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A File is an abstraction of any file object accessible by the
program and is closely associated with class IO
File includes the methods of module FileTest as
class methods, allowing you to write (for example)
File.exist?("foo").
In the description of File methods, permission bits are a platform-specific set of bits that indicate permissions of a file. On Unix-based systems, permissions are viewed as a set of three octets, for the owner, the group, and the rest of the world. For each of these entities, permissions may be set to read, write, or execute the file:
The permission bits 0644 (in octal) would thus be interpreted
as read/write for owner, and read-only for group and other. Higher-order
bits may also be used to indicate the type of file (plain, directory, pipe,
socket, and so on) and various other special features. If the permissions
are for a directory, the meaning of the execute bit changes; when set the
directory can be searched.
On non-Posix operating systems, there may be only the ability to make a
file read-only or read-write. In this case, the remaining permission bits
will be synthesized to resemble typical values. For instance, on Windows NT
the default permission bits are 0644, which means read/write
for owner, read-only for all others. The only change that can be made is to
make the file read-only, which is reported as 0444.
Converts a pathname to an absolute pathname. Relative paths are referenced
from the current working directory of the process unless
dir_string is given, in which case it will be used as the starting
point. If the given pathname starts with a “~'' it is
NOT expanded, it is treated as a normal directory name.
File.absolute_path("~oracle/bin") #=> "<relative_path>/~oracle/bin"
 
               VALUE
rb_file_s_absolute_path(int argc, VALUE *argv)
{
    VALUE fname, dname;
    if (argc == 1) {
        return rb_file_absolute_path(argv[0], Qnil);
    }
    rb_scan_args(argc, argv, "11", &fname, &dname);
    return rb_file_absolute_path(fname, dname);
}
             
            Returns the last access time for the named file as a Time object).
File.atime("testfile") #=> Wed Apr 09 08:51:48 CDT 2003
 
               static VALUE
rb_file_s_atime(VALUE klass, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) {
        FilePathValue(fname);
        rb_sys_fail(RSTRING_PTR(fname));
    }
    return stat_atime(&st);
}
             
            Returns the last component of the filename given in file_name,
which must be formed using forward slashes (“/'')
regardless of the separator used on the local file system. If
suffix is given and present at the end of file_name, it
is removed.
File.basename("/home/gumby/work/ruby.rb") #=> "ruby.rb" File.basename("/home/gumby/work/ruby.rb", ".rb") #=> "ruby"
 
               static VALUE
rb_file_s_basename(int argc, VALUE *argv)
{
    VALUE fname, fext, basename;
    const char *name, *p;
    long f, n;
    if (rb_scan_args(argc, argv, "11", &fname, &fext) == 2) {
        rb_encoding *enc;
        StringValue(fext);
        if (!rb_enc_asciicompat(enc = rb_enc_get(fext))) {
            rb_raise(rb_eEncCompatError, "ascii incompatible character encodings: %s",
                     rb_enc_name(enc));
        }
    }
    FilePathStringValue(fname);
    if (!NIL_P(fext)) rb_enc_check(fname, fext);
    if (RSTRING_LEN(fname) == 0 || !*(name = RSTRING_PTR(fname)))
        return rb_str_new_shared(fname);
    p = ruby_find_basename(name, &f, &n);
    if (n >= 0) {
        if (NIL_P(fext) || !(f = rmext(p, n, StringValueCStr(fext)))) {
            f = n;
        }
        if (f == RSTRING_LEN(fname)) return rb_str_new_shared(fname);
    }
    basename = rb_str_new(p, f);
    rb_enc_copy(basename, fname);
    OBJ_INFECT(basename, fname);
    return basename;
}
             
            Returns true if the named file is a block device.
 
               static VALUE
rb_file_blockdev_p(VALUE obj, VALUE fname)
{
#ifndef S_ISBLK
#   ifdef S_IFBLK
#       define S_ISBLK(m) ((m & S_IFMT) == S_IFBLK)
#   else
#       define S_ISBLK(m) (0)  /* anytime false */
#   endif
#endif
#ifdef S_ISBLK
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (S_ISBLK(st.st_mode)) return Qtrue;
#endif
    return Qfalse;
}
             
            Returns true if the named file is a character device.
 
               static VALUE
rb_file_chardev_p(VALUE obj, VALUE fname)
{
#ifndef S_ISCHR
#   define S_ISCHR(m) ((m & S_IFMT) == S_IFCHR)
#endif
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (S_ISCHR(st.st_mode)) return Qtrue;
    return Qfalse;
}
             
            Changes permission bits on the named file(s) to the bit pattern represented
by mode_int. Actual effects are operating system dependent (see
the beginning of this section). On Unix systems, see chmod(2)
for details. Returns the number of files processed.
File.chmod(0644, "testfile", "out") #=> 2
 
               static VALUE
rb_file_s_chmod(int argc, VALUE *argv)
{
    VALUE vmode;
    VALUE rest;
    int mode;
    long n;
    rb_secure(2);
    rb_scan_args(argc, argv, "1*", &vmode, &rest);
    mode = NUM2INT(vmode);
    n = apply2files(chmod_internal, rest, &mode);
    return LONG2FIX(n);
}
             
            Changes the owner and group of the named file(s) to the given numeric owner
and group id's. Only a process with superuser privileges may change the
owner of a file. The current owner of a file may change the file's
group to any group to which the owner belongs. A nil or -1
owner or group id is ignored. Returns the number of files processed.
File.chown(nil, 100, "testfile")
 
               static VALUE
rb_file_s_chown(int argc, VALUE *argv)
{
    VALUE o, g, rest;
    struct chown_args arg;
    long n;
    rb_secure(2);
    rb_scan_args(argc, argv, "2*", &o, &g, &rest);
    if (NIL_P(o)) {
        arg.owner = -1;
    }
    else {
        arg.owner = NUM2UIDT(o);
    }
    if (NIL_P(g)) {
        arg.group = -1;
    }
    else {
        arg.group = NUM2GIDT(g);
    }
    n = apply2files(chown_internal, rest, &arg);
    return LONG2FIX(n);
}
             
            Returns the change time for the named file (the time at which directory information about the file was changed, not the file itself).
File.ctime("testfile") #=> Wed Apr 09 08:53:13 CDT 2003
 
               static VALUE
rb_file_s_ctime(VALUE klass, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) {
        FilePathValue(fname);
        rb_sys_fail(RSTRING_PTR(fname));
    }
    return stat_ctime(&st);
}
             
            Deletes the named files, returning the number of names passed as arguments.
Raises an exception on any error. See also Dir::rmdir.
 
               static VALUE
rb_file_s_unlink(VALUE klass, VALUE args)
{
    long n;
    rb_secure(2);
    n = apply2files(unlink_internal, args, 0);
    return LONG2FIX(n);
}
             
            Returns true if the named file is a directory,
false otherwise.
File.directory?(".")
 
               VALUE
rb_file_directory_p(VALUE obj, VALUE fname)
{
#ifndef S_ISDIR
#   define S_ISDIR(m) ((m & S_IFMT) == S_IFDIR)
#endif
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (S_ISDIR(st.st_mode)) return Qtrue;
    return Qfalse;
}
             
            Returns all components of the filename given in file_name except
the last one. The filename must be formed using forward slashes
(“/'') regardless of the separator used on the local
file system.
File.dirname("/home/gumby/work/ruby.rb") #=> "/home/gumby/work"
 
               static VALUE
rb_file_s_dirname(VALUE klass, VALUE fname)
{
    const char *name, *root, *p;
    VALUE dirname;
    FilePathStringValue(fname);
    name = StringValueCStr(fname);
    root = skiproot(name);
#ifdef DOSISH_UNC
    if (root > name + 1 && isdirsep(*name))
        root = skipprefix(name = root - 2);
#else
    if (root > name + 1)
        name = root - 1;
#endif
    p = strrdirsep(root);
    if (!p) {
        p = root;
    }
    if (p == name)
        return rb_usascii_str_new2(".");
#ifdef DOSISH_DRIVE_LETTER
    if (has_drive_letter(name) && isdirsep(*(name + 2))) {
        const char *top = skiproot(name + 2);
        dirname = rb_str_new(name, 3);
        rb_str_cat(dirname, top, p - top);
    }
    else
#endif
    dirname = rb_str_new(name, p - name);
#ifdef DOSISH_DRIVE_LETTER
    if (has_drive_letter(name) && root == name + 2 && p - name == 2)
        rb_str_cat(dirname, ".", 1);
#endif
    rb_enc_copy(dirname, fname);
    OBJ_INFECT(dirname, fname);
    return dirname;
}
             
            Returns true if the named file is executable by the effective
user id of this process.
 
               static VALUE
rb_file_executable_p(VALUE obj, VALUE fname)
{
    rb_secure(2);
    FilePathValue(fname);
    if (eaccess(StringValueCStr(fname), X_OK) < 0) return Qfalse;
    return Qtrue;
}
             
            Returns true if the named file is executable by the real user
id of this process.
 
               static VALUE
rb_file_executable_real_p(VALUE obj, VALUE fname)
{
    rb_secure(2);
    FilePathValue(fname);
    if (access(StringValueCStr(fname), X_OK) < 0) return Qfalse;
    return Qtrue;
}
             
            Returns true if the named file is a directory,
false otherwise.
 
               static VALUE
rb_file_exist_p(VALUE obj, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    return Qtrue;
}
             
            Return true if the named file exists.
 
               static VALUE
rb_file_exist_p(VALUE obj, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    return Qtrue;
}
             
            Converts a pathname to an absolute pathname. Relative paths are referenced
from the current working directory of the process unless
dir_string is given, in which case it will be used as the starting
point. The given pathname may start with a “~'', which
expands to the process owner's home directory (the environment variable
HOME must be set correctly).
“~user'' expands to the named user's home
directory.
File.expand_path("~oracle/bin") #=> "/home/oracle/bin" File.expand_path("../../bin", "/tmp/x") #=> "/bin"
 
               VALUE
rb_file_s_expand_path(int argc, VALUE *argv)
{
    VALUE fname, dname;
    if (argc == 1) {
        return rb_file_expand_path(argv[0], Qnil);
    }
    rb_scan_args(argc, argv, "11", &fname, &dname);
    return rb_file_expand_path(fname, dname);
}
             
            Returns the extension (the portion of file name in path after the period).
File.extname("test.rb") #=> ".rb" File.extname("a/b/d/test.rb") #=> ".rb" File.extname("test") #=> "" File.extname(".profile") #=> ""
 
               static VALUE
rb_file_s_extname(VALUE klass, VALUE fname)
{
    const char *name, *e;
    long len;
    VALUE extname;
    FilePathStringValue(fname);
    name = StringValueCStr(fname);
    e = ruby_find_extname(name, &len);
    if (len <= 1)
        return rb_str_new(0, 0);
    extname = rb_str_new(e, len);       /* keep the dot, too! */
    rb_enc_copy(extname, fname);
    OBJ_INFECT(extname, fname);
    return extname;
}
             
            Returns true if the named file exists and is a regular file.
 
               static VALUE
rb_file_file_p(VALUE obj, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (S_ISREG(st.st_mode)) return Qtrue;
    return Qfalse;
}
             
            Returns true if path matches against pattern The pattern is not a regular expression; instead it follows rules similar to shell filename globbing. It may contain the following metacharacters:
*
Matches any file. Can be restricted by other values in the glob.
* will match all files; c* will match all files
beginning with c; *c will match all files ending
with c; and c will match all
files that have c in them (including at the beginning or end).
Equivalent to / .* /x in regexp.
**
Matches directories recursively or files expansively.
?
Matches any one character. Equivalent to /.{1}/ in regexp.
[set]
Matches any one character in set. Behaves exactly like
character sets in Regexp, including set negation
([^a-z]).
Escapes the next metacharacter.
flags is a bitwise OR of the FNM_xxx parameters. The
same glob pattern and flags are used by Dir::glob.
File.fnmatch('cat', 'cat') #=> true # match entire string File.fnmatch('cat', 'category') #=> false # only match partial string File.fnmatch('c{at,ub}s', 'cats') #=> false # { } isn't supported File.fnmatch('c?t', 'cat') #=> true # '?' match only 1 character File.fnmatch('c??t', 'cat') #=> false # ditto File.fnmatch('c*', 'cats') #=> true # '*' match 0 or more characters File.fnmatch('c*t', 'c/a/b/t') #=> true # ditto File.fnmatch('ca[a-z]', 'cat') #=> true # inclusive bracket expression File.fnmatch('ca[^t]', 'cat') #=> false # exclusive bracket expression ('^' or '!') File.fnmatch('cat', 'CAT') #=> false # case sensitive File.fnmatch('cat', 'CAT', File::FNM_CASEFOLD) #=> true # case insensitive File.fnmatch('?', '/', File::FNM_PATHNAME) #=> false # wildcard doesn't match '/' on FNM_PATHNAME File.fnmatch('*', '/', File::FNM_PATHNAME) #=> false # ditto File.fnmatch('[/]', '/', File::FNM_PATHNAME) #=> false # ditto File.fnmatch('\?', '?') #=> true # escaped wildcard becomes ordinary File.fnmatch('\a', 'a') #=> true # escaped ordinary remains ordinary File.fnmatch('\a', '\a', File::FNM_NOESCAPE) #=> true # FNM_NOESACPE makes '\' ordinary File.fnmatch('[\?]', '?') #=> true # can escape inside bracket expression File.fnmatch('*', '.profile') #=> false # wildcard doesn't match leading File.fnmatch('*', '.profile', File::FNM_DOTMATCH) #=> true # period by default. File.fnmatch('.*', '.profile') #=> true rbfiles = '**' '/' '*.rb' # you don't have to do like this. just write in single string. File.fnmatch(rbfiles, 'main.rb') #=> false File.fnmatch(rbfiles, './main.rb') #=> false File.fnmatch(rbfiles, 'lib/song.rb') #=> true File.fnmatch('**.rb', 'main.rb') #=> true File.fnmatch('**.rb', './main.rb') #=> false File.fnmatch('**.rb', 'lib/song.rb') #=> true File.fnmatch('*', 'dave/.profile') #=> true pattern = '*' '/' '*' File.fnmatch(pattern, 'dave/.profile', File::FNM_PATHNAME) #=> false File.fnmatch(pattern, 'dave/.profile', File::FNM_PATHNAME | File::FNM_DOTMATCH) #=> true pattern = '**' '/' 'foo' File.fnmatch(pattern, 'a/b/c/foo', File::FNM_PATHNAME) #=> true File.fnmatch(pattern, '/a/b/c/foo', File::FNM_PATHNAME) #=> true File.fnmatch(pattern, 'c:/a/b/c/foo', File::FNM_PATHNAME) #=> true File.fnmatch(pattern, 'a/.b/c/foo', File::FNM_PATHNAME) #=> false File.fnmatch(pattern, 'a/.b/c/foo', File::FNM_PATHNAME | File::FNM_DOTMATCH) #=> true
 
               static VALUE
file_s_fnmatch(int argc, VALUE *argv, VALUE obj)
{
    VALUE pattern, path;
    VALUE rflags;
    int flags;
    if (rb_scan_args(argc, argv, "21", &pattern, &path, &rflags) == 3)
        flags = NUM2INT(rflags);
    else
        flags = 0;
    StringValue(pattern);
    FilePathStringValue(path);
    if (fnmatch(RSTRING_PTR(pattern), rb_enc_get(pattern), RSTRING_PTR(path),
                flags) == 0)
        return Qtrue;
    return Qfalse;
}
             
            Returns true if path matches against pattern The pattern is not a regular expression; instead it follows rules similar to shell filename globbing. It may contain the following metacharacters:
*
Matches any file. Can be restricted by other values in the glob.
* will match all files; c* will match all files
beginning with c; *c will match all files ending
with c; and c will match all
files that have c in them (including at the beginning or end).
Equivalent to / .* /x in regexp.
**
Matches directories recursively or files expansively.
?
Matches any one character. Equivalent to /.{1}/ in regexp.
[set]
Matches any one character in set. Behaves exactly like
character sets in Regexp, including set negation
([^a-z]).
Escapes the next metacharacter.
flags is a bitwise OR of the FNM_xxx parameters. The
same glob pattern and flags are used by Dir::glob.
File.fnmatch('cat', 'cat') #=> true # match entire string File.fnmatch('cat', 'category') #=> false # only match partial string File.fnmatch('c{at,ub}s', 'cats') #=> false # { } isn't supported File.fnmatch('c?t', 'cat') #=> true # '?' match only 1 character File.fnmatch('c??t', 'cat') #=> false # ditto File.fnmatch('c*', 'cats') #=> true # '*' match 0 or more characters File.fnmatch('c*t', 'c/a/b/t') #=> true # ditto File.fnmatch('ca[a-z]', 'cat') #=> true # inclusive bracket expression File.fnmatch('ca[^t]', 'cat') #=> false # exclusive bracket expression ('^' or '!') File.fnmatch('cat', 'CAT') #=> false # case sensitive File.fnmatch('cat', 'CAT', File::FNM_CASEFOLD) #=> true # case insensitive File.fnmatch('?', '/', File::FNM_PATHNAME) #=> false # wildcard doesn't match '/' on FNM_PATHNAME File.fnmatch('*', '/', File::FNM_PATHNAME) #=> false # ditto File.fnmatch('[/]', '/', File::FNM_PATHNAME) #=> false # ditto File.fnmatch('\?', '?') #=> true # escaped wildcard becomes ordinary File.fnmatch('\a', 'a') #=> true # escaped ordinary remains ordinary File.fnmatch('\a', '\a', File::FNM_NOESCAPE) #=> true # FNM_NOESACPE makes '\' ordinary File.fnmatch('[\?]', '?') #=> true # can escape inside bracket expression File.fnmatch('*', '.profile') #=> false # wildcard doesn't match leading File.fnmatch('*', '.profile', File::FNM_DOTMATCH) #=> true # period by default. File.fnmatch('.*', '.profile') #=> true rbfiles = '**' '/' '*.rb' # you don't have to do like this. just write in single string. File.fnmatch(rbfiles, 'main.rb') #=> false File.fnmatch(rbfiles, './main.rb') #=> false File.fnmatch(rbfiles, 'lib/song.rb') #=> true File.fnmatch('**.rb', 'main.rb') #=> true File.fnmatch('**.rb', './main.rb') #=> false File.fnmatch('**.rb', 'lib/song.rb') #=> true File.fnmatch('*', 'dave/.profile') #=> true pattern = '*' '/' '*' File.fnmatch(pattern, 'dave/.profile', File::FNM_PATHNAME) #=> false File.fnmatch(pattern, 'dave/.profile', File::FNM_PATHNAME | File::FNM_DOTMATCH) #=> true pattern = '**' '/' 'foo' File.fnmatch(pattern, 'a/b/c/foo', File::FNM_PATHNAME) #=> true File.fnmatch(pattern, '/a/b/c/foo', File::FNM_PATHNAME) #=> true File.fnmatch(pattern, 'c:/a/b/c/foo', File::FNM_PATHNAME) #=> true File.fnmatch(pattern, 'a/.b/c/foo', File::FNM_PATHNAME) #=> false File.fnmatch(pattern, 'a/.b/c/foo', File::FNM_PATHNAME | File::FNM_DOTMATCH) #=> true
 
               static VALUE
file_s_fnmatch(int argc, VALUE *argv, VALUE obj)
{
    VALUE pattern, path;
    VALUE rflags;
    int flags;
    if (rb_scan_args(argc, argv, "21", &pattern, &path, &rflags) == 3)
        flags = NUM2INT(rflags);
    else
        flags = 0;
    StringValue(pattern);
    FilePathStringValue(path);
    if (fnmatch(RSTRING_PTR(pattern), rb_enc_get(pattern), RSTRING_PTR(path),
                flags) == 0)
        return Qtrue;
    return Qfalse;
}
             
            Identifies the type of the named file; the return string is one of
“file'', “directory'',
“characterSpecial'',
“blockSpecial'', “fifo'',
“link'', “socket'', or
“unknown''.
File.ftype("testfile") #=> "file" File.ftype("/dev/tty") #=> "characterSpecial" File.ftype("/tmp/.X11-unix/X0") #=> "socket"
 
               static VALUE
rb_file_s_ftype(VALUE klass, VALUE fname)
{
    struct stat st;
    rb_secure(2);
    FilePathValue(fname);
    if (lstat(StringValueCStr(fname), &st) == -1) {
        rb_sys_fail(RSTRING_PTR(fname));
    }
    return rb_file_ftype(&st);
}
             
            Returns true if the named file exists and the effective group
id of the calling process is the owner of the file. Returns
false on Windows.
 
               static VALUE
rb_file_grpowned_p(VALUE obj, VALUE fname)
{
#ifndef _WIN32
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (group_member(st.st_gid)) return Qtrue;
#endif
    return Qfalse;
}
             
            Returns true if the named files are identical.
open("a", "w") {} p File.identical?("a", "a") #=> true p File.identical?("a", "./a") #=> true File.link("a", "b") p File.identical?("a", "b") #=> true File.symlink("a", "c") p File.identical?("a", "c") #=> true open("d", "w") {} p File.identical?("a", "d") #=> false
 
               static VALUE
rb_file_identical_p(VALUE obj, VALUE fname1, VALUE fname2)
{
#ifndef DOSISH
    struct stat st1, st2;
    if (rb_stat(fname1, &st1) < 0) return Qfalse;
    if (rb_stat(fname2, &st2) < 0) return Qfalse;
    if (st1.st_dev != st2.st_dev) return Qfalse;
    if (st1.st_ino != st2.st_ino) return Qfalse;
#else
#ifdef _WIN32
    BY_HANDLE_FILE_INFORMATION st1, st2;
    HANDLE f1 = 0, f2 = 0;
#endif
    rb_secure(2);
#ifdef _WIN32
    f1 = w32_io_info(&fname1, &st1);
    if (f1 == INVALID_HANDLE_VALUE) return Qfalse;
    f2 = w32_io_info(&fname2, &st2);
    if (f1) CloseHandle(f1);
    if (f2 == INVALID_HANDLE_VALUE) return Qfalse;
    if (f2) CloseHandle(f2);
    if (st1.dwVolumeSerialNumber == st2.dwVolumeSerialNumber &&
        st1.nFileIndexHigh == st2.nFileIndexHigh &&
        st1.nFileIndexLow == st2.nFileIndexLow)
        return Qtrue;
    if (!f1 || !f2) return Qfalse;
    if (rb_w32_iswin95()) return Qfalse;
#else
    FilePathValue(fname1);
    fname1 = rb_str_new4(fname1);
    FilePathValue(fname2);
    if (access(RSTRING_PTR(fname1), 0)) return Qfalse;
    if (access(RSTRING_PTR(fname2), 0)) return Qfalse;
#endif
    fname1 = rb_file_expand_path(fname1, Qnil);
    fname2 = rb_file_expand_path(fname2, Qnil);
    if (RSTRING_LEN(fname1) != RSTRING_LEN(fname2)) return Qfalse;
    if (rb_memcicmp(RSTRING_PTR(fname1), RSTRING_PTR(fname2), RSTRING_LEN(fname1)))
        return Qfalse;
#endif
    return Qtrue;
}
             
            Returns a new string formed by joining the strings using
File::SEPARATOR.
File.join("usr", "mail", "gumby") #=> "usr/mail/gumby"
 
               static VALUE
rb_file_s_join(VALUE klass, VALUE args)
{
    return rb_file_join(args, separator);
}
             
            Equivalent to File::chmod, but does not follow symbolic links
(so it will change the permissions associated with the link, not the file
referenced by the link). Often not available.
 
               static VALUE
rb_file_s_lchmod(int argc, VALUE *argv)
{
    VALUE vmode;
    VALUE rest;
    long mode, n;
    rb_secure(2);
    rb_scan_args(argc, argv, "1*", &vmode, &rest);
    mode = NUM2INT(vmode);
    n = apply2files(lchmod_internal, rest, (void *)(long)mode);
    return LONG2FIX(n);
}
             
            Equivalent to File::chown, but does not follow symbolic links
(so it will change the owner associated with the link, not the file
referenced by the link). Often not available. Returns number of files in
the argument list.
 
               static VALUE
rb_file_s_lchown(int argc, VALUE *argv)
{
    VALUE o, g, rest;
    struct chown_args arg;
    long n;
    rb_secure(2);
    rb_scan_args(argc, argv, "2*", &o, &g, &rest);
    if (NIL_P(o)) {
        arg.owner = -1;
    }
    else {
        arg.owner = NUM2UIDT(o);
    }
    if (NIL_P(g)) {
        arg.group = -1;
    }
    else {
        arg.group = NUM2GIDT(g);
    }
    n = apply2files(lchown_internal, rest, &arg);
    return LONG2FIX(n);
}
             
            Creates a new name for an existing file using a hard link. Will not
overwrite new_name if it already exists (raising a subclass of
SystemCallError). Not available on all platforms.
File.link("testfile", ".testfile") #=> 0 IO.readlines(".testfile")[0] #=> "This is line one\n"
 
               static VALUE
rb_file_s_link(VALUE klass, VALUE from, VALUE to)
{
#ifdef HAVE_LINK
    rb_secure(2);
    FilePathValue(from);
    FilePathValue(to);
    if (link(StringValueCStr(from), StringValueCStr(to)) < 0) {
        sys_fail2(from, to);
    }
    return INT2FIX(0);
#else
    rb_notimplement();
    return Qnil;                /* not reached */
#endif
}
             
            Same as File::stat, but does not follow the last symbolic
link. Instead, reports on the link itself.
File.symlink("testfile", "link2test") #=> 0 File.stat("testfile").size #=> 66 File.lstat("link2test").size #=> 8 File.stat("link2test").size #=> 66
 
               static VALUE
rb_file_s_lstat(VALUE klass, VALUE fname)
{
#ifdef HAVE_LSTAT
    struct stat st;
    rb_secure(2);
    FilePathValue(fname);
    if (lstat(StringValueCStr(fname), &st) == -1) {
        rb_sys_fail(RSTRING_PTR(fname));
    }
    return stat_new(&st);
#else
    return rb_file_s_stat(klass, fname);
#endif
}
             
            Returns the modification time for the named file as a Time object.
File.mtime("testfile") #=> Tue Apr 08 12:58:04 CDT 2003
 
               static VALUE
rb_file_s_mtime(VALUE klass, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) {
        FilePathValue(fname);
        rb_sys_fail(RSTRING_PTR(fname));
    }
    return stat_mtime(&st);
}
             
            Opens the file named by filename according to mode
(default is “r'') and returns a new File object.
See the description of class IO for a description of
mode.  The file mode may optionally be specified as a
Fixnum  by or-ing together the flags (O_RDONLY etc, 
again described under IO).
Optional permission bits may be given in perm.  These mode and
permission bits are platform dependent;  on Unix systems, see
open(2) for details.
Optional opt parameter is same as in <code.IO.open</code>.
f = File.new("testfile", "r") f = File.new("newfile", "w+") f = File.new("newfile", File::CREAT|File::TRUNC|File::RDWR, 0644)
 
               static VALUE
rb_file_initialize(int argc, VALUE *argv, VALUE io)
{
    if (RFILE(io)->fptr) {
        rb_raise(rb_eRuntimeError, "reinitializing File");
    }
    if (0 < argc && argc < 3) {
        VALUE fd = rb_check_convert_type(argv[0], T_FIXNUM, "Fixnum", "to_int");
        if (!NIL_P(fd)) {
            argv[0] = fd;
            return rb_io_initialize(argc, argv, io);
        }
    }
    rb_open_file(argc, argv, io);
    return io;
}
             
            With no associated block, open is a synonym for
File.new. If the optional code block is given, it will be
passed file as an argument, and the File
object will automatically be closed when the block terminates. In this
instance, File.open returns the value of the block.
 
               static VALUE
rb_io_s_open(int argc, VALUE *argv, VALUE klass)
{
    VALUE io = rb_class_new_instance(argc, argv, klass);
    if (rb_block_given_p()) {
        return rb_ensure(rb_yield, io, io_close, io);
    }
    return io;
}
             
            Returns true if the named file exists and the effective used
id of the calling process is the owner of the file.
 
               static VALUE
rb_file_owned_p(VALUE obj, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (st.st_uid == geteuid()) return Qtrue;
    return Qfalse;
}
             
            Returns the string representation of the path
File.path("/dev/null") #=> "/dev/null" File.path(Pathname.new("/tmp")) #=> "/tmp"
 
               static VALUE
rb_file_s_path(VALUE klass, VALUE fname)
{
    return rb_get_path(fname);
}
             
            Returns true if the named file is a pipe.
 
               static VALUE
rb_file_pipe_p(VALUE obj, VALUE fname)
{
#ifdef S_IFIFO
#  ifndef S_ISFIFO
#    define S_ISFIFO(m) ((m & S_IFMT) == S_IFIFO)
#  endif
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (S_ISFIFO(st.st_mode)) return Qtrue;
#endif
    return Qfalse;
}
             
            Returns true if the named file is readable by the effective
user id of this process.
 
               static VALUE
rb_file_readable_p(VALUE obj, VALUE fname)
{
    rb_secure(2);
    FilePathValue(fname);
    if (eaccess(StringValueCStr(fname), R_OK) < 0) return Qfalse;
    return Qtrue;
}
             
            Returns true if the named file is readable by the real user id
of this process.
 
               static VALUE
rb_file_readable_real_p(VALUE obj, VALUE fname)
{
    rb_secure(2);
    FilePathValue(fname);
    if (access(StringValueCStr(fname), R_OK) < 0) return Qfalse;
    return Qtrue;
}
             
            Returns the name of the file referenced by the given link. Not available on all platforms.
File.symlink("testfile", "link2test") #=> 0 File.readlink("link2test") #=> "testfile"
 
               static VALUE
rb_file_s_readlink(VALUE klass, VALUE path)
{
#ifdef HAVE_READLINK
    char *buf;
    int size = 100;
    int rv;
    VALUE v;
    rb_secure(2);
    FilePathValue(path);
    buf = xmalloc(size);
    while ((rv = readlink(RSTRING_PTR(path), buf, size)) == size
#ifdef _AIX
            || (rv < 0 && errno == ERANGE) /* quirky behavior of GPFS */
#endif
        ) {
        size *= 2;
        buf = xrealloc(buf, size);
    }
    if (rv < 0) {
        xfree(buf);
        rb_sys_fail_path(path);
    }
    v = rb_tainted_str_new(buf, rv);
    xfree(buf);
    return v;
#else
    rb_notimplement();
    return Qnil;                /* not reached */
#endif
}
             
            Renames the given file to the new name. Raises a
SystemCallError if the file cannot be renamed.
File.rename("afile", "afile.bak") #=> 0
 
               static VALUE
rb_file_s_rename(VALUE klass, VALUE from, VALUE to)
{
    const char *src, *dst;
    rb_secure(2);
    FilePathValue(from);
    FilePathValue(to);
    src = StringValueCStr(from);
    dst = StringValueCStr(to);
#if defined __CYGWIN__
    errno = 0;
#endif
    if (rename(src, dst) < 0) {
#if defined DOSISH && !defined _WIN32
        switch (errno) {
          case EEXIST:
#if defined (__EMX__)
          case EACCES:
#endif
            if (chmod(dst, 0666) == 0 &&
                unlink(dst) == 0 &&
                rename(src, dst) == 0)
                return INT2FIX(0);
        }
#endif
        sys_fail2(from, to);
    }
    return INT2FIX(0);
}
             
            Returns true if the named file has the setgid bit set.
 
               static VALUE
rb_file_sgid_p(VALUE obj, VALUE fname)
{
#ifdef S_ISGID
    return check3rdbyte(fname, S_ISGID);
#else
    return Qfalse;
#endif
}
             
            Returns true if the named file has the setuid bit set.
 
               static VALUE
rb_file_suid_p(VALUE obj, VALUE fname)
{
#ifdef S_ISUID
    return check3rdbyte(fname, S_ISUID);
#else
    return Qfalse;
#endif
}
             
            Returns the size of file_name.
 
               static VALUE
rb_file_s_size(VALUE klass, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) {
        FilePathValue(fname);
        rb_sys_fail(RSTRING_PTR(fname));
    }
    return OFFT2NUM(st.st_size);
}
             
            Returns nil if file_name doesn't exist or has
zero size, the size of the file otherwise.
 
               static VALUE
rb_file_size_p(VALUE obj, VALUE fname)
{
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qnil;
    if (st.st_size == 0) return Qnil;
    return OFFT2NUM(st.st_size);
}
             
            Returns true if the named file is a socket.
 
               static VALUE
rb_file_socket_p(VALUE obj, VALUE fname)
{
#ifndef S_ISSOCK
#  ifdef _S_ISSOCK
#    define S_ISSOCK(m) _S_ISSOCK(m)
#  else
#    ifdef _S_IFSOCK
#      define S_ISSOCK(m) ((m & S_IFMT) == _S_IFSOCK)
#    else
#      ifdef S_IFSOCK
#        define S_ISSOCK(m) ((m & S_IFMT) == S_IFSOCK)
#      endif
#    endif
#  endif
#endif
#ifdef S_ISSOCK
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qfalse;
    if (S_ISSOCK(st.st_mode)) return Qtrue;
#endif
    return Qfalse;
}
             
            Splits the given string into a directory and a file component and returns
them in a two-element array. See also File::dirname and
File::basename.
File.split("/home/gumby/.profile") #=> ["/home/gumby", ".profile"]
 
               static VALUE
rb_file_s_split(VALUE klass, VALUE path)
{
    FilePathStringValue(path);          /* get rid of converting twice */
    return rb_assoc_new(rb_file_s_dirname(Qnil, path), rb_file_s_basename(1,&path));
}
             
            Returns a File::Stat object for the named file (see
File::Stat).
File.stat("testfile").mtime #=> Tue Apr 08 12:58:04 CDT 2003
 
               static VALUE
rb_file_s_stat(VALUE klass, VALUE fname)
{
    struct stat st;
    rb_secure(4);
    FilePathValue(fname);
    if (rb_stat(fname, &st) < 0) {
        FilePathValue(fname);
        rb_sys_fail(RSTRING_PTR(fname));
    }
    return stat_new(&st);
}
             
            Returns true if the named file has the sticky bit set.
 
               static VALUE
rb_file_sticky_p(VALUE obj, VALUE fname)
{
#ifdef S_ISVTX
    return check3rdbyte(fname, S_ISVTX);
#else
    return Qnil;
#endif
}
             
            Creates a symbolic link called new_name for the existing file
old_name. Raises a NotImplemented exception on
platforms that do not support symbolic links.
File.symlink("testfile", "link2test") #=> 0
 
               static VALUE
rb_file_s_symlink(VALUE klass, VALUE from, VALUE to)
{
#ifdef HAVE_SYMLINK
    rb_secure(2);
    FilePathValue(from);
    FilePathValue(to);
    if (symlink(StringValueCStr(from), StringValueCStr(to)) < 0) {
        sys_fail2(from, to);
    }
    return INT2FIX(0);
#else
    rb_notimplement();
    return Qnil;                /* not reached */
#endif
}
             
            Returns true if the named file is a symbolic link.
 
               static VALUE
rb_file_symlink_p(VALUE obj, VALUE fname)
{
#ifndef S_ISLNK
#  ifdef _S_ISLNK
#    define S_ISLNK(m) _S_ISLNK(m)
#  else
#    ifdef _S_IFLNK
#      define S_ISLNK(m) ((m & S_IFMT) == _S_IFLNK)
#    else
#      ifdef S_IFLNK
#        define S_ISLNK(m) ((m & S_IFMT) == S_IFLNK)
#      endif
#    endif
#  endif
#endif
#ifdef S_ISLNK
    struct stat st;
    rb_secure(2);
    FilePathValue(fname);
    if (lstat(StringValueCStr(fname), &st) < 0) return Qfalse;
    if (S_ISLNK(st.st_mode)) return Qtrue;
#endif
    return Qfalse;
}
             
            Truncates the file file_name to be at most integer bytes long. Not available on all platforms.
f = File.new("out", "w") f.write("1234567890") #=> 10 f.close #=> nil File.truncate("out", 5) #=> 0 File.size("out") #=> 5
 
               static VALUE
rb_file_s_truncate(VALUE klass, VALUE path, VALUE len)
{
    off_t pos;
    rb_secure(2);
    pos = NUM2OFFT(len);
    FilePathValue(path);
#ifdef HAVE_TRUNCATE
    if (truncate(StringValueCStr(path), pos) < 0)
        rb_sys_fail(RSTRING_PTR(path));
#else
# ifdef HAVE_CHSIZE
    {
        int tmpfd;
#  ifdef _WIN32
        if ((tmpfd = open(StringValueCStr(path), O_RDWR)) < 0) {
            rb_sys_fail(RSTRING_PTR(path));
        }
#  else
        if ((tmpfd = open(StringValueCStr(path), 0)) < 0) {
            rb_sys_fail(RSTRING_PTR(path));
        }
#  endif
        if (chsize(tmpfd, pos) < 0) {
            close(tmpfd);
            rb_sys_fail(RSTRING_PTR(path));
        }
        close(tmpfd);
    }
# else
    rb_notimplement();
# endif
#endif
    return INT2FIX(0);
}
             
            Returns the current umask value for this process. If the optional argument
is given, set the umask to that value and return the previous value. Umask
values are subtracted from the default permissions, so a umask of
0222 would make a file read-only for everyone.
File.umask(0006) #=> 18 File.umask #=> 6
 
               static VALUE
rb_file_s_umask(int argc, VALUE *argv)
{
    int omask = 0;
    rb_secure(2);
    if (argc == 0) {
        omask = umask(0);
        umask(omask);
    }
    else if (argc == 1) {
        omask = umask(NUM2INT(argv[0]));
    }
    else {
        rb_raise(rb_eArgError, "wrong number of arguments");
    }
    return INT2FIX(omask);
}
             
            Deletes the named files, returning the number of names passed as arguments.
Raises an exception on any error. See also Dir::rmdir.
 
               static VALUE
rb_file_s_unlink(VALUE klass, VALUE args)
{
    long n;
    rb_secure(2);
    n = apply2files(unlink_internal, args, 0);
    return LONG2FIX(n);
}
             
            Sets the access and modification times of each named file to the first two arguments. Returns the number of file names in the argument list.
 
               static VALUE
rb_file_s_utime(int argc, VALUE *argv)
{
    VALUE atime, mtime, rest;
    struct timespec tss[2], *tsp = NULL;
    long n;
    rb_secure(2);
    rb_scan_args(argc, argv, "2*", &atime, &mtime, &rest);
    if (!NIL_P(atime) || !NIL_P(mtime)) {
        tsp = tss;
        tsp[0] = rb_time_timespec(atime);
        tsp[1] = rb_time_timespec(mtime);
    }
    n = apply2files(utime_internal, rest, tsp);
    return LONG2FIX(n);
}
             
            If file_name is readable by others, returns an integer
representing the file permission bits of file_name. Returns
nil otherwise. The meaning of the bits is platform dependent;
on Unix systems, see stat(2).
File.world_readable?("/etc/passwd") # => 420 m = File.world_readable?("/etc/passwd") sprintf("%o", m) # => "644"
 
               static VALUE
rb_file_world_readable_p(VALUE obj, VALUE fname)
{
#ifdef S_IROTH
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qnil;
    if ((st.st_mode & (S_IROTH)) == S_IROTH) {
        return UINT2NUM(st.st_mode & (S_IRUGO|S_IWUGO|S_IXUGO));
    }
#endif
    return Qnil;
}
             
            If file_name is writable by others, returns an integer
representing the file permission bits of file_name. Returns
nil otherwise. The meaning of the bits is platform dependent;
on Unix systems, see stat(2).
File.world_writable?("/tmp") #=> 511 m = File.world_writable?("/tmp") sprintf("%o", m) #=> "777"
 
               static VALUE
rb_file_world_writable_p(VALUE obj, VALUE fname)
{
#ifdef S_IWOTH
    struct stat st;
    if (rb_stat(fname, &st) < 0) return Qnil;
    if ((st.st_mode & (S_IWOTH)) == S_IWOTH) {
        return UINT2NUM(st.st_mode & (S_IRUGO|S_IWUGO|S_IXUGO));
    }
#endif
    return Qnil;
}
             
            Returns true if the named file is writable by the effective
user id of this process.
 
               static VALUE
rb_file_writable_p(VALUE obj, VALUE fname)
{
    rb_secure(2);
    FilePathValue(fname);
    if (eaccess(StringValueCStr(fname), W_OK) < 0) return Qfalse;
    return Qtrue;
}
             
            Returns true if the named file is writable by the real user id
of this process.
 
               static VALUE
rb_file_writable_real_p(VALUE obj, VALUE fname)
{
    rb_secure(2);
    FilePathValue(fname);
    if (access(StringValueCStr(fname), W_OK) < 0) return Qfalse;
    return Qtrue;
}
             
            Returns the last access time (a Time object)
for <i>file</i>, or epoch if <i>file</i> has not been accessed.
  File.new("testfile").atime   #=> Wed Dec 31 18:00:00 CST 1969
            
            
             
               static VALUE
rb_file_atime(VALUE obj)
{
    rb_io_t *fptr;
    struct stat st;
    GetOpenFile(obj, fptr);
    if (fstat(fptr->fd, &st) == -1) {
        rb_sys_fail_path(fptr->pathv);
    }
    return stat_atime(&st);
}
             
            Changes permission bits on file to the bit pattern represented by
mode_int. Actual effects are platform dependent; on Unix systems,
see chmod(2) for details. Follows symbolic links. Also see
File#lchmod.
f = File.new("out", "w"); f.chmod(0644) #=> 0
 
               static VALUE
rb_file_chmod(VALUE obj, VALUE vmode)
{
    rb_io_t *fptr;
    int mode;
    rb_secure(2);
    mode = NUM2INT(vmode);
    GetOpenFile(obj, fptr);
#ifdef HAVE_FCHMOD
    if (fchmod(fptr->fd, mode) == -1)
        rb_sys_fail_path(fptr->pathv);
#else
    if (NIL_P(fptr->pathv)) return Qnil;
    if (chmod(RSTRING_PTR(fptr->pathv), mode) == -1)
        rb_sys_fail_path(fptr->pathv);
#endif
    return INT2FIX(0);
}
             
            Changes the owner and group of file to the given numeric owner and
group id's. Only a process with superuser privileges may change the
owner of a file. The current owner of a file may change the file's
group to any group to which the owner belongs. A nil or -1
owner or group id is ignored. Follows symbolic links. See also
File#lchown.
File.new("testfile").chown(502, 1000)
 
               static VALUE
rb_file_chown(VALUE obj, VALUE owner, VALUE group)
{
    rb_io_t *fptr;
    int o, g;
    rb_secure(2);
    o = NIL_P(owner) ? -1 : NUM2INT(owner);
    g = NIL_P(group) ? -1 : NUM2INT(group);
    GetOpenFile(obj, fptr);
#if defined(__CYGWIN32__) || defined(_WIN32) || defined(__EMX__)
    if (NIL_P(fptr->pathv)) return Qnil;
    if (chown(RSTRING_PTR(fptr->pathv), o, g) == -1)
        rb_sys_fail_path(fptr->pathv);
#else
    if (fchown(fptr->fd, o, g) == -1)
        rb_sys_fail_path(fptr->pathv);
#endif
    return INT2FIX(0);
}
             
            Returns the change time for file (that is, the time directory information about the file was changed, not the file itself).
File.new("testfile").ctime #=> Wed Apr 09 08:53:14 CDT 2003
 
               static VALUE
rb_file_ctime(VALUE obj)
{
    rb_io_t *fptr;
    struct stat st;
    GetOpenFile(obj, fptr);
    if (fstat(fptr->fd, &st) == -1) {
        rb_sys_fail_path(fptr->pathv);
    }
    return stat_ctime(&st);
}
             
            Locks or unlocks a file according to locking_constant (a logical
or of the values in the table below). Returns false
if File::LOCK_NB is specified and the operation would
otherwise have blocked. Not available on all platforms.
Locking constants (in class File):
LOCK_EX   | Exclusive lock. Only one process may hold an
          | exclusive lock for a given file at a time.
----------+------------------------------------------------
LOCK_NB   | Don't block when locking. May be combined
          | with other lock options using logical or.
----------+------------------------------------------------
LOCK_SH   | Shared lock. Multiple processes may each hold a
          | shared lock for a given file at the same time.
----------+------------------------------------------------
LOCK_UN   | Unlock.
Example:
File.new("testfile").flock(File::LOCK_UN) #=> 0
 
               static VALUE
rb_file_flock(VALUE obj, VALUE operation)
{
#ifndef __CHECKER__
    rb_io_t *fptr;
    int op[2], op1;
    rb_secure(2);
    op[1] = op1 = NUM2INT(operation);
    GetOpenFile(obj, fptr);
    op[0] = fptr->fd;
    if (fptr->mode & FMODE_WRITABLE) {
        rb_io_flush(obj);
    }
    while ((int)rb_thread_blocking_region(rb_thread_flock, op, RUBY_UBF_IO, 0) < 0) {
        switch (errno) {
          case EAGAIN:
          case EACCES:
#if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN
          case EWOULDBLOCK:
#endif
            if (op1 & LOCK_NB) return Qfalse;
            rb_thread_polling();
            rb_io_check_closed(fptr);
            continue;
          case EINTR:
#if defined(ERESTART)
          case ERESTART:
#endif
            break;
          default:
            rb_sys_fail_path(fptr->pathv);
        }
    }
#endif
    return INT2FIX(0);
}
             
            Same as IO#stat, but does not follow the last symbolic link.
Instead, reports on the link itself.
File.symlink("testfile", "link2test") #=> 0 File.stat("testfile").size #=> 66 f = File.new("link2test") f.lstat.size #=> 8 f.stat.size #=> 66
 
               static VALUE
rb_file_lstat(VALUE obj)
{
#ifdef HAVE_LSTAT
    rb_io_t *fptr;
    struct stat st;
    rb_secure(2);
    GetOpenFile(obj, fptr);
    if (NIL_P(fptr->pathv)) return Qnil;
    if (lstat(RSTRING_PTR(fptr->pathv), &st) == -1) {
        rb_sys_fail_path(fptr->pathv);
    }
    return stat_new(&st);
#else
    return rb_io_stat(obj);
#endif
}
             
            Returns the modification time for file.
File.new("testfile").mtime #=> Wed Apr 09 08:53:14 CDT 2003
 
               static VALUE
rb_file_mtime(VALUE obj)
{
    rb_io_t *fptr;
    struct stat st;
    GetOpenFile(obj, fptr);
    if (fstat(fptr->fd, &st) == -1) {
        rb_sys_fail_path(fptr->pathv);
    }
    return stat_mtime(&st);
}
             
            Returns the pathname used to create file as a string. Does not normalize the name.
File.new("testfile").path #=> "testfile" File.new("/tmp/../tmp/xxx", "w").path #=> "/tmp/../tmp/xxx"
 
               static VALUE
rb_file_path(VALUE obj)
{
    rb_io_t *fptr;
    fptr = RFILE(rb_io_taint_check(obj))->fptr;
    rb_io_check_initialized(fptr);
    if (NIL_P(fptr->pathv)) return Qnil;
    return rb_obj_taint(rb_str_dup(fptr->pathv));
}
             
            Returns the pathname used to create file as a string. Does not normalize the name.
File.new("testfile").path #=> "testfile" File.new("/tmp/../tmp/xxx", "w").path #=> "/tmp/../tmp/xxx"
 
               static VALUE
rb_file_path(VALUE obj)
{
    rb_io_t *fptr;
    fptr = RFILE(rb_io_taint_check(obj))->fptr;
    rb_io_check_initialized(fptr);
    if (NIL_P(fptr->pathv)) return Qnil;
    return rb_obj_taint(rb_str_dup(fptr->pathv));
}
             
            Truncates file to at most integer bytes. The file must be opened for writing. Not available on all platforms.
f = File.new("out", "w") f.syswrite("1234567890") #=> 10 f.truncate(5) #=> 0 f.close() #=> nil File.size("out") #=> 5
 
               static VALUE
rb_file_truncate(VALUE obj, VALUE len)
{
    rb_io_t *fptr;
    off_t pos;
    rb_secure(2);
    pos = NUM2OFFT(len);
    GetOpenFile(obj, fptr);
    if (!(fptr->mode & FMODE_WRITABLE)) {
        rb_raise(rb_eIOError, "not opened for writing");
    }
    rb_io_flush(obj);
#ifdef HAVE_FTRUNCATE
    if (ftruncate(fptr->fd, pos) < 0)
        rb_sys_fail_path(fptr->pathv);
#else
# ifdef HAVE_CHSIZE
    if (chsize(fptr->fd, pos) < 0)
        rb_sys_fail(fptr->pathv);
# else
    rb_notimplement();
# endif
#endif
    return INT2FIX(0);
}