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 ]...
If you're new to Perl, you should start with perlintro, which is a general intro for beginners and provides some background to help you navigate the rest of Perl's extensive documentation.
For ease of access, the Perl manual has been split up into several sections.
perl Perl overview (this section) perlintroPerl introduction for beginners perltocPerl documentation table of contentsperlreftutPerl references short introduction perldscPerl data structures intro perllolPerl data structures: arrays of arrays perlrequickPerl regular expressions quick start perlretutPerl regular expressions tutorial perlbootPerl OO tutorial for beginners perltootPerl OO tutorial, part 1 perltoocPerl OO tutorial, part 2 perlbotPerl OO tricks and examples perlstylePerl style guide perltrapPerl traps for the unwary perldebtutPerl debugging tutorial perlfaqPerl frequently asked questions perlfaq1General Questions About Perl perlfaq2Obtaining and Learning about Perl perlfaq3Programming Tools perlfaq4Data Manipulation perlfaq5Files and Formats perlfaq6Regexes perlfaq7Perl Language Issues perlfaq8System Interaction perlfaq9NetworkingperlsynPerl syntax perldataPerl data structures perlopPerl operators and precedence perlsubPerl subroutines perlfuncPerl built-in functions perlopentutPerl open() tutorial perlpacktut Perl pack() and unpack() tutorial perlpodPerl plain old documentation perlpodspec Perl plain old documentation format specification perlrunPerl execution and options perldiagPerl diagnostic messages perllexwarnPerl warnings and their control perldebugPerl debugging perlvarPerl predefined variables perlrePerl regular expressions, the rest of the story perlrefPerl references, the rest of the story perlformPerl formats perlobjPerl objects perltiePerl objects hidden behind simple variables perldbmfilterPerl DBM filters perlipcPerl interprocess communication perlforkPerl fork() information perlnumberPerl number semantics perlthrtutPerl threads tutorial perlothrtut Old Perl threads tutorial perlportPerl portability guide perllocalePerl locale support perluniintroPerl Unicode introduction perlunicodePerl Unicode support perlebcdicConsiderations for running Perl on EBCDIC platforms perlsecPerl security perlmodPerl modules: how they work perlmodlibPerl modules: how to write and use perlmodstylePerl modules: how to write modules with style perlmodinstallPerl modules: how to install from CPAN perlnewmodPerl modules: preparing a new module for distribution perlutilutilities packaged with the Perl distribution perlcompilePerl compiler suite intro perlfilterPerl source filtersperlembedPerl 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 perlapiPerl API listing (autogenerated) perlinternPerl internal functions (autogenerated) perliolC API for Perl's implementation of IO in Layers perlapioPerl internal IO abstraction interface perlhackPerl hackers guideperlbookPerl book information perltodoPerl things to do perlhistPerl history records perldeltaPerl changes since previous version perl572deltaPerl changes in version 5.7.2 perl571deltaPerl changes in version 5.7.1 perl570deltaPerl changes in version 5.7.0 perl561deltaPerl changes in version 5.6.1 perl56deltaPerl changes in version 5.6 perl5005deltaPerl changes in version 5.005 perl5004deltaPerl changes in version 5.004perlcnPerl for Simplified Chinese (in EUC-CN) perljpPerl for Japanese (in EUC-JP) perlkoPerl for Korean (in EUC-KR) perltwPerl for Traditional Chinese (in Big5)perlaixPerl notes for AIX perlamigaPerl notes for AmigaOS perlapolloPerl notes for Apollo DomainOS perlbeosPerl notes for BeOS perlbs2000Perl notes for POSIX-BC BS2000 perlcePerl notes for WinCE perlcygwinPerl notes for Cygwin perldguxPerl notes for DG/UX perldosPerl notes for DOS perlepocPerl notes for EPOC perlfreebsdPerl notes for FreeBSD perlhpuxPerl notes for HP-UX perlhurdPerl notes for Hurd perlirixPerl notes for Irix perlmachtenPerl notes for Power MachTen perlmacosPerl notes for Mac OS (Classic) perlmintPerl notes for MiNT perlmpeixPerl notes for MPE/iX perlnetwarePerl notes for NetWare perlos2Perl notes for OS/2 perlos390Perl notes for OS/390 perlplan9Perl notes for Plan 9 perlqnxPerl notes for QNX perlsolaris Perl notes for Solaris perltru64Perl notes for Tru64 perluts Perl notes for UTS perlvmesaPerl notes for VM/ESA perlvmsPerl notes for VMS perlvosPerl notes for Stratus VOS perlwin32Perl notes for WindowsBy 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
Described in perlobj, perlboot, perltoot, perltooc, and perlbot.
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 perldebtut, perldebug and perldebguts.
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.cpan.org/ the Comprehensive Perl Archive http://www.perl.org/ Perl Mongers (Perl user groups)The 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.