=head1 SYNOPSIS
-B<perl> S<[ B<-sTuUWX> ]>
+B<perl> S<[ B<-sTtuUWX> ]>
S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]>
- S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]>
+ S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal/hexadecimal>] ]>
S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]>
S<[ B<-P> ]>
S<[ B<-S> ]>
S<[ B<-x>[I<dir>] ]>
S<[ B<-i>[I<extension>] ]>
S<[ B<-e> I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
+ S<[ B<-A [I<assertions>] >]>
+ S<[ B<-C [I<number/list>] >]>
=head1 DESCRIPTION
eval 'exec perl -wS $0 ${1+"$@"}'
if $running_under_some_shell;
-to let Perl see the B<-p> switch.
+to let Perl see the B<-p> switch.
A similar trick involves the B<env> program, if you have it.
=item Win95/NT
-The Win95/NT installation, when using the Activeware port of Perl,
+The Win95/NT installation, when using the ActiveState installer for Perl,
will modify the Registry to associate the F<.pl> extension with the perl
-interpreter. If you install another port of Perl, including the one
-in the Win32 directory of the Perl distribution, then you'll have to
-modify the Registry yourself. Note that this means you can no
-longer tell the difference between an executable Perl program
-and a Perl library file.
+interpreter. If you install Perl by other means (including building from
+the sources), you may have to modify the Registry yourself. Note that
+this means you can no longer tell the difference between an executable
+Perl program and a Perl library file.
=item Macintosh
one-liners (see B<-e> below).
On some systems, you may have to change single-quotes to double ones,
-which you must I<not> do on Unix or Plan9 systems. You might also
+which you must I<not> do on Unix or Plan 9 systems. You might also
have to change a single % to a %%.
For example:
=over 5
-=item B<-0>[I<digits>]
+=item B<-0>[I<octal/hexadecimal>]
-specifies the input record separator (C<$/>) as an octal number. If there are
-no digits, the null character is the separator. Other switches may
-precede or follow the digits. For example, if you have a version of
-B<find> which can print filenames terminated by the null character, you
-can say this:
+specifies the input record separator (C<$/>) as an octal or
+hexadecimal number. If there are no digits, the null character is the
+separator. Other switches may precede or follow the digits. For
+example, if you have a version of B<find> which can print filenames
+terminated by the null character, you can say this:
find . -name '*.orig' -print0 | perl -n0e unlink
The special value 00 will cause Perl to slurp files in paragraph mode.
The value 0777 will cause Perl to slurp files whole because there is no
-legal character with that value.
+legal byte with that value.
+
+If you want to specify any Unicode character, use the hexadecimal
+format: C<-0xHHH...>, where the C<H> are valid hexadecimal digits.
+(This means that you cannot use the C<-x> with a directory name that
+consists of hexadecimal digits.)
+
+=item B<-A [I<assertions>]>
+
+Activates the assertions given after the switch as a comma-separated
+list of assertion names. If no assertion name is given, activates all
+assertions. See L<assertions>.
=item B<-a>
An alternate delimiter may be specified using B<-F>.
+=item B<-C [I<number/list>]>
+
+The C<-C> flag controls some Unicode 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
+are as follows; listing the letters is equal to summing the numbers.
+
+ I 1 STDIN is assumed to be in UTF-8
+ O 2 STDOUT will be in UTF-8
+ E 4 STDERR will be in UTF-8
+ S 7 I + O + E
+ i 8 UTF-8 is the default PerlIO layer for input streams
+ o 16 UTF-8 is the default PerlIO layer for output streams
+ D 24 i + o
+ A 32 the @ARGV elements are expected to be strings encoded in UTF-8
+ L 64 normally the "IOEioA" are unconditional,
+ the L makes them conditional on the locale environment
+ variables (the LC_ALL, LC_TYPE, and LANG, in the order
+ of decreasing precedence) -- if the variables indicate
+ UTF-8, then the selected "IOEioA" are in effect
+
+For example, C<-COE> and C<-C6> will both turn on UTF-8-ness on both
+STDOUT and STDERR. Repeating letters is just redundant, not cumulative
+nor toggling.
+
+The C<io> options mean that any subsequent open() (or similar I/O
+operations) will have the C<:utf8> PerlIO layer implicitly applied
+to them, in other words, UTF-8 is expected from any input stream,
+and UTF-8 is produced to any output stream. This is just the default,
+with explicit layers in open() and with binmode() one can manipulate
+streams as usual.
+
+C<-C> on its own (not followed by any number or option list), or the
+empty string C<""> for the C<$ENV{PERL_UNICODE}, has the same effect
+as <-CSDL>. In other words, the standard I/O handles and the default
+C<open()> layer are UTF-8-fied B<but> only if the locale environment
+variables indicate a UTF-8 locale. This behaviour follows the
+I<implicit> (and problematic) UTF-8 behaviour of Perl 5.8.0.
+
+You can use C<-C0> (or C<"0"> for $ENV{PERL_UNICODE}) to explicitly
+disable all the above Unicode features.
+
+The read-only magic variable C<${^UNICODE}> reflects the numeric value
+of this setting. This is variable is set during Perl startup and is
+thereafter read-only. If you want runtime effects, use the three-arg
+open() (see L<perlfunc/open>), the two-arg binmode() (see L<perlfunc/binmode>),
+and the C<open> pragma (see L<open>).
+
+(In Perls earlier than 5.8.1 the C<-C> switch was a Win32-only switch
+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".)
+
=item B<-c>
causes Perl to check the syntax of the program and then exit without
runs the program under the Perl debugger. See L<perldebug>.
-=item B<-d:>I<foo>
+=item B<-d:>I<foo[=bar,baz]>
runs the program under the control of a debugging, profiling, or
tracing module installed as Devel::foo. E.g., B<-d:DProf> executes
-the program using the Devel::DProf profiler. See L<perldebug>.
+the program using the Devel::DProf profiler. As with the B<-M>
+flag, options may be passed to the Devel::foo package where they
+will be received and interpreted by the Devel::foo::import routine.
+The comma-separated list of options must follow a C<=> character.
+See L<perldebug>.
=item B<-D>I<letters>
sets debugging flags. To watch how it executes your program, use
B<-Dtls>. (This works only if debugging is compiled into your
Perl.) Another nice value is B<-Dx>, which lists your compiled
-syntax tree. And B<-Dr> displays compiled regular expressions. As an
-alternative, specify a number instead of list of letters (e.g., B<-D14> is
-equivalent to B<-Dtls>):
+syntax tree. And B<-Dr> displays compiled regular expressions;
+the format of the output is explained in L<perldebguts>.
+
+As an alternative, specify a number instead of list of letters (e.g.,
+B<-D14> is equivalent to B<-Dtls>):
1 p Tokenizing and parsing
2 s Stack snapshots
+ with v, displays all stacks
4 l Context (loop) stack processing
8 t Trace execution
16 o Method and overloading resolution
32 c String/numeric conversions
- 64 P Print preprocessor command for -P
+ 64 P Print profiling info, preprocessor command for -P, source file input state
128 m Memory allocation
256 f Format processing
512 r Regular expression parsing and execution
1024 x Syntax tree dump
2048 u Tainting checks
- 4096 L Memory leaks (needs -DLEAKTEST when compiling Perl)
+ 4096 (Obsolete, previously used for LEAKTEST)
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
+ 1048576 v Verbose: use in conjunction with other flags
+ 2097152 C Copy On Write
All these flags require B<-DDEBUGGING> when you compile the Perl
-executable. See the F<INSTALL> file in the Perl source distribution
+executable (but see L<Devel::Peek>, L<re> which may change this).
+See the F<INSTALL> file in the Perl source distribution
for how to do this. This flag is automatically set if you include B<-g>
option when C<Configure> asks you about optimizer/debugger flags.
If you're just trying to get a print out of each line of Perl code
as it executes, the way that C<sh -x> provides for shell scripts,
-you can't use Perl's B<-D> switch. Instead do this
+you can't use Perl's B<-D> switch. Instead do this
+
+ # If you have "env" utility
+ env=PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program
# Bourne shell syntax
$ PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program
As shown above, Perl creates the backup file whether or not any output
is actually changed. So this is just a fancy way to copy files:
- $ perl -p -i '/some/file/path/*' -e 1 file1 file2 file3...
+ $ perl -p -i'/some/file/path/*' -e 1 file1 file2 file3...
or
- $ perl -p -i '.orig' -e 1 file1 file2 file3...
+ $ perl -p -i'.orig' -e 1 file1 file2 file3...
You can use C<eof> without parentheses to locate the end of each input
file, in case you want to append to each file, or reset line numbering
with the next one (if it exists).
For a discussion of issues surrounding file permissions and B<-i>,
-see L<perlfaq5/Why does Perl let me delete read-only files? Why
-does -i clobber protected files? Isn't this a bug in Perl?>.
+see L<perlfaq5/Why does Perl let me delete read-only files? Why does -i clobber protected files? Isn't this a bug in Perl?>.
You cannot use B<-i> to create directories or to strip extensions from
files.
This is faster than using the B<-exec> switch of B<find> because you don't
have to start a process on every filename found. It does suffer from
the bug of mishandling newlines in pathnames, which you can fix if
-you
+you follow the example under B<-0>.
C<BEGIN> and C<END> blocks may be used to capture control before or after
the implicit program loop, just as in B<awk>.
=item B<-P>
-causes your program to be run through the C preprocessor before
-compilation by Perl. (Because both comments and B<cpp> directives begin
+B<NOTE: Use of -P is strongly discouraged because of its inherent
+problems, including poor portability.>
+
+This option causes your program to be run through the C preprocessor before
+compilation by Perl. Because both comments and B<cpp> directives begin
with the # character, you should avoid starting comments with any words
-recognized by the C preprocessor such as "if", "else", or "define".)
+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<All> 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<sed>. 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>
enables rudimentary switch parsing for switches on the command
line after the program name but before any filename arguments (or before
-a B<-->). Any switch found there is removed from @ARGV and sets the
+an argument of B<-->). This means you can have switches with two leading
+dashes (B<--help>). Any switch found there is removed from @ARGV and sets the
corresponding variable in the Perl program. The following program
-prints "true" if and only if the program is invoked with a B<-xyz> switch.
+prints "1" if the program is invoked with a B<-xyz> switch, and "abc"
+if it is invoked with B<-xyz=abc>.
#!/usr/bin/perl -s
- if ($xyz) { print "true\n" }
+ if ($xyz) { print "$xyz\n" }
+
+Do note that B<--help> creates the variable ${-help}, which is not compliant
+with C<strict refs>.
=item B<-S>
before being searched for on the PATH. On Unix platforms, the
program will be searched for strictly on the PATH.
+=item B<-t>
+
+Like B<-T>, but taint checks will issue warnings rather than fatal
+errors. These warnings can be controlled normally with C<no warnings
+qw(taint)>.
+
+B<NOTE: this is not a substitute for -T.> This is meant only to be
+used as a temporary development aid while securing legacy code:
+for real production code and for new secure code written from scratch
+always use the real B<-T>.
+
=item B<-T>
forces "taint" checks to be turned on so you can test them. Ordinarily
=item B<-V:>I<name>
Prints to STDOUT the value of the named configuration variable.
-For example,
+For example,
$ perl -V:man.dir
using an array as though it were a scalar, if your subroutines
recurse more than 100 deep, and innumerable other things.
-This switch really just enables the internal C<^$W> variable. You
+This switch really just enables the internal C<$^W> variable. You
can disable or promote into fatal errors specific warnings using
C<__WARN__> hooks, as described in L<perlvar> and L<perlfunc/warn>.
See also L<perldiag> and L<perltrap>. A new, fine-grained warning
facility is also available if you want to manipulate entire classes
-of warnings; see L<warnings> (or better yet, its source code) about
-that.
+of warnings; see L<warnings> or L<perllexwarn>.
=item B<-W>
-Enables all warnings regardless of
+Enables all warnings regardless of C<no warnings> or C<$^W>.
See L<perllexwarn>.
=item B<-X>
-Disables all warnings regardless of
+Disables all warnings regardless of C<use warnings> or C<$^W>.
See L<perllexwarn>.
=item B<-x> I<directory>
=item PERL5LIB
-A colon-separated list of directories in which to look for Perl library
+A list of directories in which to look for Perl library
files before looking in the standard library and the current
directory. Any architecture-specific directories under the specified
locations are automatically included if they exist. If PERL5LIB is not
-defined, PERLLIB is used.
+defined, PERLLIB is used. Directories are separated (like in PATH) by
+a colon on unixish platforms and by a semicolon on Windows (the proper
+path separator being given by the command C<perl -V:path_sep>).
When running taint checks (either because the program was running setuid
or setgid, or the B<-T> switch was used), neither variable is used.
=item PERL5OPT
Command-line options (switches). Switches in this variable are taken
-as if they were on every Perl command line. Only the B<-[DIMUdmw]>
+as if they were on every Perl command line. Only the B<-[DIMUdmtw]>
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
enabled, and any subsequent options ignored.
+=item PERLIO
+
+A space (or colon) separated list of PerlIO layers. If perl is built
+to use PerlIO system for IO (the default) these layers effect perl's IO.
+
+It is conventional to start layer names with a colon e.g. C<:perlio> to
+emphasise their similarity to variable "attributes". But the code that parses
+layer specification strings (which is also used to decode the PERLIO
+environment variable) treats the colon as a separator.
+
+An unset or empty PERLIO is equivalent to C<:stdio>.
+
+The list becomes the default for I<all> perl's IO. Consequently only built-in
+layers can appear in this list, as external layers (such as :encoding()) need
+IO in order to load them!. See L<"open pragma"|open> for how to add external
+encodings as defaults.
+
+The layers that it makes sense to include in the PERLIO environment
+variable are summarised below. For more details see L<PerlIO>.
+
+=over 8
+
+=item :bytes
+
+A pseudolayer that turns I<off> the C<:utf8> flag for the layer below.
+Unlikely to be useful on its own in the global PERLIO environment variable.
+You perhaps were thinking of C<:crlf:bytes> or C<:perlio:bytes>.
+
+=item :crlf
+
+A layer that implements DOS/Windows like CRLF line endings.
+On read converts pairs of CR,LF to a single "\n" newline character.
+On write converts each "\n" to a CR,LF pair.
+Based on the C<:perlio> layer.
+
+=item :mmap
+
+A layer which implements "reading" of files by using C<mmap()> to
+make (whole) file appear in the process's address space, and then
+using that as PerlIO's "buffer". This I<may> be faster in certain
+circumstances for large files, and may result in less physical memory
+use when multiple processes are reading the same file.
+
+Files which are not C<mmap()>-able revert to behaving like the C<:perlio>
+layer. Writes also behave like C<:perlio> layer as C<mmap()> for write
+needs extra house-keeping (to extend the file) which negates any advantage.
+
+The C<:mmap> layer will not exist if platform does not support C<mmap()>.
+
+=item :perlio
+
+A from scratch implementation of buffering for PerlIO. Provides fast
+access to the buffer for C<sv_gets> which implements perl's readline/E<lt>E<gt>
+and in general attempts to minimize data copying.
+
+C<:perlio> will insert a C<:unix> layer below itself to do low level IO.
+
+=item :pop
+
+An experimental pseudolayer that removes the topmost layer.
+Use with the same care as is reserved for nitroglyserin.
+
+=item :raw
+
+A pseudolayer that manipulates other layers. Applying the <:raw>
+layer is equivalent to calling C<binmode($fh)>. It makes the stream
+pass each byte as-is without any translation. In particular CRLF
+translation, and/or :utf8 intuited from locale are disabled.
+
+Arranges for all accesses go straight to the lowest buffered layer provided
+by the configration. That is it strips off any layers above that layer.
+
+In Perl 5.6 and some books the C<:raw> layer (previously sometimes also
+referred to as a "discipline") is documented as the inverse of the
+C<:crlf> layer. That is no longer the case - other layers which would
+alter binary nature of the stream are also disabled. If you want UNIX
+line endings on a platform that normally does CRLF translation, but still
+want UTF-8 or encoding defaults the appropriate thing to do is to add
+C<:perlio> to PERLIO environment variable.
+
+=item :stdio
+
+This layer provides PerlIO interface by wrapping system's ANSI C "stdio"
+library calls. The layer provides both buffering and IO.
+Note that C<:stdio> layer does I<not> do CRLF translation even if that
+is platforms normal behaviour. You will need a C<:crlf> layer above it
+to do that.
+
+=item :unix
+
+Lowest level layer which provides basic PerlIO operations in terms of
+UNIX/POSIX numeric file descriptor calls
+C<open(), read(), write(), lseek(), close()>
+
+=item :utf8
+
+A pseudolayer that turns on a flag on the layer below to tell perl
+that data sent to the stream should be converted to perl internal
+"utf8" form and that data from the stream should be considered as so
+encoded. On ASCII based platforms the encoding is UTF-8 and on EBCDIC
+platforms UTF-EBCDIC. May be useful in PERLIO environment variable to
+make UTF-8 the default. (To turn off that behaviour use C<:bytes>
+layer.)
+
+=item :win32
+
+On Win32 platforms this I<experimental> layer uses native "handle" IO
+rather than unix-like numeric file descriptor layer. Known to be
+buggy in this release.
+
+=back
+
+On all platforms the default set of layers should give acceptable results.
+
+For UNIX platforms that will equivalent of "unix perlio" or "stdio".
+Configure is setup to prefer "stdio" implementation if system's library
+provides for fast access to the buffer, otherwise it uses the "unix perlio"
+implementation.
+
+On Win32 the default in this release is "unix crlf". Win32's "stdio"
+has a number of bugs/mis-features for perl IO which are somewhat
+C compiler vendor/version dependent. Using our own C<crlf> layer as
+the buffer avoids those issues and makes things more uniform.
+The C<crlf> layer provides CRLF to/from "\n" conversion as well as
+buffering.
+
+This release uses C<unix> as the bottom layer on Win32 and so still uses C
+compiler's numeric file descriptor routines. There is an experimental native
+C<win32> layer which is expected to be enhanced and should eventually replace
+the C<unix> layer.
+
+=item PERLIO_DEBUG
+
+If set to the name of a file or device then certain operations of PerlIO
+sub-system will be logged to that file (opened as append). Typical uses
+are UNIX:
+
+ PERLIO_DEBUG=/dev/tty perl script ...
+
+and Win32 approximate equivalent:
+
+ set PERLIO_DEBUG=CON
+ perl script ...
+
+
=item PERLLIB
-A colon-separated list of directories in which to look for Perl library
+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.
=item PERL5SHELL (specific to the Win32 port)
May be set to an alternative shell that perl must use internally for
-executing "backtick" commands or system(). Default is C<cmd.exe /x/c>
+executing "backtick" commands or system(). Default is C<cmd.exe /x/d/c>
on WindowsNT and C<command.com /c> on Windows95. The value is considered
to be space-separated. Precede any character that needs to be protected
(like a space or backslash) with a backslash.
Relevant only if your perl executable was built with B<-DDEBUGGING>,
this controls the behavior of global destruction of objects and other
-references.
+references. See L<perlhack/PERL_DESTRUCT_LEVEL> for more information.
+
+=item PERL_ENCODING
+
+If using the C<encoding> pragma without an explicit encoding name, the
+PERL_ENCODING environment variable is consulted for an encoding name.
+
+=item PERL_HASH_SEED
+
+(Since Perl 5.8.1.) Used to randomise Perl's internal hash function.
+
+The default behaviour is B<not> to randomise if the PERL_HASH_SEED is
+unset. If Perl has been compiled with C<-DUSE_HASH_SEED>, the default
+behaviour B<is> to randomise. If Perl hash been compiled with
+C<-DNO_HASH_SEED>, the hash randomisation is completely disabled.
+
+If PERL_HASH_SEED is set to a numeric (positive integer) string,
+that is used as the seed.
+
+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.
+
+The seed being set means that each different run of Perl will have
+a different ordering of the results of keys(), values(), and each().
+
+See L<perlsec/"Algorithmic Complexity Attacks"> for more information.
+
+=item PERL_HASH_SEED_DEBUG
+
+(Since Perl 5.8.1.) Set to "1" to display (to STDERR) the value of
+the hash seed at the beginning of execution.
+
+=item PERL_ROOT (specific to the VMS port)
+
+A translation concealed rooted logical name that contains perl and the
+logical device for the @INC path on VMS only. Other logical names that
+affect perl on VMS include PERLSHR, PERL_ENV_TABLES, and
+SYS$TIMEZONE_DIFFERENTIAL but are optional and discussed further in
+L<perlvms> and in F<README.vms> in the Perl source distribution.
+
+=item PERL_SIGNALS
+
+In Perls 5.8.1 and later. If set to C<unsafe> the pre-Perl-5.8.0
+signals behaviour (immediate but unsafe) is restored. If set to
+C<safe> the safe (or deferred) signals are used.
+See L<perlipc/"Deferred Signals (Safe signals)">.
+
+=item PERL_UNICODE
+
+Equivalent to the B<-C> command-line switch. Note that this is not
+a boolean variable-- setting this to C<"1"> is not the right way to
+"enable Unicode" (whatever that would mean). You can use C<"0"> to
+"disable Unicode", though (or alternatively unset PERL_UNICODE in
+your shell before starting Perl). See the description of the C<-C>
+switch for more information.
+
+=item SYS$LOGIN (specific to the VMS port)
+
+Used if chdir has no argument and HOME and LOGDIR are not set.
=back
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