module Etc
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.
Constants
- VERSION
Public Class Methods
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_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); }
Ends the process of scanning through the /etc/group
file begun by ::getgrent
, and closes the file.
static VALUE etc_endgrent(VALUE obj) { #ifdef HAVE_GETGRENT endgrent(); #endif return Qnil; }
Ends the process of scanning through the /etc/passwd
file begun with ::getpwent
, and closes the file.
static VALUE etc_endpwent(VALUE obj) { #ifdef HAVE_GETPWENT endpwent(); #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_getgrent(VALUE obj) { #ifdef HAVE_GETGRENT struct group *gr; if ((gr = getgrent()) != 0) { return setup_group(gr); } #endif return Qnil; }
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_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 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_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 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_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 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_getpwent(VALUE obj) { #ifdef HAVE_GETPWENT struct passwd *pw; if ((pw = getpwent()) != 0) { return setup_passwd(pw); } #endif return Qnil; }
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_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 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_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 }
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_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; }
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_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); }
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_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; }
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_setgrent(VALUE obj) { #ifdef HAVE_GETGRENT setgrent(); #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_setpwent(VALUE obj) { #ifdef HAVE_GETPWENT setpwent(); #endif return Qnil; }
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_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 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_sysconfdir(VALUE obj) { #ifdef _WIN32 return rb_w32_special_folder(CSIDL_COMMON_APPDATA); #else return rb_filesystem_str_new_cstr(SYSCONFDIR); #endif }
Returns system temporary directory; typically “/tmp”.
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 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"}
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; }