- NAME
- SYNOPSIS
- DESCRIPTION
- REVISION

# NAME

VMS::Stdio - standard I/O functions via VMS extensions

# SYNOPSIS

      use VMS::Stdio qw( &flush &getname &remove &rewind &setdef &sync &tmpnam
                         &vmsopen &vmssysopen &waitfh &writeof );
      setdef("new:[default.dir]");
      $uniquename = tmpnam;
      $fh = vmsopen("my.file","rfm=var","alq=100",...) or die $!;
      $name = getname($fh);
      print $fh "Hello, world!\n";
      flush($fh);
      sync($fh);
      rewind($fh);
      $line = <$fh>;
      undef $fh;  # closes file
      $fh = vmssysopen("another.file", O_RDONLY | O_NDELAY, 0, "ctx=bin");
      sysread($fh,$data,128);
      waitfh($fh);
      close($fh);
      remove("another.file");
      writeof($pipefh);
      binmode($fh);

# DESCRIPTION

This package gives Perl scripts access via VMS extensions to several C stdio operations not available through Perl's CORE I/O functions. The specific routines are described below. These functions are prototyped as unary operators, with the exception of `vmsopen` and `vmssysopen`, which can take any number of arguments, and `tmpnam`, which takes none.

All of the routines are available for export, though none are exported by default. All of the constants used by `vmssysopen` to specify access modes are exported by default. The routines are associated with the Exporter tag FUNCTIONS, and the constants are associated with the Exporter tag CONSTANTS, so you can more easily choose what you'd like to import:

        # import constants, but not functions
        use VMS::Stdio;  # same as use VMS::Stdio qw( :DEFAULT );
        # import functions, but not constants
        use VMS::Stdio qw( !:CONSTANTS :FUNCTIONS );
        # import both
        use VMS::Stdio qw( :CONSTANTS :FUNCTIONS );
        # import neither
        use VMS::Stdio ();

Of course, you can also choose to import specific functions by name, as usual.

This package `ISA` IO::File, so that you can call IO::File methods on the handles returned by `vmsopen` and `vmssysopen`. The IO::File package is not initialized, however, until you actually call a method that VMS::Stdio doesn't provide. This is done to save startup time for users who don't wish to use the IO::File methods.

Note: In order to conform to naming conventions for Perl extensions and functions, the name of this package has been changed to VMS::Stdio as of Perl 5.002, and the names of some routines have been changed. Calls to the old VMS::stdio routines will generate a warning, and will be routed to the equivalent VMS::Stdio function. This compatibility interface will be removed in a future release of this extension, so please update your code to use the new routines.

binmode

  This function causes the file handle to be reopened with the CRTL's carriage control processing disabled; its effect is the same as that of the `b` access mode in `vmsopen`. After the file is reopened, the file pointer is positioned as close to its position before the call as possible (i.e. as close as fsetpos() can get it -- for some record-structured files, it's not possible to return to the exact byte offset in the file). Because the file must be reopened, this function cannot be used on temporary-delete files. `binmode` returns true if successful, and `undef` if not.

  Note that the effect of `binmode` differs from that of the binmode() function on operating systems such as Windows and MSDOS, and is not needed to process most types of file.

flush

  This function causes the contents of stdio buffers for the specified file handle to be flushed. If `undef` is used as the argument to `flush`, all currently open file handles are flushed. Like the CRTL fflush() routine, it does not flush any underlying RMS buffers for the file, so the data may not be flushed all the way to the disk. `flush` returns a true value if successful, and `undef` if not.

getname

  The `getname` function returns the file specification associated with a Perl I/O handle. If an error occurs, it returns `undef`.

remove

  This function deletes the file named in its argument, returning a true value if successful and `undef` if not. It differs from the CORE Perl function `unlink` in that it does not try to reset file protection if the original protection does not give you delete access to the file (cf. perlvms). In other words, `remove` is equivalent to

        unlink($file) if VMS::Filespec::candelete($file);

rewind

  `rewind` resets the current position of the specified file handle to the beginning of the file. It's really just a convenience method equivalent in effect to `seek($fh,0,0)`. It returns a true value if successful, and `undef` if it fails.

setdef

  This function sets the default device and directory for the process. It is identical to the built-in chdir() operator, except that the change persists after Perl exits. It returns a true value on success, and `undef` if it encounters an error.

sync

  This function flushes buffered data for the specified file handle from stdio and RMS buffers all the way to disk. If successful, it returns a true value; otherwise, it returns `undef`.

tmpnam

  The `tmpnam` function returns a unique string which can be used as a filename when creating temporary files. If, for some reason, it is unable to generate a name, it returns `undef`.

vmsopen

  The `vmsopen` function enables you to specify optional RMS arguments to the VMS CRTL when opening a file. Its operation is similar to the built-in Perl `open` function (see perlfunc for a complete description), but it will only open normal files; it cannot open pipes or duplicate existing I/O handles. Up to 8 optional arguments may follow the file name. These arguments should be strings which specify optional file characteristics as allowed by the CRTL. (See the CRTL reference manual description of creat() and fopen() for details.) If successful, `vmsopen` returns a VMS::Stdio file handle; if an error occurs, it returns `undef`.

  You can use the file handle returned by `vmsopen` just as you would any other Perl file handle. The class VMS::Stdio ISA IO::File, so you can call IO::File methods using the handle returned by `vmsopen`. However, `use`ing VMS::Stdio does not automatically `use` IO::File; you must do so explicitly in your program if you want to call IO::File methods. This is done to avoid the overhead of initializing the IO::File package in programs which intend to use the handle returned by `vmsopen` as a normal Perl file handle only. When the scalar containing a VMS::Stdio file handle is overwritten, `undef`d, or goes out of scope, the associated file is closed automatically.

  File characteristic options:

  alq=INTEGER

    Sets the allocation quantity for this file

  bls=INTEGER

    File blocksize

  ctx=STRING

    Sets the context for the file. Takes one of these arguments:

    bin

      Disables LF to CRLF translation

    cvt

      Negates previous setting of `ctx=noctx`

    nocvt

      Disables conversion of FORTRAN carriage control

    rec

      Force record-mode access

    stm

      Force stream mode

    xplct

      Causes records to be flushed only when the file is closed, or when an explicit flush is done

  deq=INTEGER

    Sets the default extension quantity

  dna=FILESPEC

    Sets the default filename string. Used to fill in any missing pieces of the filename passed.

  fop=STRING

    File processing option. Takes one or more of the following (in a comma-separated list if there's more than one)

    ctg

      Contiguous.

    cbt

      Contiguous-best-try.

    dfw

      Deferred write; only applicable to files opened for shared access.

    dlt

      Delete file on close.

    tef

      Truncate at end-of-file.

    cif

      Create if nonexistent.

    sup

      Supersede.

    scf

      Submit as command file on close.

    spl

      Spool to system printer on close.

    tmd

      Temporary delete.

    tmp

      Temporary (no file directory).

    nef

      Not end-of-file.

    rck

      Read check compare operation.

    wck

      Write check compare operation.

    mxv

      Maximize version number.

    rwo

      Rewind file on open.

    pos

      Current position.

    rwc

      Rewind file on close.

    sqo

      File can only be processed in a sequential manner.

  fsz=INTEGER

    Fixed header size

  gbc=INTEGER

    Global buffers requested for the file

  mbc=INTEGER

    Multiblock count

  mbf=INTEGER

    Bultibuffer count

  mrs=INTEGER

    Maximum record size

  rat=STRING

    File record attributes. Takes one of the following:

    cr

      Carriage-return control.

    blk

      Disallow records to span block boundaries.

    ftn

      FORTRAN print control.

    none

      Explicitly forces no carriage control.

    prn

      Print file format.

  rfm=STRING

    File record format. Takes one of the following:

    fix

      Fixed-length record format.

    stm

      RMS stream record format.

    stmlf

      Stream format with line-feed terminator.

    stmcr

      Stream format with carriage-return terminator.

    var

      Variable-length record format.

    vfc

      Variable-length record with fixed control.

    udf

      Undefined format

  rop=STRING

    Record processing operations. Takes one or more of the following in a comma-separated list:

    asy

      Asynchronous I/O.

    cco

      Cancel Ctrl/O (used with Terminal I/O).

    cvt

      Capitalizes characters on a read from the terminal.

    eof

      Positions the record stream to the end-of-file for the connect operation only.

    nlk

      Do not lock record.

    pmt

      Enables use of the prompt specified by pmt=usr-prmpt on input from the terminal.

    pta

      Eliminates any information in the type-ahead buffer on a read from the terminal.

    rea

      Locks record for a read operation for this process, while allowing other accessors to read the record.

    rlk

      Locks record for write.

    rne

      Suppresses echoing of input data on the screen as it is entered on the keyboard.

    rnf

      Indicates that Ctrl/U, Ctrl/R, and DELETE are not to be considered control commands on terminal input, but are to be passed to the application program.

    rrl

      Reads regardless of lock.

    syncsts

      Returns success status of RMS$_SYNCH if the requested service completes its task immediately.

    tmo

      Timeout I/O.

    tpt

      Allows put/write services using sequential record access mode to occur at any point in the file, truncating the file at that point.

    ulk

      Prohibits RMS from automatically unlocking records.

    wat

      Wait until record is available, if currently locked by another stream.

    rah

      Read ahead.

    wbh

      Write behind.

  rtv=INTEGER

    The number of retrieval pointers that RMS has to maintain (0 to 127255)

  shr=STRING

    File sharing options. Choose one of the following:

    del

      Allows users to delete.

    get

      Allows users to read.

    mse

      Allows mainstream access.

    nil

      Prohibits file sharing.

    put

      Allows users to write.

    upd

      Allows users to update.

    upi

      Allows one or more writers.

  tmo=INTEGER

    I/O timeout value

vmssysopen

  This function bears the same relationship to the CORE function `sysopen` as `vmsopen` does to `open`. Its first three arguments are the name, access flags, and permissions for the file. Like `vmsopen`, it takes up to 8 additional string arguments which specify file characteristics. Its return value is identical to that of `vmsopen`.

  The symbolic constants for the mode argument are exported by VMS::Stdio by default, and are also exported by the Fcntl package.

waitfh

  This function causes Perl to wait for the completion of an I/O operation on the file handle specified as its argument. It is used with handles opened for asynchronous I/O, and performs its task by calling the CRTL routine fwait().

writeof

  This function writes an EOF to a file handle, if the device driver supports this operation. Its primary use is to send an EOF to a subprocess through a pipe opened for writing without closing the pipe. It returns a true value if successful, and `undef` if it encounters an error.

# REVISION

This document was last revised on 13-Oct-1998, for Perl 5.004, 5.005, and 5.6.0.