module Etc - Documentation for Ruby 4.0
Description: module Etc: tt> directory on Unix systems. tt>).
Keywords: ruby,module,Etc

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# 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

  The version

### Public Class Methods

confstr(name) → String
Source

    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"

endgrent
Source

    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.

endpwent
Source

    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.

getgrent → Etc::Group
Source

    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

getgrgid(group_id) → Etc::Group
Source

    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"]>

getgrnam(name) → Etc::Group
Source

    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"]>

getlogin → String
Source

    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'

getpwent → Etc::Passwd
Source

    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.

getpwnam(name) → Etc::Passwd
Source

    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">

getpwuid(uid) → Etc::Passwd
Source

    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">

group { |struct| block }
group → Etc::Group
Source

    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(', ')
    }

nprocessors → Integer
Source

    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

passwd { |struct| block }
passwd → Etc::Passwd
Source

    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
    }

setgrent
Source

    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.

setpwent
Source

    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.

sysconf(name) → Integer
Source

    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

sysconfdir → String
Source

    static VALUE
    etc_sysconfdir(VALUE obj)
    {
    #ifdef _WIN32
        return rb_w32_special_folder(CSIDL_COMMON_APPDATA);
    #elif defined(LOAD_RELATIVE)
        return rb_hash_aref(rbconfig(), rb_str_new_lit("sysconfdir"));
    #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.

systmpdir → String
Source

    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”.

uname → hash
Source

    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, SYMBOL_LIT("sysname"), rb_str_new_cstr(sysname));
        release = rb_sprintf("%lu.%lu.%lu", v.dwMajorVersion, v.dwMinorVersion, v.dwBuildNumber);
        rb_hash_aset(result, SYMBOL_LIT("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, SYMBOL_LIT("version"), version);

    #   define GET_COMPUTER_NAME(ptr, plen) GetComputerNameExW(ComputerNameDnsFullyQualified, ptr, plen)
        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, SYMBOL_LIT("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, SYMBOL_LIT("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, SYMBOL_LIT("sysname"), rb_str_new_cstr(u.sysname));
        rb_hash_aset(result, SYMBOL_LIT("nodename"), rb_str_new_cstr(u.nodename));
        rb_hash_aset(result, SYMBOL_LIT("release"), rb_str_new_cstr(u.release));
        rb_hash_aset(result, SYMBOL_LIT("version"), rb_str_new_cstr(u.version));
        rb_hash_aset(result, SYMBOL_LIT("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"}