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NAMEperl - Practical Extraction and Report Language SYNOPSISFor ease of access, the Perl manual has been split up into a number of sections:
(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.) Additional documentation for perl modules is available in the F
.profile (for sh, bash or ksh users):
MANPATH=$MANPATH:/usr/local/lib/perl5/man
export MANPATH
.login (for csh or tcsh users):
setenv MANPATH $MANPATH:/usr/local/lib/perl5/man
If that doesn't work for some reason, you can still use the supplied perldoc script to view module information. 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. DESCRIPTIONPerl is an interpreted 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). It 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 hash tables used by 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 associative arrays (where dbm is available). 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. But wait, there's more... Perl version 5 is nearly a complete rewrite, and provides the following additional benefits:
Ok, that's definitely enough hype. ENVIRONMENT
Apart from these, Perl uses no other environment variables, except to make them available to the script being executed, and to child processes. However, scripts running setuid would do well to execute the following lines before doing anything else, just to keep people honest:
$ENV{'PATH'} = '/bin:/usr/bin'; # or whatever you need
$ENV{'SHELL'} = '/bin/sh' if defined $ENV{'SHELL'};
$ENV{'IFS'} = '' if defined $ENV{'IFS'};
AUTHORLarry Wall <F FILES
"/tmp/perl-e$$" temporary file for -e commands
"@INC" locations of perl 5 libraries
SEE ALSOa2p awk to perl translator s2p sed to perl translator DIAGNOSTICSThe -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? BUGSThe -w switch is not mandatory. Perl is at the mercy of your machine's definitions of various operations such as type casting, atof() and 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 identifier 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. Perl actually stands for Pathologically Eclectic Rubbish Lister, but don't tell anyone I said that. NOTESThe 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 principle virtues of a programmer are Laziness, Impatience, and Hubris. See the Camel Book for why.
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