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Zlib(3) User Contributed Perl Documentation Zlib(3)

NAME

IO::Zlib - IO:: style interface to Compress::Zlib

SYNOPSIS

With any version of Perl 5 you can use the basic OO interface:

use IO::Zlib;

$fh = new IO::Zlib;

if ($fh->open("file.gz", "rb")) {

print <$fh>;

$fh->close;

}

$fh = IO::Zlib->new("file.gz", "wb9");

if (defined $fh) {

print $fh "bar\n";

$fh->close;

}

$fh = IO::Zlib->new("file.gz", "rb");

if (defined $fh) {

print <$fh>;

undef $fh; # automatically closes the file

} With Perl 5.004 you can also use the TIEHANDLE interface to access compressed files just like ordinary files:

use IO::Zlib;

tie *FILE, 'IO::Zlib', "file.gz", "wb";

print FILE "line 1\nline2\n";

tie *FILE, 'IO::Zlib', "file.gz", "rb";

while () { print "LINE: ", $ };

DESCRIPTION

"IO::Zlib" provides an IO:: style interface to Compress::Zlib and hence

to gzip/zlib compressed files. It provides many of the same methods as the IO::Handle interface.

Starting from IO::Zlib version 1.02, IO::Zlib can also use an external

gzip command. The default behaviour is to try to use an external gzip if no "Compress::Zlib" can be loaded, unless explicitly disabled by

use IO::Zlib qw(:gzipexternal 0);

If explicitly enabled by

use IO::Zlib qw(:gzipexternal 1);

then the external gzip is used iinnsstteeaadd of "Compress::Zlib". CCOONNSSTTRRUUCCTTOORR new ( [ARGS] )

Creates an "IO::Zlib" object. If it receives any parameters, they

are passed to the method "open"; if the open fails, the object is destroyed. Otherwise, it is returned to the caller. OOBBJJEECCTT MMEETTHHOODDSS

open ( FILENAME, MODE )

"open" takes two arguments. The first is the name of the file to open and the second is the open mode. The mode can be anything acceptable to Compress::Zlib and by extension anything acceptable to zlib (that basically means POSIX fopen() style mode strings plus an optional number to indicate the compression level). opened Returns true if the object currently refers to a opened file. close Close the file associated with the object and disassociate the file from the handle. Done automatically on destroy. getc Return the next character from the file, or undef if none remain. getline Return the next line from the file, or undef on end of string. Can

safely be called in an array context. Currently ignores $/

($INPUTRECORDSEPARATOR or $RS when English is in use) and treats

lines as delimited by "\n". getlines Get all remaining lines from the file. It will croak() if accidentally called in a scalar context. print ( ARGS... ) Print ARGS to the file. read ( BUF, NBYTES, [OFFSET] ) Read some bytes from the file. Returns the number of bytes

actually read, 0 on end-of-file, undef on error.

eof Returns true if the handle is currently positioned at end of file? seek ( OFFSET, WHENCE ) Seek to a given position in the stream. Not yet supported. tell Return the current position in the stream, as a numeric offset. Not yet supported. setpos ( POS ) Set the current position, using the opaque value returned by "getpos()". Not yet supported. getpos ( POS ) Return the current position in the string, as an opaque object. Not yet supported. UUSSIINNGG TTHHEE EEXXTTEERRNNAALL GGZZIIPP If the external gzip is used, the following "open"s are used:

open(FH, "gzip -dc $filename |") # for read opens

open(FH, " | gzip > $filename") # for write opens

You can modify the 'commands' for example to hardwire an absolute path by e.g.

use IO::Zlib ':gzipreadopen' => '/some/where/gunzip -c %s |';

use IO::Zlib ':gzipwriteopen' => '| /some/where/gzip.exe > %s';

The %s is expanded to be the filename ("sprintf" is used, so be careful

to escape any other "%" signs). The 'commands' are checked for sanity

- they must contain the %s, and the read open must end with the pipe

sign, and the write open must begin with the pipe sign. CCLLAASSSS MMEETTHHOODDSS hasCompressZlib Returns true if "Compress::Zlib" is available. Note that this does not mean that "Compress::Zlib" is being used: see "gzipexternal" and gzipused. gzipexternal Undef if an external gzip ccaann be used if "Compress::Zlib" is not available (see "hasCompressZlib"), true if an external gzip is explicitly used, false if an external gzip must not be used. See "gzipused". gzipused True if an external gzip is being used, false if not. gzipreadopen Return the 'command' being used for opening a file for reading using an external gzip. gzipwriteopen Return the 'command' being used for opening a file for writing using an external gzip. DIAGNOSTICS

IO::Zlib::getlines: must be called in list context

If you want read lines, you must read in list context.

IO::Zlib::gzopenexternal: mode '...' is illegal

Use only modes 'rb' or 'wb' or /wb[1-9]/.

IO::Zlib::import: '...' is illegal

The known import symbols are the ":gzipexternal", ":gzipreadopen", and ":gzipwriteopen". Anything else is not recognized.

IO::Zlib::import: ':gzipexternal' requires an argument

The ":gzipexternal" requires one boolean argument.

IO::Zlib::import: 'gzipreadopen' requires an argument

The ":gzipexternal" requires one string argument.

IO::Zlib::import: 'gzipread' '...' is illegal

The ":gzipreadopen" argument must end with the pipe sign (|) and

have the %s for the filename. See "USING THE EXTERNAL GZIP".

IO::Zlib::import: 'gzipwriteopen' requires an argument

The ":gzipexternal" requires one string argument.

IO::Zlib::import: 'gzipwriteopen' '...' is illegal

The ":gzipwriteopen" argument must begin with the pipe sign (|)

and have the %s for the filename. An output redirect (>) is also

often a good idea, depending on your operating system shell syntax. See "USING THE EXTERNAL GZIP".

IO::Zlib::import: no Compress::Zlib and no external gzip

Given that we failed to load "Compress::Zlib" and that the use of

an external gzip was disabled, IO::Zlib has not much chance of

working.

IO::Zlib::open: needs a filename

No filename, no open.

IO::Zlib::READ: NBYTES must be specified

We must know how much to read.

IO::Zlib::READ: OFFSET is not supported

Offsets of gzipped streams are not supported.

IO::Zlib::WRITE: too long LENGTH

The LENGTH must be less than or equal to the buffer size.

IO::Zlib::WRITE: OFFSET is not supported

Offsets of gzipped streams are not supported.