—

              
package SPVM::Sys;
our $VERSION = "0.532";
1;
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=head1 Name
SPVM::Sys - System Calls for File IO, Sockets, Time, Process, Signals, Users
=head1 Description
Sys class in L<SPVM> has methods to call system calls for file IO, sockets, user manipulation, process manipulation, and time.
=head1 Usage
  use Sys;
   
  my $fd_ref = [(Sys::IO::FileStream)undef];
  my $file = "a.txt";
  Sys->open($fd_ref, "<", $file);
   
  Sys->mkdir("foo");
   
  Sys->rmdir("foo");
   
  my $env_path = Sys->env("PATH");
   
  my $process_id = Sys->process_id;
=head1 Class Methods
=head2 STDIN
C<static method STDIN : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream> ();>
Returns the L<stdin|SPVM::Document::NativeAPI/"spvm_stdin"> opened by the SPVM language.
=head2 STDOUT
C<static method STDOUT : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream> ();>
Returns the L<stdout|SPVM::Document::NativeAPI/"spvm_stdout"> opened by the SPVM language.
=head2 STDERR
C<static method STDERR : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream> ();>
Returns the L<stderr|SPVM::Document::NativeAPI/"spvm_stderr"> opened by the SPVM language.
=head2 open
C<static method open : void ($stream_ref : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>[], $open_mode : string, $file : string);>
Opens a file given the open mode $open_mode and the file name $file. 
The opened file stream is set to $stream_ref at index 0.
The open mode $open_mode is replaced to a representation of the L<fopen|https://linux.die.net/man/3/fopen> function before calling the L<fopen|https://linux.die.net/man/3/fopen> function.
  [$open_mode]   [The mode of the fopen function]
  <              rb
  >              wb
  >>             wa
  +<             r+b
  +>             w+b
  +>>            a+b
If the system supports C<FD_CLOEXEC>, this flag is set to the opened file's file descriptor using L</"fcntl">.
Exceptions:
$stream_ref must be defined. Otherwise an exception is thrown.
The length of $stream_ref must be equal to 1. Otherwise an exception is thrown.
Exceptions thrown by L<Sys::IO#fopen|SPVM::Sys::IO/"fopen"> method could be thrown.
=head2 fdopen
C<static method fdopen : void ($stream_ref : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>[], $open_mode : string, $fd : int);>
Same as L</"open"> method except that this method takes the file descriptor $fd instead of the file name .
=head2 fileno
C<static method fileno : int ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>);>
Return the file descriptor of the file stream $stream.
This method calls L<Sys::IO#fileno|SPVM::Sys::IO/"fileno"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#fileno|SPVM::Sys::IO/"fileno"> method could be thrown.
=head2 read
C<static method read : int ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>, $buffer : mutable string, $length : int, $buffer_offset : int = 0);>
Reads data from the file stream $stream by the $length, and saves it to the buffer $buffer at offset $buffer_offset.
This method calls L<Sys::IO#fread|SPVM::Sys::IO/"fread"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#fread|SPVM::Sys::IO/"fread"> method could be thrown.
=head2 eof
C<static method eof : int ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>);>
Checks if the file stream $stream reasches the end of the file.
If it does, returns 1, otherwise returns 0.
This method calls L<Sys::IO#feof|SPVM::Sys::IO/"feof"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#feof|SPVM::Sys::IO/"feof"> method could be thrown.
=head2 readline
C<static method readline : mutable string ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>);>
Reads a line from th file stream $stream and returns it.
This method calls L<Sys::IO#feof|SPVM::Sys::IO/"readline"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by the L</"getc"> method could be thrown.
=head2 getc
C<static method getc : int ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>);>
Gets a charactor from the file stream $stream and returns it.
This method calls L<Sys::IO#getc|SPVM::Sys::IO/"getc"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#getc|SPVM::Sys::IO/"getc"> method could be thrown.
=head2 print
C<static method print : void ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>, $string : string);>
Prints the string $string to the file stream $stream.
This method calls L<Sys::IO#fwrite|SPVM::Sys::IO/"fwrite"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#fwrite|SPVM::Sys::IO/"fwrite"> method could be thrown.
=head2 printf
C<static method printf : void ($stream, $format : string, $args : object[])>
Prints the format string $string given the arguments $args to the file stream $stream.
Exceptions thrown by the L<"print"> method class could be thrown.
=head2 say
C<static method say : void ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>, $string : string);>
Prints the string $string and "\n" to the file stream $stream.
Exceptions:
Exceptions thrown by the L<"print"> method class could be thrown.
=head2 close
C<static method close : void ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>);>
Closes the file stream $stream.
This method calls L<Sys::IO#fclose|SPVM::Sys::IO/"fclose"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#fclose|SPVM::Sys::IO/"fclose"> method could be thrown.
=head2 seek
C<static method seek : void ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>, $offset : long, $whence : int);>
Moves the read/write position pointed to by the file stream $stream to the offset $offset given $whence.
See L<Sys::IO::Constant|SPVM::Sys::IO::Constant> about constant values given to $whence.
This method calls L<Sys::IO#fseek|SPVM::Sys::IO/"fseek"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#fseek|SPVM::Sys::IO/"fseek"> method could be thrown.
=head2 tell
C<static method tell : long ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>);>
Returns the read/write position pointed to by the file stream $stream.
This method calls L<Sys::IO#ftell|SPVM::Sys::IO/"ftell"> method.
Exceptions:
The file stream $stream must be defined. Otherwise an exception is thrown.
If the file stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#ftell|SPVM::Sys::IO/"ftell"> method could be thrown.
=head2 sysopen
C<static method sysopen : void ($fd_ref : int*, $file : string, $flags : int, $mode : int = 0);>
Opens a file given, the file path $file, the mode $flags and the mode $mode.
The file descriptor of the opened file is set to the value reffered by $fd_ref.
See L<Sys::IO::Constant|SPVM::Sys::IO::Constant> about constant values given to the flags $flags and the mode $mode.
Exceptions:
Exceptions thrown by L<Sys::IO#open|SPVM::Sys::IO/"open"> method could be thrown.
=head2 sysread
C<static method sysread : int ($fd : int, $buffer : mutable string, $length : int, $buffer_offset : int = 0);>
Reads data from the file stream $stream by the $length, and saves it to the buffer $buffer from the offset $buffer_offset.
Exceptions:
Exceptions thrown by L<Sys::IO#read|SPVM::Sys::IO/"read"> method could be thrown.
=head2 syswrite
C<static method syswrite : int ($fd : int, $buffer : string, $length : int = -1, $buffer_offset : int = 0);>
Writes data to the file stream $stream by the $length from the buffer $buffer at offset $buffer_offset.
Exceptions:
Exceptions thrown by L<Sys::IO#write|SPVM::Sys::IO/"write"> method could be thrown.
=head2 sysseek
C<static method sysseek : long ($fd : int, $offset : long, $whence : int);>
Moves the read/write position pointed to by the file descriptor $fd to the offset $offset given $whence.
See L<Sys::IO::Constant|SPVM::Sys::IO::Constant> about constant values given to $whence.
Exceptions:
Exceptions thrown by L<Sys::IO#lseek|SPVM::Sys::IO/"lseek"> method could be thrown.
=head2 fcntl
C<static method fcntl : int ($fd : int, $command : int, $command_arg : object of Int|SPVM::Sys::IO::Flock|object = undef);>
Calls L<Sys::IO#fcntl|SPVM::Sys::IO/"fcntl"> method and its return value.
Exceptions:
Exceptions thrown by L<Sys::IO#fcntl|SPVM::Sys::IO/"fcntl"> method could be thrown.
=head2 flock
C<static method flock : void ($fd : int, $operation : int);>
Locks the file specified by the file descriptor $fd given the operation $operation.
See L<Sys::IO::Constant|SPVM::Sys::IO::Constant> about constant values given to the operation $operation.
Exceptions:
Exceptions thrown by L<Sys::IO#flock|SPVM::Sys::IO/"flock"> method could be thrown.
=head2 mkdir
C<static method mkdir : void ($dir : string, $mode : int = -1);>
Creates the directory given the path $dir and the mode $mode.
If $mode is less than 0, $mode is set to 0777.
The permissions of the created directory are ($mode & ~L<umask|/"umask"> & 0777).
In Windows, the mode $mode is ignored.
Exceptions:
Exceptions thrown by L<Sys::IO#mkdir|SPVM::Sys::IO/"mkdir"> method could be thrown.
=head2 umask
C<static method umask : int ($mode : int);>
Sets the umask for the process to the mode $mode and returns the previous value.
Exceptions:
Exceptions thrown by L<Sys::IO#umask|SPVM::Sys::IO/"umask"> method could be thrown.
=head2 unlink
C<static method unlink : void ($file : string);>
Deletes a file.
In Windows, this method calls L<Sys::IO::Windows#unlink|SPVM::Sys::IO::Windows/"unlink"> method , otherwise calls L<Sys::IO#unlink|SPVM::Sys::IO/"unlink"> method.
Exceptions:
Exceptions thrown by the L<Sys::IO::Windows#unlink|SPVM::Sys::IO::Windows/"unlink"> method or L<Sys::IO#unlink|SPVM::Sys::IO/"unlink"> method could be thrown.
=head2 rename
C<static method rename : void ($old_path : string, $new_path : string);>
Raname the file name from the old name $old_path to the new name $new_path.
In Windows, this method calls L<Sys::IO::Windows#rename|SPVM::Sys::IO::Windows/"rename"> method , otherwise calls L<Sys::IO#rename|SPVM::Sys::IO/"rename"> method.
Exceptions:
Exceptions thrown by the L<Sys::IO::Windows#rename|SPVM::Sys::IO::Windows/"rename"> method or L<Sys::IO#rename|SPVM::Sys::IO/"rename"> method could be thrown.
=head2 rmdir
C<static method rmdir : void ($dir : string);>
Deletes the directory given the path $dir.
Exceptions:
Exceptions thrown by L<Sys::IO#rmdir|SPVM::Sys::IO/"rmdir"> method could be thrown.
=head2 chdir
C<static method chdir : void ($dir : string);>
Changes the working directory to the path $dir.
Exceptions:
Exceptions thrown by L<Sys::IO#chdir|SPVM::Sys::IO/"chdir"> method could be thrown.
=head2 chmod
C<static method chmod : void ($mode :int, $file : string);>
Changes the permissions of the file $file to the permission $mode.
Exceptions:
Exceptions thrown by L<Sys::IO#chmod|SPVM::Sys::IO/"chmod"> method could be thrown.
=head2 chown
C<static method chown : void ($owner : int, $group : int, $file : string);>
Changes the owner and the group of the file $file to $owner and $group.
Exceptions:
Exceptions thrown by L<Sys::IO#chown|SPVM::Sys::IO/"chown"> method could be thrown.
=head2 readlink
C<static method readlink : int ($file : string);>
Returns the content of the symbolic link file $file.
In Windows thie method calls L<Sys::IO::Windows#readlink|SPVM::Sys::IO::Windows/"readlink"> method , otherwise calls L<Sys::IO#readlink|SPVM::Sys::IO/"readlink"> method .
Exceptions:
Exceptions thrown by L<Sys::IO#readlink|SPVM::Sys::IO/"readlink"> method or L<Sys::IO::Windows#readlink|SPVM::Sys::IO::Windows/"readlink"> method could be thrown.
=head2 symlink
C<static method symlink : int ($old_path : string, $new_path : string);>
Creates a path $new_path symbolically linked to the path $old_path.
In Windows thie method calls L<Sys::IO::Windows#symlink|SPVM::Sys::IO::Windows/"symlink"> method , otherwise calls L<Sys::IO#symlink|SPVM::Sys::IO/"symlink"> method .
Exceptions:
Exceptions thrown by L<Sys::IO#symlink|SPVM::Sys::IO/"symlink"> method or L<Sys::IO::Windows#symlink|SPVM::Sys::IO::Windows/"symlink"> method could be thrown.
=head2 truncate
C<static method truncate : void ($fd : int, $legnth : long);>
Truncates the file referenced by the file descriptor $fd to a size of precisely length bytes $legnth.
Exceptions:
Exceptions thrown by L<Sys::IO#ftruncate|SPVM::Sys::IO/"ftruncate"> method could be thrown.
=head2 opendir
C<static method opendir : void ($dir_stream_ref : L<Sys::IO::DirStream|SPVM::Sys::IO::DirStream>[], $dir : string);>
Opens the directory stream given the directory $dir.
The opened directory stream is set to $dir_stream_ref at index 0.
Exceptions:
If the directory stream \$dir_stream is already closed, an exception is thrown.
This method calls L<Sys::IO#opendir|SPVM::Sys::IO/"opendir"> method.
Exceptions thrown by L<Sys::IO#opendir|SPVM::Sys::IO/"opendir"> method could be thrown.
=head2 closedir
C<static method closedir : void ($dir_stream : L<Sys::IO::DirStream|SPVM::Sys::IO::DirStream>);>
Closes the directory stream given the directory stream $dir_stream.
This method calls L<Sys::IO#closedir|SPVM::Sys::IO/"closedir"> method.
Exceptions:
If the directory stream \$dir_stream is already closed, an exception is thrown.
Exceptions thrown by L<Sys::IO#closedir|SPVM::Sys::IO/"closedir"> method could be thrown.
=head2 readdir
C<static method readdir : L<Sys::IO::Dirent|SPVM::Sys::IO::Dirent> ($dir_stream : L<Sys::IO::DirStream|SPVM::Sys::IO::DirStream>);>
Reads a directory entry from the dirctory stream $dir_stream.
This method calls L<Sys::IO#readdir|SPVM::Sys::IO/"readdir"> method.
Exceptions:
If the directory stream \$dir_stream is already closed, an exception is thrown.
Exceptions thrown by L<Sys::IO#readdir|SPVM::Sys::IO/"readdir"> method could be thrown.
=head2 rewinddir
C<static method rewinddir : void ($dir_stream : L<Sys::IO::DirStream|SPVM::Sys::IO::DirStream>);>
Resets the position of the directory stream $dir_stream to the beginning of the directory.
This method calls L<Sys::IO#rewinddir|SPVM::Sys::IO/"rewinddir"> method.
Exceptions:
If the directory stream \$dir_stream is already closed, an exception is thrown.
Exceptions thrown by L<Sys::IO#rewinddir|SPVM::Sys::IO/"rewinddir"> method could be thrown.
=head2 seekdir
C<static method seekdir : void ($dir_stream : L<Sys::IO::DirStream|SPVM::Sys::IO::DirStream>, $offset : long);>
Sets the current location associated with the directory stream $dir_stream to the offset $offset.
This method calls L<Sys::IO#seekdir|SPVM::Sys::IO/"seekdir"> method.
Exceptions:
If the directory stream \$dir_stream is already closed, an exception is thrown.
Exceptions thrown by L<Sys::IO#seekdir|SPVM::Sys::IO/"seekdir"> method could be thrown.
=head2 telldir
C<static method telldir : long ($dir_stream : L<Sys::IO::DirStream|SPVM::Sys::IO::DirStream>);>
Returns the current location associated with the directory stream $dir_stream.
This method calls L<Sys::IO#telldir|SPVM::Sys::IO/"telldir"> method.
Exceptions:
If the directory stream \$dir_stream is already closed, an exception is thrown.
Exceptions thrown by L<Sys::IO#telldir|SPVM::Sys::IO/"telldir"> method could be thrown.
=head2 popen
C<static method popen : void ($stream_ref : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>[], $open_mode : string, $command : string);>
Opens a file stream that joins a process by creating a pipe given the command $command and the open mode $open_mode.
The opened file stream is set to $stream_ref at index 0.
The open mode $open_mode is replaced to a representation of the L<fopen|https://linux.die.net/man/3/fopen> function before calling the L<fopen|https://linux.die.net/man/3/fopen> function.
  [$open_mode]   [The mode of the fopen function]
  |-             wb
  -|             rb
If the system supports C<FD_CLOEXEC>, this flag is set to the opened file's file descriptor using L</"fcntl">.
Exceptions:
Exceptions thrown by L<Sys::IO#popen|SPVM::Sys::IO/"popen"> method or L<Sys::IO#_popen|SPVM::Sys::IO/"_popen"> method could be thrown.
=head2 pclose
C<static method pclose : void ($stream : L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>);>
Closes the file stream $stream created by the L</"popen"> method.
This method calls L<Sys::IO#pclose|SPVM::Sys::IO/"pclose"> method or L<Sys::IO#_pclose|SPVM::Sys::IO/"_pclose">.
Exceptions:
The pipe stream $stream must be defined. Otherwise an exception is thrown.
If the pipe stream $stream is already closed,  an exception is thrown.
Exceptions thrown by L<Sys::IO#pclose|SPVM::Sys::IO/"pclose"> method or L<Sys::IO#_pclose|SPVM::Sys::IO/"_pclose"> method could be thrown.
=head2 select
C<static method select : int ($read_fds : L<Sys::Select::Fd_set|SPVM::Sys::Select::Fd_set>, $write_fds : L<Sys::Select::Fd_set|SPVM::Sys::Select::Fd_set>, $except_fds : L<Sys::Select::Fd_set|SPVM::Sys::Select::Fd_set>, $timeout : double = 0);>
Calls L<Sys::Select#select|SPVM::Sys::Select/"select"> method and returns its return value.
If $timeout is greter than or equal to 0, it is converted to a L<Sys::Time::Timeval|SPVM::Sys::Time::Timeval> object. Otherwise is converted to undef.
$nfds is set to 1024.
Exceptions:
Exceptions thrown by L<Sys::Select#select|SPVM::Sys::Select/"select"> method method could be thrown.
=head2 ioctl
C<static method ioctl : int ($fd : int, $request : int, $request_arg_ref : object of byte[]|short[]|int[]|long[]|float[]|double[]|object = undef);>
Windows:
Calls L<Sys::Ioctl#ioctlsocket|SPVM::Sys::Ioctl/"ioctlsocket"> method and returns its return value.
OSs other than Windows:
Calls L<Sys::Ioctl#ioctl|SPVM::Sys::Ioctl/"ioctl"> method and returns its return value.
Exceptions:
Exceptions thrown by the L<Sys::Ioctl#ioctl|SPVM::Sys::Ioctl/"ioctl"> method or L<Sys::Ioctl#ioctlsocket|SPVM::Sys::Ioctl/"ioctlsocket"> method could be thrown.
=head2 A
C<static method A : double ($file : string);>
Returns script start time minus file access time of the file $file, in days.
This method corresponds to Perl's  L<-A|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
The exceptions thrown by L</"stat"> method could be thrown.
=head2 C
C<static method C : double ($file : string);>
Returns script start time minus file inode change time of the file $file, in days.
This method corresponds to Perl's  L<-C|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
The exceptions thrown by L</"stat"> method could be thrown.
=head2 M
C<static method M : double ($file : string);>
Returns script start time minus file modification time of the file $file, in days.
This method corresponds to Perl's  L<-M|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
The exceptions thrown by L</"stat"> method could be thrown.
=head2 O
C<static method O : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Othersize if the file $file is owned by real uid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-O|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 R
C<static method R : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Otherwise if the file $file is readable by real uid/gid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-R|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 S
C<static method S : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Otherwise if the file $file is a socket, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-S|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 W
C<static method W : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Otherwise if the file $file is writable by real uid/gid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-W|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 X
C<static method X : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Otherwise if the file $file is executable by real uid/gid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-X|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 b
C<static method b : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Otherwise if the file $file is a block special file, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-b|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 c
C<static method c : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Otherwise if the file $file is a character special file, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-c|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 d
C<static method d : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
Otherwise if the file $file is a directory, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-d|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 e
C<static method e : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value. 
This method corresponds to Perl's  L<-e|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 f
C<static method f : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file is a plain file, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-f|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 g
C<static method g : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file has setgid bit set, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-g|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 k
C<static method k : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file has sticky bit set, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-k|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 l
C<static method l : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by the L</"lstat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file is a symbolic link (false if symlinks aren't supported by the file system), returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-l|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 o
C<static method o : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file is owned by effective uid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-l|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 p
C<static method p : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file is a named pipe (FIFO), or Filehandle is a pipe, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-p|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 r
C<static method r : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file is readable by effective uid/gid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-r|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 s
C<static method s : long ($file : string);>
If the file $file has nonzero size, returns its size in bytes, otherwise returns 0.
This method corresponds to Perl's  L<-s|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
The exceptions thrown by L</"stat"> method could be thrown.
=head2 u
C<static method u : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file has setuid bit set, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-u|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 w
C<static method w : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file is writable by effective uid/gid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-u|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 x
C<static method x : int ($file : string);>
If If the file doesn't exist or can't be examined(These checks are done by L</"stat"> method), returns 0 and L<errno|SPVM::Errno/"errno"> is set to a positive value.
Otherwise if the file $file is executable by effective uid/gid, returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-x|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
=head2 z
C<static method z : int ($file : string);>
If the file $file has zero size (is empty), returns 1, otherwise returns 0.
This method corresponds to Perl's  L<-z|https://perldoc.perl.org/functions/-X>.
Exceptions:
$file must be defined. Otherwise an exception is thrown.
The exceptions thrown by L</"stat"> method could be thrown.
=head2 time
C<static method time : long ();>
Returns the current epoch time.
=head2 localtime
C<static method localtime : L<Sys::Time::Tm|SPVM::Sys::Time::Tm> ($epoch : long = -1, $allow_minus = 0);>
Converts the epoch time $epoch to a L<Sys::Time::Tm|SPVM::Sys::Time::Tm> object, and returns it.
The return value is localized for the local time zone.
If $allow_minus is 0 and $epoch is less than 0, $epoch is set to the current epoch time.
=head2 gmtime
C<static method gmtime : L<Sys::Time::Tm|SPVM::Sys::Time::Tm> ($epoch : long = -1, $allow_minus = 0);>
Works just like L</"localtime">, but the returned values are for the UTC time zone.
=head2 utime
C<static method utime : void ($atime : long, $mtime : long, $file : string);>
Changes the access time and the modification time of the inode specified by the file $file given the access time $atime and the modification time $mtime.
If $atime < 0 and $mtime < 0, changes the access time and the modification time to the current time..
Exceptions:
Exceptions thrown by L<Sys::Time#utime|SPVM::Sys::Time/"utime"> method could be thrown.
=head2 stat
C<static method stat : L<Sys::IO::Stat|SPVM::Sys::IO::Stat> ($file : string);>
Returns information about a file $file.
Exceptions:
Exceptions thrown by L<Sys::IO::Stat#stat|SPVM::Sys::IO::Stat/"stat"> method could be thrown.
=head2 lstat
C<static method lstat : L<Sys::IO::Stat|SPVM::Sys::IO::Stat> ($file : string);>
Identical to L</"stat">, except that if path $file is a symbolic link(or directory junction only in Windows), then the link itself is stat-ed, not the file that it refers to.
In Windows, this method calls the L<lstat|SPVM::Sys::IO::Windows/"lstat"> method, otherwise calls the L<lstat|SPVM::Sys::IO::Stat/"lstat"> method.
Exceptions:
Exceptions thrown by L<Sys::IO::Stat#lstat|SPVM::Sys::IO::Stat/"lstat"> method or L<Sys::IO::Windows#lstat|SPVM::Sys::IO::Windows/"lstat"> method could be thrown.
=head2 fstat
C<static method fstat : L<Sys::IO::Stat|SPVM::Sys::IO::Stat> ($fd : int);>
Identical to L</"stat">, except that the file to be stat-ed is specified by the file descriptor $fd.
Exceptions:
Exceptions thrown by L<Sys::IO::Stat#fstat|SPVM::Sys::IO::Stat/"fstat"> method could be thrown.
=head2 env
C<static method env : string ($name : string);>
Gets an environment variable with the name $name.
=head2 set_env
C<static method set_env : void ($name : string, $value : string);>
Sets an environment variable with the name $name and the value $value.
If $value is undef or "", the environment variable is removed.
Exceptions:
This method calls the following methods, so exceptions thrown by these methods could be thrown.
=over 2
=item * L<_putenv_s|SPVM::Sys::Env/"_putenv_s"> in Sys::Env
=item * L<setenv|SPVM::Sys::Env/"setenv"> in Sys::Env
=item * L<unsetenv|SPVM::Sys::Env/"unsetenv"> in Sys::Env
=back
=head2 osname
C<static method osname : string ()>
Gets the OS name. This method corresponds to Perl's L<$^O|https://perldoc.perl.org/perlvar#$%5EO>.
=over 2
=item * C<linux>
=item * C<darwin>
=item * C<MSWin32>
=item * C<freebsd>
=item * C<openbsd>
=item * C<solaris>
=back
Exceptions:
If the OS name could not be determined, an exception is thrown.
=head2 socket
C<static method socket : void ($socket_fd_ref : int*, $domain : int, $type : int, $protocol : int);>
Opens a socket given the domain $domain, the type $type, and the protocal $protocol.
The created socket file descriptor is set to the value referenced by $socket_fd_ref.
This method calls L<Sys::Socket#socket|SPVM::Sys::Socket/"socket"> method.
If the system supports C<FD_CLOEXEC>, this flag is set to the value referenced by $socket_fd_ref using L</"fcntl">.
Exceptions:
Exceptions thrown by L<Sys::Socket#socket|SPVM::Sys::Socket/"socket"> method could be thrown.
=head2 connect
C<static method connect : void ($socket_fd : int, $sockaddr : L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr>);>
Attempts to connect to a remote socket, just like the C<connect> system call.
This method calls L<Sys::Socket#connect|SPVM::Sys::Socket/"connect"> method.
Exceptions:
Exceptions thrown by L<Sys::Socket#connect|SPVM::Sys::Socket/"connect"> method could be thrown.
=head2 bind
C<static method bind : void ($socket_fd : int, $sockaddr : L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr>);>
Binds a network address $sockaddr to the socket $socket_fd.
This method calls L<Sys::Socket#bind|SPVM::Sys::Socket/"bind"> method.
Exceptions:
Exceptions thrown by L<Sys::Socket#bind|SPVM::Sys::Socket/"bind"> method could be thrown.
=head2 listen
C<static method listen : void ($socket_fd : int, $backlog : int);>
Does the same thing that the C<listen> system call does.
This method calls L<Sys::Socket#listen|SPVM::Sys::Socket/"listen"> method.
Exceptions:
Exceptions thrown by L<Sys::Socket#listen|SPVM::Sys::Socket/"listen"> method could be thrown.
=head2 accept
C<static method accept : L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr> ($client_fd_ref : int*, $server_fd : int);>
Performs accept operation.
Implementation:
Thie methods calls L<Sys::Socket#accept|SPVM::Sys::Socket/"accept"> method given the file descriptor $server_fd, a client address for output, the size of the client address.
The client address for output and the size of the client address are automatically created.
$$client_fd_ref is set to the return value.
The client address is upgraded to a child class of the L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr> using L<upgrade|SPVM::Sys::Socket::Sockaddr/"upgrade"> method.
If the system supports C<FD_CLOEXEC>, The file descriptor flag of $$client_fd_ref is set to C<FD_CLOEXEC> using L</"fcntl"> method.
Exceptions:
Exceptions thrown by L<Sys::Socket#accept|SPVM::Sys::Socket/"accept"> method could be thrown.
=head2 recv
C<static method recv : int ($socket_fd : int, $buffer : mutable string, $length : int, $flags : int, $buffer_offset : int = 0);>
Receives a message on a socket.
This method calls L<Sys::Socket#recv|SPVM::Sys::Socket/"recv"> method given the arguments given to this method and returns its return value.
Exceptions:
Exceptions thrown by L<Sys::Socket#recv|SPVM::Sys::Socket/"recv"> method could be thrown.
=head2 recvfrom
C<static method recvfrom : int ($socket_fd : int, $buffer : mutable string, $length : int, $flags : int, $sockaddr_ref : L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr>[], $buffer_offset : int = 0);>
Receives a message on a socket given the array $sockaddr_ref for a peer socket address for output.
This method calls L<Sys::Socket#recvfrom|SPVM::Sys::Socket/"recvfrom"> method given the arguments given to this method and returns its return value.
$addrlen_ref is set to an int reference.
If $sockaddr_ref is given, $sockaddr is set to a L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr> object.
In this case, $sockaddr is upgraded by calling L<Sys::Socket::Sockaddr#upgrade|SPVM::Sys::Socket::Sockaddr/"upgrade"> method and $sockaddr_ref at index 0 is set to it.
Exceptions:
If $sockaddr_ref for an array for a peer socket address for output is defined, the length must be 1.
Exceptions thrown by L<Sys::Socket#recvfrom|SPVM::Sys::Socket/"recvfrom"> method could be thrown.
=head2 send
C<static method send : int ($socket_fd : int, $buffer : string, $flags : int, $length : int = -1, $buffer_offset : int = 0);>
Sends a message on a socket.
This method calls L<Sys::Socket#send|SPVM::Sys::Socket/"send"> method given the arguments given to this method and returns its return value.
If $length is less than 0, $length is set to the length of $buffer.
Exceptions:
Exceptions thrown by L<Sys::Socket#sendto|SPVM::Sys::Socket/"send"> method could be thrown.
=head2 sendto
C<static method sendto : int ($socket_fd : int, $buffer : string, $flags : int, $sockaddr : L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr>, $length : int = -1, $buffer_offset : int = 0);>
Sends a message on a socket given the peer socket address $sockaddr.
This method calls L<Sys::Socket#sendto|SPVM::Sys::Socket/"sendto"> method given the arguments given to this method and returns its return value.
If $length is less than 0, $length is set to the length of $buffer.
Exceptions:
Exceptions thrown by L<Sys::Socket#sendto|SPVM::Sys::Socket/"sendto"> method could be thrown.
=head2 shutdown
C<static method shutdown : void ($socket_fd : int, $how : int);>
Shuts down a socket  connection $socket_fd in the manner indicated by $how.
This method calls L<Sys::Socket#shutdown|SPVM::Sys::Socket/"shutdown"> method.
Exceptions:
Exceptions thrown by L<Sys::Socket#shutdown|SPVM::Sys::Socket/"shutdown"> method could be thrown.
=head2 getpeername
C<static method getpeername : L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr> ($socket_fd : int);>
Returns the packed sockaddr address of the other end of the socket connection $socket_fd.
This method calls L<Sys::Socket#getpeername|SPVM::Sys::Socket/"getpeername"> method.
The returned packed sockaddr address is upgraded to a child class of the L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr> using L<upgrade|SPVM::Sys::Socket::Sockaddr/"upgrade"> method.
Exceptions:
Exceptions thrown by L<Sys::Socket#getpeername|SPVM::Sys::Socket/"getpeername"> method could be thrown.
=head2 getsockname
C<static method getsockname : L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr> ($socket_fd : int)>
Returns the packed sockaddr address of this end of the socket connection $socket_fd.
             
Thie method calls L<Sys::Socket#getsockname|SPVM::Sys::Socket/"getsockname"> method.
The returned packed sockaddr address is upgraded to a child class of the L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr> using L<upgrade|SPVM::Sys::Socket::Sockaddr/"upgrade"> method.
Exceptions:
Exceptions thrown by L<Sys::Socket#getsockname|SPVM::Sys::Socket/"getsockname"> method could be thrown.
=head2 socketpair
C<static method socketpair : void ($socket_fd1_ref : int*, $socket_fd2_ref : int*, $domain : int, $type : int, $protocol : int);>
Creates an unnamed pair of sockets in the specified domain, of
the specified type. The domain $domain, the type $type, the protocal $protocol are specified the
same as for the syscall of the same name.
The opened reading file descripor is set to the value referenced by $socket_fd1_ref.
The opened writing file descripor is set to the value referenced by $socket_fd2_ref.
This method calls L<Sys::Socket#socketpair|SPVM::Sys::Socket/"socketpair"> method .
If available, C<FD_CLOEXEC> is set to the file descriptor of the value referenced by $socket_fd1_ref and the value referenced by $socket_fd2_ref.
Exceptions:
Exceptions thrown by L<Sys::Socket#socketpair|SPVM::Sys::Socket/"socketpair"> method could be thrown.
=head2 setsockopt
C<static method setsockopt : void ($socket_fd : int, $level : int, $option_name : int, $option_value : object of string|Int);>
Sets the socket option requested.
This method calls L<Sys::Socket#getsockopt|SPVM::Sys::Socket/"getsockopt"> method.
Exceptions:
$option_value must be defined. Otherwise an exception is thrown.
The type of \$option_value must be the Int or string type.
Exceptions thrown by L<Sys::Socket#getsockopt|SPVM::Sys::Socket/"getsockopt"> method could be thrown.
=head2 getsockopt
C<static method getsockopt : string ($socket_fd : int, $level : int, $option_name : int, $option_value_length : int = -1);>
If $option_value_length is less than 0, it is set to 4.
This method calls L<Sys::Socket#getsockopt|SPVM::Sys::Socket/"getsockopt"> method.
Examples:
Getting an int value:
  my $reuseaddr_packed = Sys->getsockopt($socket, SOCKET->SOL_SOCKET, SOCKET->SO_REUSEADDR);
  my $reuseaddr_ref = [0];
  Fn->memcpy($reuseaddr_ref, 0, $reuseaddr_packed, 0, 4);
  my $reuseaddr = $reuseaddr_ref->[0];
Exceptions:
Exceptions thrown by L<Sys::Socket#getsockopt|SPVM::Sys::Socket/"getsockopt"> method could be thrown.
=head2 signal
C<static method signal : void ($signal_number : int, $handler_name : string);>
Sets a signal handler with its name $handler_name for the given signal number $signal_number.
If $handler_name is "DEFAULT", the signal handler is L<"SIG_DFL"|SPVM::Sys::Signal/"SIG_DFL">.
If $handler_name is "IGNORE", the signal handler is L<"SIG_IGN"|SPVM::Sys::Signal/"SIG_IGN">.
See L<Sys::Signal#signal|SPVM::Sys::Signal/"signal"> method in detail.
Exceptions:
If $handler_name is not available, an exception is thrown.
The exceptions thrown by L<Sys::Signal#signal|SPVM::Sys::Signal/"signal"> method could be thrown.
=head2 kill
C<static method kill : void ($signal_number : int, $process_id : int);>
Send a signal $signal_number to the process whose process ID is $process_id.
See L<Sys::Signal#kill|SPVM::Sys::Signal/"kill"> method in detail.
In Windows, see L<Sys::Signal#raise|SPVM::Sys::Signal/"raise"> method in detail.
Exceptions:
The exceptions thrown by L<Sys::Signal#alarm|SPVM::Sys::Signal/"alarm"> method could be thrown.
The exceptions thrown by L<Sys::Signal#raise|SPVM::Sys::Signal/"raise"> method could be thrown.
$process_id must be equal to Sys->process_id in Windows. Otherwise an exception is thrown.
=head2 alarm
C<static method alarm : int ($seconds : int);>
Sets a alarm signal sent after seconds $seconds.
See L<Sys::Signal#alarm|SPVM::Sys::Signal/"alarm"> method in detail.
Exceptions:
The exceptions thrown by L<Sys::Signal#alarm|SPVM::Sys::Signal/"alarm"> method could be thrown.
=head2 fork
C<static method fork : int ();>
Forks the process by calling L<Sys::Process#fork|SPVM::Sys::Process/"fork"> method.
It returns the child process ID to the parent process, or returns 0 to the child process.
Exceptions:
Exceptions thrown by L<Sys::Process#fork|SPVM::Sys::Process/"fork"> method could be thrown.
=head2 getpriority
C<static method getpriority : int ($which : int, $who : int);>
Return the scheduling priority of the process, process group, or user, as indicated by $which and $who is obtained.
Exceptions:
Exceptions thrown by L<Sys::Process#getpriority|SPVM::Sys::Process/"getpriority"> method could be thrown.
=head2 setpriority
C<static method setpriority : void ($which : int, $who : int, $priority : int)>
Sets the scheduling priority of the process, process group, or user, as indicated by $which and $who is obtained.
Exceptions:
Exceptions thrown by L<Sys::Process#setpriority|SPVM::Sys::Process/"setpriority"> method could be thrown.
=head2 sleep
C<static method sleep : int ($seconds : int);>
Sleeps for the seconds $seconds.
=head2 wait
C<static method wait : int ($wstatus_ref : int*);>
Waits for state changes in a child of the calling process, and returns a process ID whose state is changed.
The status about the child whose state has changed is set to $wstatus_ref.
The following methods in L<Sys::Process|SPVM::Sys::Process> class checks the value of $wstatus_ref.
=over 2
=item * L<WIFEXITED|SPVM::Sys::Process/"WIFEXITED">
=item * L<WEXITSTATUS|SPVM::Sys::Process/"WEXITSTATUS">
=item * L<WIFSIGNALED|SPVM::Sys::Process/"WIFSIGNALED">
=item * L<WTERMSIG|SPVM::Sys::Process/"WTERMSIG">
=item * L<WCOREDUMP|SPVM::Sys::Process/"WCOREDUMP">
=item * L<WIFEXITED|SPVM::Sys::Process/"WIFEXITED">
=item * L<WIFSTOPPED|SPVM::Sys::Process/"WIFSTOPPED">
=item * L<WSTOPSIG|SPVM::Sys::Process/"WSTOPSIG">
=item * L<WIFCONTINUED|SPVM::Sys::Process/"WIFCONTINUED">
=back
Exceptions:
Exceptions thrown by L<Sys::Process#wait|SPVM::Sys::Process/"wait"> method could be thrown.
=head2 waitpid
C<static method waitpid : int ($process_id : in, $options : int, $wstatus_ref : int*);>
Same as the L</"wait"> method, but can give the process ID $process_id and the options $options.
See L<Sys::Process::Constant|SPVM::Sys::Process::Constant> about constant values given to $options.
Exceptions:
Exceptions thrown by L<Sys::Process#waitpid|SPVM::Sys::Process/"waitpid"> method could be thrown.
=head2 system
C<static method system : int ($command : string);>
Executes a command specified in command using shell and return the L</"wait"> status.
=head2 exit
C<static method exit : void ($status : int);>
Terminates the calling process immediately with the status $status.
=head2 pipe
C<static method pipe : void ($read_fd_ref : int*, $write_fd_ref : int*);>
Opens a pair of pipes.
If the system supports C<FD_CLOEXEC>, this flag is set to the value referenced by $read_fd_ref and the value referenced by $write_fd_ref using L</"fcntl">.
=head2 getpgrp
C<static method getpgrp : int ($process_id : int);>
Gets the process group number given the process ID $process_id of the running this program.
=head2 setpgrp
C<static method setpgrp : void ($process_id : int, $process_group_id : int);>
Sets the process group number $process_group_id given the process ID $process_id of the running this program.
=head2 process_id
C<static method process_id : int ();>
Gets the process number of the running this program.
=head2 getppid
C<static method getppid : int ();>
Returns the process ID of the parent of the calling process.
=head2 exec
C<static method exec : void ($program : string, $args : string[] = undef);>
Executes the program $program with the arguments $args without using shell and never returns.
Examples:
  Sys->exec("/bin/echo", ["-n", "Hello"]);
=head2 real_user_id
C<static method real_user_id : int ();>
Gets the real user ID of the current process.
This method calls L<Sys::User#getuid|SPVM::Sys::User/"getuid"> method and returns its return value.
Exceptions:
Exceptions thrown by L<Sys::User#getuid|SPVM::Sys::User/"getuid"> method could be thrown.
=head2 effective_user_id
C<static method effective_user_id : int ();>
Gets the effective user ID of the current process.
This method calls L<Sys::User#geteuid|SPVM::Sys::User/"geteuid"> method and returns its return value.
Exceptions:
Exceptions thrown by L<Sys::User#geteuid|SPVM::Sys::User/"geteuid"> method could be thrown.
=head2 real_group_id
C<static method real_group_id : int ();>
Gets the real group ID of the current process.
This method calls L<Sys::User#getgid|SPVM::Sys::User/"getgid"> method and returns its return value.
Exceptions:
Exceptions thrown by L<Sys::User#getgid|SPVM::Sys::User/"getgid"> method could be thrown.
=head2 effective_group_id
C<static method effective_group_id : int ();>
Gets the effective group ID of the current process.
This method calls L<Sys::User#getegid|SPVM::Sys::User/"getegid"> method and returns its return value.
Exceptions:
Exceptions thrown by L<Sys::User#getegid|SPVM::Sys::User/"getegid"> method could be thrown.
=head2 set_real_user_id
C<static method set_real_user_id : void ($uid : int);>
Sets the real user ID of the current process.
This method calls L<Sys::User#setuid|SPVM::Sys::User/"setuid"> method given the argument given to this method.
Exceptions:
Exceptions thrown by L<Sys::User#setuid|SPVM::Sys::User/"setuid"> method could be thrown.
=head2 set_effective_user_id
C<static method set_effective_user_id : void ($euid : int);>
Sets the effective user ID of the current process.
This method calls L<Sys::User#seteuid|SPVM::Sys::User/"seteuid"> method given the argument given to this method.
Exceptions:
Exceptions thrown by L<Sys::User#seteuid|SPVM::Sys::User/"seteuid"> method could be thrown.
=head2 set_real_group_id
C<static method set_real_group_id : void ($real_group_id : int);>
Sets the real group ID of the current process.
This method calls L<Sys::User#setgid|SPVM::Sys::User/"setgid"> method given the argument given to this method.
Exceptions:
Exceptions thrown by L<Sys::User#setgid|SPVM::Sys::User/"setgid"> method could be thrown.
=head2 set_effective_group_id
C<static method set_effective_group_id : void ($effective_group_id : int);>
Sets the effective group ID of the current process.
This method calls L<Sys::User#getegid|SPVM::Sys::User/"getegid"> method given the argument given to this method.
Exceptions:
Exceptions thrown by L<Sys::User#getegid|SPVM::Sys::User/"getegid"> method could be thrown.
=head2 setpwent
C<static method setpwent : void ();>
Rewinds to the beginning of the password database.
=head2 endpwent
C<static method endpwent : void ();>
Closes the password database after all processing has been performed.
=head2 getpwent
C<static method getpwent : L<Sys::User::Passwd|SPVM::Sys::User::Passwd> ();>
Gets a next password entry.
=head2 setgrent
C<static method setgrent : void ();>
Rewinds to the beginning of the group database.
=head2 endgrent
C<static method endgrent : void ();>
Closes the group database after all processing has been performed.
=head2 getgrent
C<static method getgrent : L<Sys::User::Group|SPVM::Sys::User::Group> ();>
Gets a next group entry.
=head2 getgroups
C<static method getgroups : int[] ();>
Returns the supplementary group IDs of the calling process.
=head2 setgroups
C<static method setgroups : void ($group_ids : int[]);>
Sets the supplementary group IDs for the calling process.
=head2 getpwuid
C<static method getpwuid : L<Sys::User::Passwd|SPVM::Sys::User::Passwd> ($id : int);>
Searches a password entry given The user ID $id. If found, returns the password entry, otherwise return undef.
=head2 getpwnam
C<static method getpwnam : L<Sys::User::Passwd|SPVM::Sys::User::Passwd> ($name : string);>
Searches a password entry given The user name $name. If found, returns the password entry, otherwise return undef.
=head2 getgrgid
C<static method getgrgid : L<Sys::User::Group|SPVM::Sys::User::Group> ($id : int);>
Searches a group entry given The group ID $id. If found, returns the group entry, otherwise return undef.
=head2 getgrnam
C<static method getgrnam : L<Sys::User::Group|SPVM::Sys::User::Group> ($name : string);>
Searches a group entry given The group name $name. If found, returns the group entry, otherwise return undef.
=head2 srand
C<static method srand : void ($seed : int);>
Sets the random number $seed for L</"rand"> method.
Implementation:
Calls L<Fn#set_seed|SPVM::Fn/"set_seed"> method given $seed.
=head2 rand
C<static method rand : double ($max : int = 1);>
Returns a random fractional number greater than or equal to 0 and less than $max.
If you change the random seed, you can use L</"srand"> method.
Implementation:
If C<seed> stack variable is initialized, the random seed is got from the variable.
Otherwise the random seed is created from the process ID and epoch time.
And calls L<Fn#rand|SPVM::Fn/"rand"> method given the reference of the seed, $max.
And calls L</"srand"> method given the returned seed to update C<seed> stack variable.
Exceptions:
Exceptions thrown by L<Fn#rand|SPVM::Fn/"rand"> method could be thrown.
=head1 Modules
=over 2
=item * L<Sys::Env|SPVM::Sys::Env>
=item * L<Sys::IO|SPVM::Sys::IO>
=item * L<Sys::IO::Constant|SPVM::Sys::IO::Constant>
=item * L<Sys::Ioctl|SPVM::Sys::Ioctl>
=item * L<Sys::Ioctl::Constant|SPVM::Sys::Ioctl::Constant>
=item * L<Sys::IO::Dirent|SPVM::Sys::IO::Dirent>
=item * L<Sys::IO::DirStream|SPVM::Sys::IO::DirStream>
=item * L<Sys::IO::FileStream|SPVM::Sys::IO::FileStream>
=item * L<Sys::IO::Flock|SPVM::Sys::IO::Flock>
=item * L<Sys::IO::Stat|SPVM::Sys::IO::Stat>
=item * L<Sys::IO::Windows|SPVM::Sys::IO::Windows>
=item * L<Sys::OS|SPVM::Sys::OS>
=item * L<Sys::Poll|SPVM::Sys::Poll>
=item * L<Sys::Poll::Constant|SPVM::Sys::Poll::Constant>
=item * L<Sys::Poll::PollfdArray|SPVM::Sys::Poll::PollfdArray>
=item * L<Sys::Process|SPVM::Sys::Process>
=item * L<Sys::Process::Constant|SPVM::Sys::Process::Constant>
=item * L<Sys::Select|SPVM::Sys::Select>
=item * L<Sys::Select::Constant|SPVM::Sys::Select::Constant>
=item * L<Sys::Select::Fd_set|SPVM::Sys::Select::Fd_set>
=item * L<Sys::Signal|SPVM::Sys::Signal>
=item * L<Sys::Signal::Constant|SPVM::Sys::Signal::Constant>
=item * L<Sys::Signal::Handler|SPVM::Sys::Signal::Handler>
=item * L<Sys::Socket|SPVM::Sys::Socket>
=item * L<Sys::Socket::Addrinfo|SPVM::Sys::Socket::Addrinfo>
=item * L<Sys::Socket::AddrinfoLinkedList|SPVM::Sys::Socket::AddrinfoLinkedList>
=item * L<Sys::Socket::Constant|SPVM::Sys::Socket::Constant>
=item * L<Sys::Socket::Errno|SPVM::Sys::Socket::Errno>
=item * L<Sys::Socket::Error|SPVM::Sys::Socket::Error>
=item * L<Sys::Socket::Error::InetInvalidNetworkAddress|SPVM::Sys::Socket::Error::InetInvalidNetworkAddress>
=item * L<Sys::Socket::In6_addr|SPVM::Sys::Socket::In6_addr>
=item * L<Sys::Socket::In_addr|SPVM::Sys::Socket::In_addr>
=item * L<Sys::Socket::In_addr_base|SPVM::Sys::Socket::In_addr_base>
=item * L<Sys::Socket::Ip_mreq|SPVM::Sys::Socket::Ip_mreq>
=item * L<Sys::Socket::Ip_mreq_source|SPVM::Sys::Socket::Ip_mreq_source>
=item * L<Sys::Socket::Ipv6_mreq|SPVM::Sys::Socket::Ipv6_mreq>
=item * L<Sys::Socket::Sockaddr|SPVM::Sys::Socket::Sockaddr>
=item * L<Sys::Socket::Sockaddr::In|SPVM::Sys::Socket::Sockaddr::In>
=item * L<Sys::Socket::Sockaddr::In6|SPVM::Sys::Socket::Sockaddr::In6>
=item * L<Sys::Socket::Sockaddr::Storage|SPVM::Sys::Socket::Sockaddr::Storage>
=item * L<Sys::Socket::Sockaddr::Un|SPVM::Sys::Socket::Sockaddr::Un>
=item * L<Sys::Socket::Util|SPVM::Sys::Socket::Util>
=item * L<Sys::Time|SPVM::Sys::Time>
=item * L<Sys::Time::Constant|SPVM::Sys::Time::Constant>
=item * L<Sys::Time::Itimerval|SPVM::Sys::Time::Itimerval>
=item * L<Sys::Time::Timespec|SPVM::Sys::Time::Timespec>
=item * L<Sys::Time::Timeval|SPVM::Sys::Time::Timeval>
=item * L<Sys::Time::Timezone|SPVM::Sys::Time::Timezone>
=item * L<Sys::Time::Tm|SPVM::Sys::Time::Tm>
=item * L<Sys::Time::Tms|SPVM::Sys::Time::Tms>
=item * L<Sys::Time::Util|SPVM::Sys::Time::Util>
=item * L<Sys::Time::Utimbuf|SPVM::Sys::Time::Utimbuf>
=item * L<Sys::User|SPVM::Sys::User>
=item * L<Sys::User::Group|SPVM::Sys::User::Group>
=item * L<Sys::User::Passwd|SPVM::Sys::User::Passwd>
=back
=head1 Perl Modules
=over 2
=item * L<Test::SPVM::Sys::Socket>
=item * L<Test::SPVM::Sys::Socket::ServerManager>
=item * L<Test::SPVM::Sys::Socket::ServerManager::IP>
=item * L<Test::SPVM::Sys::Socket::ServerManager::UNIX>
=item * L<Test::SPVM::Sys::Socket::Server>
=item * L<Test::SPVM::Sys::Socket::Util>
=back
=head1 See Also
=over 2
=item * L<IO|SPVM::IO> - File IO, Sockets
=item * L<File::Spec|SPVM::File::Spec>
=item * L<File::Temp|SPVM::File::Temp>
=item * L<File::Copy|SPVM::File::Copy>
=item * L<File::Find|SPVM::File::Find>
=item * L<File::Glob|SPVM::File::Glob>
=item * L<Cwd|SPVM::Cwd>
=item * L<Time::HiRes|SPVM::Time::HiRes>
=item * L<Go|SPVM::Go>
=back
=head1 Repository
L<SPVM::Sys - Github|https://github.com/yuki-kimoto/SPVM-Sys>
=head1 Author
Yuki Kimoto(L<https://github.com/yuki-kimoto>)
=head1 Contributors
Gabor Szabo(L<https://github.com/szabgab>)
=head1 Copyright & License
Copyright (c) 2023 Yuki Kimoto
MIT License