X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/7949c6f5835be2397160861a571a7477a640bf42..4ed3fda49b8590b1f2536acfe87ecdec36a6d516:/pod/perlrun.pod diff --git a/pod/perlrun.pod b/pod/perlrun.pod index 246d5b3..c3b30c8 100644 --- a/pod/perlrun.pod +++ b/pod/perlrun.pod @@ -10,11 +10,10 @@ B S<[ B<-sTtuUWX> ]> S<[ B<-pna> ] [ B<-F>I ] [ B<-l>[I] ] [ B<-0>[I] ]> S<[ B<-I>I ] [ B<-m>[B<->]I ] [ B<-M>[B<->]I<'module...'> ] [ B<-f> ]> S<[ B<-C [I] >]> - S<[ B<-P> ]> S<[ B<-S> ]> S<[ B<-x>[I] ]> S<[ B<-i>[I] ]> - S<[ B<-eE> I<'command'> ] [ B<--> ] [ I ] [ I ]...> + S<[ [B<-e>|B<-E>] I<'command'> ] [ B<--> ] [ I ] [ I ]...> =head1 DESCRIPTION @@ -78,9 +77,10 @@ Parsing of the #! switches starts wherever "perl" is mentioned in the line. The sequences "-*" and "- " are specifically ignored so that you could, if you were so inclined, say - #!/bin/sh -- # -*- perl -*- -p - eval 'exec perl -wS $0 ${1+"$@"}' - if $running_under_some_shell; + #!/bin/sh + #! -*-perl-*- + eval 'exec perl -x -wS $0 ${1+"$@"}' + if 0; to let Perl see the B<-p> switch. @@ -280,7 +280,7 @@ An alternate delimiter may be specified using B<-F>. =item B<-C [I]> X<-C> -The C<-C> flag controls some Unicode of the Perl Unicode features. +The C<-C> flag controls some of the Perl Unicode features. As of 5.8.1, the C<-C> can be followed either by a number or a list of option letters. The letters, their numeric values, and effects @@ -342,6 +342,11 @@ that enabled the use of Unicode-aware "wide system call" Win32 APIs. This feature was practically unused, however, and the command line switch was therefore "recycled".) +B Since perl 5.10.0, the -C option can no longer be used +on the #! line. It wasn't working there anyway, since the standard streams +are already set up at this point in the execution of the perl interpreter. +You can use binmode() instead to get the desired behaviour. + =item B<-c> X<-c> @@ -395,8 +400,8 @@ B<-D14> is equivalent to B<-Dtls>): 8 t Trace execution 16 o Method and overloading resolution 32 c String/numeric conversions - 64 P Print profiling info, preprocessor command for -P, source file input state - 128 m Memory allocation + 64 P Print profiling info, source file input state + 128 m Memory and SV allocation 256 f Format processing 512 r Regular expression parsing and execution 1024 x Syntax tree dump @@ -405,7 +410,6 @@ B<-D14> is equivalent to B<-Dtls>): 8192 H Hash dump -- usurps values() 16384 X Scratchpad allocation 32768 D Cleaning up - 65536 S Thread synchronization 131072 T Tokenising 262144 R Include reference counts of dumped variables (eg when using -Ds) 524288 J Do not s,t,P-debug (Jump over) opcodes within package DB @@ -455,10 +459,10 @@ X<-f> Disable executing F<$Config{sitelib}/sitecustomize.pl> at startup. Perl can be built so that it by default will try to execute -F<$Config{sitelib}/sitecustomize.pl> at startup. This is a hook that -allows the sysadmin to customize how perl behaves. It can for -instance be used to add entries to the @INC array to make perl find -modules in non-standard locations. +F<$Config{sitelib}/sitecustomize.pl> at startup (in a BEGIN block). +This is a hook that allows the sysadmin to customize how perl behaves. +It can for instance be used to add entries to the @INC array to make perl +find modules in non-standard locations. =item B<-F>I X<-F> @@ -588,9 +592,7 @@ proceeds from STDIN to STDOUT as might be expected. X<-I> X<@INC> Directories specified by B<-I> are prepended to the search path for -modules (C<@INC>), and also tells the C preprocessor where to search for -include files. The C preprocessor is invoked with B<-P>; by default it -searches /usr/include and /usr/lib/perl. +modules (C<@INC>). =item B<-l>[I] X<-l> X<$/> X<$\> @@ -659,6 +661,10 @@ Note that the lines are not printed by default. See B<-p> to have lines printed. If a file named by an argument cannot be opened for some reason, Perl warns you about it and moves on to the next file. +Also note that C<< <> >> passes command line arguments to +L, which doesn't necessarily interpret them as file names. +See L for possible security implications. + Here is an efficient way to delete all files that haven't been modified for at least a week: @@ -695,72 +701,6 @@ overrides a B<-n> switch. C and C blocks may be used to capture control before or after the implicit loop, just as in B. -=item B<-P> -X<-P> - -B - -This option causes your program to be run through the C preprocessor before -compilation by Perl. Because both comments and B directives begin -with the # character, you should avoid starting comments with any words -recognized by the C preprocessor such as C<"if">, C<"else">, or C<"define">. - -If you're considering using C<-P>, you might also want to look at the -Filter::cpp module from CPAN. - -The problems of -P include, but are not limited to: - -=over 10 - -=item * - -The C<#!> line is stripped, so any switches there don't apply. - -=item * - -A C<-P> on a C<#!> line doesn't work. - -=item * - -B lines that begin with (whitespace and) a C<#> but -do not look like cpp commands, are stripped, including anything -inside Perl strings, regular expressions, and here-docs . - -=item * - -In some platforms the C preprocessor knows too much: it knows about -the C++ -style until-end-of-line comments starting with C<"//">. -This will cause problems with common Perl constructs like - - s/foo//; - -because after -P this will became illegal code - - s/foo - -The workaround is to use some other quoting separator than C<"/">, -like for example C<"!">: - - s!foo!!; - - - -=item * - -It requires not only a working C preprocessor but also a working -F. If not on UNIX, you are probably out of luck on this. - -=item * - -Script line numbers are not preserved. - -=item * - -The C<-x> does not work with C<-P>. - -=back - =item B<-s> X<-s> @@ -869,10 +809,6 @@ execute a portion of your program before dumping, use the dump() operator instead. Note: availability of B is platform specific and may not be available for a specific port of Perl. -This switch has been superseded in favor of the new Perl code -generator backends to the compiler. See L and L -for details. - =item B<-U> X<-U> @@ -967,12 +903,20 @@ See L. =item B<-x> X<-x> -=item B<-x> I +=item B<-x>I tells Perl that the program is embedded in a larger chunk of unrelated ASCII text, such as in a mail message. Leading garbage will be discarded until the first line that starts with #! and contains the string "perl". Any meaningful switches on that line will be applied. + +All references to line numbers by the program (warnings, errors, ...) +will treat the #! line as the first line. +Thus a warning on the 2nd line of the program (which is on the 100th +line in the file) will be reported as line 2, and not as line 100. +This can be overridden by using the #line directive. +(See L) + If a directory name is specified, Perl will switch to that directory before running the program. The B<-x> switch controls only the disposal of leading garbage. The program must be terminated with @@ -980,6 +924,9 @@ C<__END__> if there is trailing garbage to be ignored (the program can process any or all of the trailing garbage via the DATA filehandle if desired). +The directory, if specified, must appear immediately following the B<-x> +with no intervening whitespace. + =back =head1 ENVIRONMENT @@ -1027,7 +974,7 @@ is used. The program should instead say: X Command-line options (switches). Switches in this variable are taken -as if they were on every Perl command line. Only the B<-[CDIMUdmtwA]> +as if they were on every Perl command line. Only the B<-[CDIMUdmtwW]> switches are allowed. When running taint checks (because the program was running setuid or setgid, or the B<-T> switch was used), this variable is ignored. If PERL5OPT begins with B<-T>, tainting will be @@ -1124,9 +1071,9 @@ X<:utf8> A pseudolayer that turns on a flag on the layer below to tell perl that output should be in utf8 and that input should be regarded as -already in utf8 form. May be useful in PERLIO environment -variable to make UTF-8 the default. (To turn off that behaviour -use C<:bytes> layer.) +already in valid utf8 form. It does not check for validity and as such +should be handled with caution for input. Generally C<:encoding(utf8)> is +the best option when reading UTF-8 encoded data. =item :win32 X<:win32> @@ -1156,6 +1103,9 @@ compiler's numeric file descriptor routines. There is an experimental native C layer which is expected to be enhanced and should eventually be the default under Win32. +The PERLIO environment variable is completely ignored when perl +is run in taint mode. + =item PERLIO_DEBUG X @@ -1180,6 +1130,9 @@ A list of directories in which to look for Perl library files before looking in the standard library and the current directory. If PERL5LIB is defined, PERLLIB is not used. +The PERLLIB environment variable is completely ignored when perl +is run in taint mode. + =item PERL5DB X @@ -1187,6 +1140,9 @@ The command used to load the debugger code. The default is: BEGIN { require 'perl5db.pl' } +The PERL5DB environment variable only used when perl is started with +a bare B<-d> switch. + =item PERL5DB_THREADED X @@ -1209,6 +1165,11 @@ fit for interactive use, and setting COMSPEC to such a shell may interfere with the proper functioning of other programs (which usually look in COMSPEC to find a shell fit for interactive use). +Before Perl 5.10.0 and 5.8.8, PERL5SHELL was not taint checked +when running external commands. It is recommended that +you explicitly set (or delete) C<$ENV{PERL5SHELL}> when running +in taint mode under Windows. + =item PERL_ALLOW_NON_IFS_LSP (specific to the Win32 port) X @@ -1258,20 +1219,23 @@ PERL_ENCODING environment variable is consulted for an encoding name. =item PERL_HASH_SEED X -(Since Perl 5.8.1.) Used to randomise Perl's internal hash function. +(Since Perl 5.8.1.) Used to randomise perl's internal hash function. To emulate the pre-5.8.1 behaviour, set to an integer (zero means exactly the same order as 5.8.0). "Pre-5.8.1" means, among other -things, that hash keys will be ordered the same between different runs -of Perl. +things, that hash keys will always have the same ordering between +different runs of perl. + +Most hashes return elements in the same order as Perl 5.8.0 by default. +On a hash by hash basis, if pathological data is detected during a hash +key insertion, then that hash will switch to an alternative random hash +seed. The default behaviour is to randomise unless the PERL_HASH_SEED is set. -If Perl has been compiled with C<-DUSE_HASH_SEED_EXPLICIT>, the default +If perl has been compiled with C<-DUSE_HASH_SEED_EXPLICIT>, the default behaviour is B to randomise unless the PERL_HASH_SEED is set. -If PERL_HASH_SEED is unset or set to a non-numeric string, Perl uses +If PERL_HASH_SEED is unset or set to a non-numeric string, perl uses the pseudorandom seed supplied by the operating system and libraries. -This means that each different run of Perl will have a different -ordering of the results of keys(), values(), and each(). B. Hashes are randomized to protect against local and remote attacks against Perl