VMS::Stdio

CONTENTS

• 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 was changed to from VMS::stdio to VMS::Stdio as of Perl 5.002, and the names of some routines were changed. For many releases, calls to the old VMS::stdio routines would generate a warning, and then route to the equivalent VMS::Stdio function. This compatibility interface has now been removed.

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, useing 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, undefd, 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.