWORDS
/* untaint on Ruby < 2.7 */
FL_UNSET(tmpdir, FL_TAINT);
#endif
return tmpdir;
}
Returns system temporary directory; typically “/tmp”.
static VALUE
etc_uname(VALUE obj)
{
#ifdef _WIN32
OSVERSIONINFOW v;
SYSTEM_INFO s;
const char *sysname, *mach;
VALUE result, release, version;
VALUE vbuf, nodename = Qnil;
DWORD len = 0;
WCHAR *buf;
v.dwOSVersionInfoSize = sizeof(v);
if (!GetVersionExW(&v))
rb_sys_fail("GetVersionEx");
result = rb_hash_new();
switch (v.dwPlatformId) {
case VER_PLATFORM_WIN32s:
sysname = "Win32s";
break;
case VER_PLATFORM_WIN32_NT:
sysname = "Windows_NT";
break;
case VER_PLATFORM_WIN32_WINDOWS:
default:
sysname = "Windows";
break;
}
rb_hash_aset(result, ID2SYM(rb_intern("sysname")), rb_str_new_cstr(sysname));
release = rb_sprintf("%lu.%lu.%lu", v.dwMajorVersion, v.dwMinorVersion, v.dwBuildNumber);
rb_hash_aset(result, ID2SYM(rb_intern("release")), release);
version = rb_sprintf("%s Version %"PRIsVALUE": %"PRIsVALUE, sysname, release,
rb_w32_conv_from_wchar(v.szCSDVersion, rb_utf8_encoding()));
rb_hash_aset(result, ID2SYM(rb_intern("version")), version);
# if defined _MSC_VER && _MSC_VER < 1300
# define GET_COMPUTER_NAME(ptr, plen) GetComputerNameW(ptr, plen)
# else
# define GET_COMPUTER_NAME(ptr, plen) GetComputerNameExW(ComputerNameDnsFullyQualified, ptr, plen)
# endif
GET_COMPUTER_NAME(NULL, &len);
buf = ALLOCV_N(WCHAR, vbuf, len);
if (GET_COMPUTER_NAME(buf, &len)) {
nodename = rb_w32_conv_from_wchar(buf, rb_utf8_encoding());
}
ALLOCV_END(vbuf);
if (NIL_P(nodename)) nodename = rb_str_new(0, 0);
rb_hash_aset(result, ID2SYM(rb_intern("nodename")), nodename);
# ifndef PROCESSOR_ARCHITECTURE_AMD64
# define PROCESSOR_ARCHITECTURE_AMD64 9
# endif
# ifndef PROCESSOR_ARCHITECTURE_INTEL
# define PROCESSOR_ARCHITECTURE_INTEL 0
# endif
GetSystemInfo(&s);
switch (s.wProcessorArchitecture) {
case PROCESSOR_ARCHITECTURE_AMD64:
mach = "x64";
break;
case PROCESSOR_ARCHITECTURE_ARM:
mach = "ARM";
break;
case PROCESSOR_ARCHITECTURE_INTEL:
mach = "x86";
break;
default:
mach = "unknown";
break;
}
rb_hash_aset(result, ID2SYM(rb_intern("machine")), rb_str_new_cstr(mach));
#else
struct utsname u;
int ret;
VALUE result;
ret = uname(&u);
if (ret == -1)
rb_sys_fail("uname");
result = rb_hash_new();
rb_hash_aset(result, ID2SYM(rb_intern("sysname")), rb_str_new_cstr(u.sysname));
rb_hash_aset(result, ID2SYM(rb_intern("nodename")), rb_str_new_cstr(u.nodename));
rb_hash_aset(result, ID2SYM(rb_intern("release")), rb_str_new_cstr(u.release));
rb_hash_aset(result, ID2SYM(rb_intern("version")), rb_str_new_cstr(u.version));
rb_hash_aset(result, ID2SYM(rb_intern("machine")), rb_str_new_cstr(u.machine));
#endif
return result;
}
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"}