perl (manpage)
computing: software: documentation: manpages: perlm
Manpage
NAME
perl - Practical Extraction and Report Language
SYNOPSIS
- REDIRECT Template:arg/opt
- REDIRECT Template:fmt/arg/opt [ <-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> ]...
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 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.
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.
Overview
| perl (CPAN) | Perl overview (this section) |
| perlintro (CPAN) | Perl introduction for beginners |
| perltoc (CPAN) | Perl documentation table of contents |
Tutorials
| perlreftut (CPAN) | Perl references short introduction | ||||||||||||||||||
| perldsc (CPAN) | Perl data structures intro | ||||||||||||||||||
| perllol (CPAN) | Perl data structures: arrays of arrays | ||||||||||||||||||
| perlrequick (CPAN) | Perl regular expressions quick start | ||||||||||||||||||
| perlretut (CPAN) | Perl regular expressions tutorial | ||||||||||||||||||
| perlboot (CPAN) | Perl OO tutorial for beginners | ||||||||||||||||||
| perltoot (CPAN) | Perl OO tutorial, part 1 | ||||||||||||||||||
| perltooc (CPAN) | Perl OO tutorial, part 2 | ||||||||||||||||||
| perlbot (CPAN) | Perl OO tricks and examples | ||||||||||||||||||
| perlstyle (CPAN) | Perl style guide | ||||||||||||||||||
| perlcheat (CPAN) | Perl cheat sheet | ||||||||||||||||||
| perltrap (CPAN) | Perl traps for the unwary | ||||||||||||||||||
| perldebtut (CPAN) | Perl debugging tutorial | ||||||||||||||||||
| perlfaq (CPAN) | Perl frequently asked questions | ||||||||||||||||||
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Reference Manual
| perlsyn (CPAN) | Perl syntax | ||||
| perldata (CPAN) | Perl data structures | ||||
| perlop (CPAN) | Perl operators and precedence | ||||
| perlsub (CPAN) | Perl subroutines | ||||
| perlfunc (CPAN) | Perl built-in functions | ||||
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| perlpod (CPAN) | Perl plain old documentation | ||||
| perlpodspec (CPAN) | Perl plain old documentation format specification | ||||
| perlrun (CPAN) | Perl execution and options | ||||
| perldiag (CPAN) | Perl diagnostic messages | ||||
| perllexwarn (CPAN) | Perl warnings and their control | ||||
| perldebug (CPAN) | Perl debugging | ||||
| perlvar (CPAN) | Perl predefined variables | ||||
| perlre (CPAN) | Perl regular expressions, the rest of the story | ||||
| perlreref (CPAN) | Perl regular expressions quick reference | ||||
| perlref (CPAN) | Perl references, the rest of the story | ||||
| perlform (CPAN) | Perl formats | ||||
| perlobj (CPAN) | Perl objects | ||||
| perltie (CPAN) | Perl objects hidden behind simple variables | ||||
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| perlipc (CPAN) | Perl interprocess communication | ||||
| perlfork (CPAN) | Perl fork() information | ||||
| perlnumber (CPAN) | Perl number semantics | ||||
| perlthrtut (CPAN) | Perl threads tutorial | ||||
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| perlport (CPAN) | Perl portability guide | ||||
| perllocale (CPAN) | Perl locale support | ||||
| perluniintro (CPAN) | Perl Unicode introduction | ||||
| perlunicode (CPAN) | Perl Unicode support | ||||
| perlebcdic (CPAN) | Considerations for running Perl on EBCDIC platforms | ||||
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| perlsec (CPAN) | Perl security | ||||
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| perlmod (CPAN) | Perl modules: how they work | ||||
| perlmodlib (CPAN) | Perl modules: how to write and use | ||||
| perlmodstyle (CPAN) | Perl modules: how to write modules with style | ||||
| perlmodinstall (CPAN) | Perl modules: how to install from CPAN | ||||
| perlnewmod (CPAN) | Perl modules: preparing a new module for distribution | ||||
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| perlutil (CPAN) | utilities packaged with the Perl distribution | ||||
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| perlcompile (CPAN) | Perl compiler suite intro | ||||
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| perlfilter (CPAN) | Perl source filters | ||||
Internals and C Language Interface
| perlembed (CPAN) | Perl ways to embed perl in your C or C++ application |
| perldebguts (CPAN) | Perl debugging guts and tips |
| perlxstut (CPAN) | Perl XS tutorial |
| perlxs (CPAN) | Perl XS application programming interface |
| perlclib (CPAN) | Internal replacements for standard C library functions |
| perlguts (CPAN) | Perl internal functions for those doing extensions |
| perlcall (CPAN) | Perl calling conventions from C |
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| perlapi (CPAN) | Perl API listing (autogenerated) |
| perlintern (CPAN) | Perl internal functions (autogenerated) |
| perliol (CPAN) | C API for Perl's implementation of IO in Layers |
| perlapio (CPAN) | Perl internal IO abstraction interface |
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| perlhack (CPAN) | Perl hackers guide |
Miscellaneous
| perlbook (CPAN) | Perl book information |
| perltodo (CPAN) | Perl things to do |
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| perldoc (CPAN) | Look up Perl documentation in Pod format |
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| perlhist (CPAN) | Perl history records |
| perldelta (CPAN) | Perl changes since previous version |
| perl587delta (CPAN) | Perl changes in version 5.8.7 |
| perl586delta (CPAN) | Perl changes in version 5.8.6 |
| perl585delta (CPAN) | Perl changes in version 5.8.5 |
| perl584delta (CPAN) | Perl changes in version 5.8.4 |
| perl583delta (CPAN) | Perl changes in version 5.8.3 |
| perl582delta (CPAN) | Perl changes in version 5.8.2 |
| perl581delta (CPAN) | Perl changes in version 5.8.1 |
| perl58delta (CPAN) | Perl changes in version 5.8.0 |
| perl573delta (CPAN) | Perl changes in version 5.7.3 |
| perl572delta (CPAN) | Perl changes in version 5.7.2 |
| perl571delta (CPAN) | Perl changes in version 5.7.1 |
| perl570delta (CPAN) | Perl changes in version 5.7.0 |
| perl561delta (CPAN) | Perl changes in version 5.6.1 |
| perl56delta (CPAN) | Perl changes in version 5.6 |
| perl5005delta (CPAN) | Perl changes in version 5.005 |
| perl5004delta (CPAN) | Perl changes in version 5.004 |
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| perlartistic (CPAN) | Perl Artistic License |
| perlgpl (CPAN) | GNU General Public License |
Language-Specific
| perlcn (CPAN) | Perl for Simplified Chinese (in EUC-CN) |
| perljp (CPAN) | Perl for Japanese (in EUC-JP) |
| perlko (CPAN) | Perl for Korean (in EUC-KR) |
| perltw (CPAN) | Perl for Traditional Chinese (in Big5) |
Platform-Specific
| perlaix (CPAN) | Perl notes for AIX |
| perlamiga (CPAN) | Perl notes for AmigaOS |
| perlapollo (CPAN) | Perl notes for Apollo DomainOS |
| perlbeos (CPAN) | Perl notes for BeOS |
| perlbs2000 (CPAN) | Perl notes for POSIX-BC BS2000 |
| perlce (CPAN) | Perl notes for WinCE |
| perlcygwin (CPAN) | Perl notes for Cygwin |
| perldgux (CPAN) | Perl notes for DG/UX |
| perldos (CPAN) | Perl notes for DOS |
| perlepoc (CPAN) | Perl notes for EPOC |
| perlfreebsd (CPAN) | Perl notes for FreeBSD |
| perlhpux (CPAN) | Perl notes for HP-UX |
| perlhurd (CPAN) | Perl notes for Hurd |
| perlirix (CPAN) | Perl notes for Irix |
| perlmachten (CPAN) | Perl notes for Power MachTen |
| perlmacos (CPAN) | Perl notes for Mac OS (Classic) |
| perlmacosx (CPAN) | Perl notes for Mac OS X |
| perlmint (CPAN) | Perl notes for MiNT |
| perlmpeix (CPAN) | Perl notes for MPE/iX |
| perlnetware (CPAN) | Perl notes for NetWare |
| perlos2 (CPAN) | Perl notes for OS/2 |
| perlos390 (CPAN) | Perl notes for OS/390 |
| perlos400 (CPAN) | Perl notes for OS/400 |
| perlplan9 (CPAN) | Perl notes for Plan 9 |
| perlqnx (CPAN) | Perl notes for QNX |
| perlsolaris (CPAN) | Perl notes for Solaris |
| perltru64 (CPAN) | Perl notes for Tru64 |
| perluts (CPAN) | Perl notes for UTS |
| perlvmesa (CPAN) | Perl notes for VM/ESA |
| perlvms (CPAN) | Perl notes for VMS |
| perlvos (CPAN) | Perl notes for Stratus VOS |
| perlwin32 (CPAN) | Perl notes for Windows |
On Debian systems, you need to install the perl-doc package which contains the majority of the standard Perl documentation and the perldoc program.
Extensive additional documentation for Perl modules is available, both those distributed with Perl and third-party modules which are packaged or locally installed.
You should be able to view Perl's documentation with your man(1) program or perldoc(1).
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.
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
- 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
- support for light-weight processes (threads)
- Described in perlthrtut and threads.
- support for Unicode, internationalization, and localization
- Described in perluniintro, perllocale and Locale::Maketext.
- 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.
AVAILABILITY
Perl is available for most operating systems, including virtually all Unix-like platforms. See "Supported Platforms" in perlport for a listing.
ENVIRONMENT
See perlrun.
AUTHOR
Larry Wall larryspam@spamwallspam.spamorg, 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-thanksspam@spamperlspam.spamorg.
FILES
- "@INC"
- locations of perl libraries
SEE ALSO
- a2p: 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)
DIAGNOSTICS
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?
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().
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 perlbugspam@spamperlspam.spamorg. 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.