PERL(1) PERL(1)
NAME
perl - Practical Extraction and Report Language
SYNOPSIS
perl [ -sTuU ] [ -hv ] [ -V[:configvar] ]
[ -cw ] [ -d[:debugger] ] [ -D[number/list] ]
[ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal] ]
[ -Idir ] [ -m[-]module ] [ -M[-]'module...' ] [ -P ]
[ -S ] [ -x[dir] ] [ -i[extension] ]
[ -e 'command' ] [ -- ] [ programfile ] [ argument ]...
For ease of access, the Perl manual has been split up into a number of
sections:
perl Perl overview (this section)
perldelta Perl changes since previous version
perlfaq Perl frequently asked questions
perldata Perl data structures
perlsyn Perl syntax
perlop Perl operators and precedence
perlre Perl regular expressions
perlrun Perl execution and options
perlfunc Perl builtin functions
perlvar Perl predefined variables
perlsub Perl subroutines
perlmod Perl modules: how they work
perlmodlib Perl modules: how to write and use
perlform Perl formats
perllocale Perl locale support
perlref Perl references
perldsc Perl data structures intro
perllol Perl data structures: lists of lists
perltoot Perl OO tutorial
perlobj Perl objects
perltie Perl objects hidden behind simple variables
perlbot Perl OO tricks and examples
perlipc Perl interprocess communication
perldebug Perl debugging
perldiag Perl diagnostic messages
perlsec Perl security
perltrap Perl traps for the unwary
perlstyle Perl style guide
perlpod Perl plain old documentation
perlbook Perl book information
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perlembed Perl ways to embed perl in your C or C++ application
perlapio Perl internal IO abstraction interface
perlxs Perl XS application programming interface
perlxstut Perl XS tutorial
perlguts Perl internal functions for those doing extensions
perlcall Perl calling conventions from C
(If you're intending to read these straight through for the first time,
the suggested order will tend to reduce the number of forward
references.)
The above manpages are installed in the /usr/share/catman/u_man/cat1/
directory.
Extensive additional documentation for Perl modules is available. The
IRIX configuration of perl places the documentation for the standard
modules in the /usr/share/catman/p_man/cat3/perl5/ directory. The
documentation for third-party modules will by default be installed into
the /usr/catman/local/man3/perl5/ directory. These directories are all
in the standard IRIX MANPATH.
If something strange has gone wrong with your program and you're not sure
where you should look for help, try the -w switch first. It will often
point out exactly where the trouble is.
DESCRIPTION
Perl is a language optimized for scanning arbitrary text files,
extracting information from those text files, and printing reports based
on that information. It's also a good language for many system
management tasks. The language is intended to be practical (easy to use,
efficient, complete) rather than beautiful (tiny, elegant, minimal).
Perl combines (in the author's opinion, anyway) some of the best features
of C, sed, awk, and sh, so people familiar with those languages should
have little difficulty with it. (Language historians will also note some
vestiges of csh, Pascal, and even BASIC-PLUS.) Expression syntax
corresponds quite closely to C expression syntax. Unlike most Unix
utilities, Perl does not arbitrarily limit the size of your data--if
you've got the memory, Perl can slurp in your whole file as a single
string. Recursion is of unlimited depth. And the tables used by hashes
(previously called "associative arrays") grow as necessary to prevent
degraded performance. Perl uses sophisticated pattern matching
techniques to scan large amounts of data very quickly. Although
optimized for scanning text, Perl can also deal with binary data, and can
make dbm files look like hashes. Setuid Perl scripts are safer than C
programs through a dataflow tracing mechanism which prevents many stupid
security holes.
If you have a problem that would ordinarily use sed or awk or sh, but it
exceeds their capabilities or must run a little faster, and you don't
want to write the silly thing in C, then Perl may be for you. There are
also translators to turn your sed and awk scripts into Perl scripts.
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But wait, there's more...
Perl version 5 is nearly a complete rewrite, and provides the following
additional benefits:
⊕ Many usability enhancements
It is now possible to write much more readable Perl code (even
within regular expressions). Formerly cryptic variable names can be
replaced by mnemonic identifiers. Error messages are more
informative, and the optional warnings will catch many of the
mistakes a novice might make. This cannot be stressed enough.
Whenever you get mysterious behavior, try the -w switch!!! Whenever
you don't get mysterious behavior, try using -w anyway.
⊕ Simplified grammar
The new yacc grammar is one half the size of the old one. Many of
the arbitrary grammar rules have been regularized. The number of
reserved words has been cut by 2/3. Despite this, nearly all old
Perl scripts will continue to work unchanged.
⊕ Lexical scoping
Perl variables may now be declared within a lexical scope, like
"auto" variables in C. Not only is this more efficient, but it
contributes to better privacy for "programming in the large".
Anonymous subroutines exhibit deep binding of lexical variables
(closures).
⊕ Arbitrarily nested data structures
Any scalar value, including any array element, may now contain a
reference to any other variable or subroutine. You can easily
create anonymous variables and subroutines. Perl manages your
reference counts for you.
⊕ Modularity and reusability
The Perl library is now defined in terms of modules which can be
easily shared among various packages. A package may choose to
import all or a portion of a module's published interface. Pragmas
(that is, compiler directives) are defined and used by the same
mechanism.
⊕ Object-oriented programming
A package can function as a class. Dynamic multiple inheritance and
virtual methods are supported in a straightforward manner and with
very little new syntax. Filehandles may now be treated as objects.
⊕ Embeddable and Extensible
Perl may now be embedded easily in your C or C++ application, and
can either call or be called by your routines through a documented
interface. The XS preprocessor is provided to make it easy to glue
your C or C++ routines into Perl. Dynamic loading of modules is
supported, and Perl itself can be made into a dynamic library.
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⊕ POSIX compliant
A major new module is the POSIX module, which provides access to all
available POSIX routines and definitions, via object classes where
appropriate.
⊕ Package constructors and destructors
The new BEGIN and END blocks provide means to capture control as a
package is being compiled, and after the program exits. As a
degenerate case they work just like awk's BEGIN and END when you use
the -p or -n switches.
⊕ Multiple simultaneous DBM implementations
A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
files from the same script simultaneously. In fact, the old dbmopen
interface has been generalized to allow any variable to be tied to
an object class which defines its access methods.
⊕ Subroutine definitions may now be autoloaded
In fact, the AUTOLOAD mechanism also allows you to define any
arbitrary semantics for undefined subroutine calls. It's not for
just autoloading.
⊕ Regular expression enhancements
You can now specify nongreedy quantifiers. You can now do grouping
without creating a backreference. You can now write regular
expressions with embedded whitespace and comments for readability.
A consistent extensibility mechanism has been added that is upwardly
compatible with all old regular expressions.
⊕ Innumerable Unbundled Modules
The Comprehensive Perl Archive Network described in the perlmodlib
manpage contains hundreds of plug-and-play modules full of reusable
code. See http://www.perl.com/CPAN for a site near you.
⊕ Compilability
While not yet in full production mode, a working perl-to-C compiler
does exist. It can generate portable byte code, simple C, or
optimized C code.
Okay, that's definitely enough hype.
ENVIRONMENT
See the perlrun manpage.
AUTHOR
Larry Wall <larry@wall.org>, with the help of oodles of other folks.
If your Perl success stories and testimonials may be of help to others
who wish to advocate the use of Perl in their applications, or if you
wish to simply express your gratitude to Larry and the Perl developers,
please write to <perl-thanks@perl.org>.
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FILES
"/tmp/perl-e$$" temporary file for -e commands
"@INC" locations of perl libraries
SEE ALSO
a2p awk to perl translator
s2p sed to perl translator
DIAGNOSTICS
The -w switch produces some lovely diagnostics.
See the perldiag manpage for explanations of all Perl's diagnostics.
Compilation errors will tell you the line number of the error, with an
indication of the next token or token type that was to be examined. (In
the case of a script passed to Perl via -e switches, each -e is counted
as one line.)
Setuid scripts have additional constraints that can produce error
messages such as "Insecure dependency". See the perlsec manpage.
Did we mention that you should definitely consider using the -w switch?
IRIX SPECIFICS
Perl is compiled with a shared libperl.so, which lives in the /usr/lib32
directory. It is compiled with 5.003 compatibility on.
Perl's standard library installs into /usr/share/lib/perl5/, which may be
NFS mounted read-only. In that case, and if you wish to install modules
locally, you should consider moving the /usr/share/lib/perl5/site_perl/
directory to some place on the local disk, and create a symlink.
Perl is compiled -n32 -mips3. If you have any compiled modules from an
older IRIX release, they are probably compiled -32, and will have to be
recompiled before they will work. If your modules use libraries that are
not available in -n32, then you will need a version of perl compiled to
that ABI. You cannot link or load objects of different ABI. A version of
perl compiled -32 is available via SGI Freeware (CDROM or various Web
locations).
Perl is compiled to use drand48() as Perl's rand() function, instead of
the standard, weak PRNG.
BUGS
The -w switch is not mandatory.
Perl is at the mercy of your machine's definitions of various operations
such as type casting, atof(), and floating-point output with sprintf().
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If your stdio requires a seek or eof between reads and writes on a
particular stream, so does Perl. (This doesn't apply to sysread() and
syswrite().)
While none of the built-in data types have any arbitrary size limits
(apart from memory size), there are still a few arbitrary limits: a
given variable name may not be longer than 255 characters, and no
component of your PATH may be longer than 255 if you use -S. A regular
expression may not compile to more than 32767 bytes internally.
You may mail your bug reports (be sure to include full configuration
information as output by the myconfig program in the perl source tree, or
by perl -V) to <perlbug@perl.com>. If you've succeeded in compiling
perl, the perlbug script in the utils/ subdirectory can be used to help
mail in a bug report.
Perl actually stands for Pathologically Eclectic Rubbish Lister, but
don't tell anyone I said that.
NOTES
The Perl motto is "There's more than one way to do it." Divining how
many more is left as an exercise to the reader.
The three principal virtues of a programmer are Laziness, Impatience, and
Hubris. See the Camel Book for why.
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