perl - Practical Extraction and Report Language
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 several sections:
perl Perl overview (this section) perlfaqPerl frequently asked questions perltocPerl documentation table of contents perlbookPerl book information perlsynPerl syntax perldataPerl data structures perlopPerl operators and precedence perlsubPerl subroutines perlfuncPerl builtin functions perlreftutPerl references short introduction perldscPerl data structures intro perlrequickPerl regular expressions quick start perlpodPerl plain old documentation perlstylePerl style guide perltrapPerl traps for the unwary perlrunPerl execution and options perldiagPerl diagnostic messages perllexwarnPerl warnings and their control perldebtutPerl debugging tutorial perldebugPerl debugging perlvarPerl predefined variables perllolPerl data structures: arrays of arrays perlopentutPerl open() tutorial perlretutPerl regular expressions tutorial perlrePerl regular expressions, the rest of the story perlrefPerl references, the rest of the story perlformPerl formats perlbootPerl OO tutorial for beginners perltootPerl OO tutorial, part 1 perltootcPerl OO tutorial, part 2 perlobjPerl objects perlbotPerl OO tricks and examples perltiePerl objects hidden behind simple variables perlipcPerl interprocess communication perlforkPerl fork() information perlnumberPerl number semantics perlthrtutPerl threads tutorial perlportPerl portability guide perllocalePerl locale support perlunicodePerl unicode support perlebcdicConsiderations for running Perl on EBCDIC platforms perlsecPerl security perlmodPerl modules: how they work perlmodlibPerl modules: how to write and use perlmodinstallPerl modules: how to install from CPAN perlnewmodPerl modules: preparing a new module for distribution perlfaq1General Questions About Perl perlfaq2Obtaining and Learning about Perl perlfaq3Programming Tools perlfaq4Data Manipulation perlfaq5Files and Formats perlfaq6Regexes perlfaq7Perl Language Issues perlfaq8System Interaction perlfaq9Networking perlcompilePerl compiler suite intro perlembedPerl ways to embed perl in your C or C++ application perldebgutsPerl debugging guts and tips perlxstutPerl XS tutorial perlxsPerl XS application programming interface perlclibInternal replacements for standard C library functions perlgutsPerl internal functions for those doing extensions perlcallPerl calling conventions from C perlutilutilities packaged with the Perl distribution perlfilterPerl source filters perldbmfilterPerl DBM filters perlapiPerl API listing (autogenerated) perlinternPerl internal functions (autogenerated) perlapioPerl internal IO abstraction interface perltodoPerl things to do perlhackPerl hackers guide perlhistPerl history records perldeltaPerl changes since previous version perl5005deltaPerl changes in version 5.005 perl5004deltaPerl changes in version 5.004 perlaixPerl notes for AIX perlamigaPerl notes for Amiga perlbs2000Perl notes for POSIX-BC BS2000 perlcygwinPerl notes for Cygwin perldosPerl notes for DOS perlepocPerl notes for EPOC perlhpuxPerl notes for HP-UX perlmachtenPerl notes for Power MachTen perlmacosPerl notes for Mac OS (Classic) perlmpeixPerl notes for MPE/iX perlos2Perl notes for OS/2 perlos390Perl notes for OS/390 perlsolaris Perl notes for Solaris perlvmesaPerl notes for VM/ESA perlvmsPerl notes for VMS perlvosPerl notes for Stratus VOS perlwin32Perl notes for Windows(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.)
By default, the manpages listed above are installed in the /usr/local/man/ directory.
Extensive additional documentation for Perl modules is available. The default configuration for perl will place this additional documentation in the /usr/local/lib/perl5/man directory (or else in the man subdirectory of the Perl library directory). Some of this additional documentation is distributed standard with Perl, but you'll also find documentation for third-party modules there.
You should be able to view Perl's documentation with your man(1) program by including the proper directories in the appropriate start-up files, or in the MANPATH environment variable. To find out where the configuration has installed the manpages, type:
perl -V:man.dirIf the directories have a common stem, such as /usr/local/man/man1 and /usr/local/man/man3, you need only to add that stem (/usr/local/man) to your man(1) configuration files or your MANPATH environment variable. If they do not share a stem, you'll have to add both stems.
If that doesn't work for some reason, you can still use the supplied perldoc script to view module information. You might also look into getting a replacement man program.
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.
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 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 (sometimes called "associative arrays") grow as necessary to prevent degraded performance. Perl can use sophisticated pattern matching techniques to scan large amounts of data 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 that 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.
But wait, there's more...
Begun in 1993 (see perlhist), Perl version 5 is nearly a complete rewrite that provides the following additional benefits:
modularity and reusability using innumerable modules
Described in perlmod, perlmodlib, and perlmodinstall.
embeddable and extensible
Described in perlembed, perlxstut, perlxs, perlcall, perlguts, and xsubpp.
roll-your-own magic variables (including multiple simultaneous DBM implementations)
Described in perltie and AnyDBM_File.
subroutines can now be overridden, autoloaded, and prototyped
Described in perlsub.
arbitrarily nested data structures and anonymous functions
Described in perlreftut, perlref, perldsc, and perllol.
object-oriented programming
compilability into C code or Perl bytecode
Described in B and B::Bytecode.
support for light-weight processes (threads)
Described in perlthrtut and Thread.
support for internationalization, localization, and Unicode
Described in perllocale and utf8.
lexical scoping
Described in perlsub.
regular expression enhancements
enhanced debugger and interactive Perl environment, with integrated editor support
Described in perldebug.
POSIX 1003.1 compliant library
Described in POSIX.
Okay, that's definitely enough hype.
Perl is available for most operating systems, including virtually all Unix-like platforms. See "Supported Platforms" in perlport for a listing.
See perlrun.
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 .
"@INC" locations of perl librariesa2p awk to perl translator s2p sed to perl translator http://www.perl.com/ the Perl Home Page http://www.perl.com/CPAN the Comprehensive Perl ArchiveThe use warnings pragma (and the -w switch) produces some lovely diagnostics.
See perldiag for explanations of all Perl's diagnostics. The use diagnostics pragma automatically turns Perl's normally terse warnings and errors into these longer forms.
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 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 perlsec.
Did we mention that you should definitely consider using the -w switch?
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().
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 251 characters. Line numbers displayed by diagnostics are internally stored as short integers, so they are limited to a maximum of 65535 (higher numbers usually being affected by wraparound).
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.org . 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.
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.