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<-cw> ] [ B<-d>[B<t>][:I<debugger>] ] [ B<-D>[I<number/list>] ]>
+ 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<-C [I<number/list>] >]> ]>
+ S<[ B<-A [I<assertions>] >]>
+ S<[ B<-C [I<number/list>] >]>
=head1 DESCRIPTION
=item MS-DOS
Create a batch file to run your program, and codify it in
-C<ALTERNATIVE_SHEBANG> (see the F<dosish.h> file in the source
+C<ALTERNATE_SHEBANG> (see the F<dosish.h> file in the source
distribution for more information).
=item Win95/NT
=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>
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
+ 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
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.
+empty string C<""> for the C<PERL_UNICODE> environment variable, has the
+same effect as C<-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 $ENV{PERL_UNICODE} ) to explicitly
+You can use C<-C0> (or C<"0"> for C<PERL_UNICODE>) to explicitly
disable all the above Unicode features.
-See L<perlfunc/open>, and L<open> for more information.
-
The read-only magic variable C<${^UNICODE}> reflects the numeric value
-of this setting, see L<perlvar/"${^UNICODE}">.
+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.
=item B<-d>
+=item B<-dt>
+
runs the program under the Perl debugger. See L<perldebug>.
+If B<t> is specified, it indicates to the debugger that threads
+will be used in the code being debugged.
=item B<-d:>I<foo[=bar,baz]>
+=item B<-dt:>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. 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.
+If B<t> is specified, it indicates to the debugger that threads
+will be used in the code being debugged.
See L<perldebug>.
=item B<-D>I<letters>
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
+ 1 p Tokenizing and parsing (with v, displays parse stack)
+ 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
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
+ 4194304 A Consistency checks on internal structures
+ 8388608 q quiet - currently only suppresses the "EXECUTING" message
All these flags require B<-DDEBUGGING> when you compile the Perl
executable (but see L<Devel::Peek>, L<re> which may change this).
This allows you to add a prefix to the backup file, instead of (or in
addition to) a suffix:
- $ perl -pi 'orig_*' -e 's/bar/baz/' fileA # backup to 'orig_fileA'
+ $ perl -pi'orig_*' -e 's/bar/baz/' fileA # backup to 'orig_fileA'
Or even to place backup copies of the original files into another
directory (provided the directory already exists):
- $ perl -pi 'old/*.orig' -e 's/bar/baz/' fileA # backup to 'old/fileA.orig'
+ $ perl -pi'old/*.orig' -e 's/bar/baz/' fileA # backup to 'old/fileA.orig'
These sets of one-liners are equivalent:
$ perl -pi -e 's/bar/baz/' fileA # overwrite current file
- $ perl -pi '*' -e 's/bar/baz/' fileA # overwrite current file
+ $ perl -pi'*' -e 's/bar/baz/' fileA # overwrite current file
- $ perl -pi '.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig'
- $ perl -pi '*.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig'
+ $ perl -pi'.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig'
+ $ perl -pi'*.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig'
From the shell, saying
$ perl -pi~ -e 's/foo/bar/' file1 file2 file3...
+Note that because B<-i> renames or deletes the original file before
+creating a new file of the same name, UNIX-style soft and hard links will
+not be preserved.
+
Finally, the B<-i> switch does not impede execution when no
files are given on the command line. In this case, no backup is made
(the original file cannot, of course, be determined) and processing
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.
-Here is an efficient way to delete all files older than a week:
+Here is an efficient way to delete all files that haven't been modified for
+at least a week:
find . -mtime +7 -print | perl -nle unlink
if ($xyz) { print "$xyz\n" }
Do note that B<--help> creates the variable ${-help}, which is not compliant
-with C<strict refs>.
+with C<strict refs>. Also, when using this option on a script with
+warnings enabled you may get a lot of spurious "used only once" warnings.
=item B<-S>
of those suffixes. If your Perl was compiled with DEBUGGING turned
on, using the -Dp switch to Perl shows how the search progresses.
-Typically this is used to emulate #! startup on platforms that
-don't support #!. This example works on many platforms that
-have a shell compatible with Bourne shell:
+Typically this is used to emulate #! startup on platforms that don't
+support #!. Its also convenient when debugging a script that uses #!,
+and is thus normally found by the shell's $PATH search mechanism.
+
+This example works on many platforms that have a shell compatible with
+Bourne shell:
#!/usr/bin/perl
eval 'exec /usr/bin/perl -wS $0 ${1+"$@"}'
prints summary of the major perl configuration values and the current
values of @INC.
-=item B<-V:>I<name>
+=item B<-V:>I<configvar>
+
+Prints to STDOUT the value of the named configuration variable(s),
+with multiples when your configvar argument looks like a regex (has
+non-letters). For example:
-Prints to STDOUT the value of the named configuration variable.
-For example,
+ $ perl -V:libc
+ libc='/lib/libc-2.2.4.so';
+ $ perl -V:lib.
+ libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc';
+ libc='/lib/libc-2.2.4.so';
+ $ perl -V:lib.*
+ libpth='/usr/local/lib /lib /usr/lib';
+ libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc';
+ lib_ext='.a';
+ libc='/lib/libc-2.2.4.so';
+ libperl='libperl.a';
+ ....
- $ perl -V:man.dir
+Additionally, extra colons can be used to control formatting. A
+trailing colon suppresses the linefeed and terminator ';', allowing
+you to embed queries into shell commands. (mnemonic: PATH separator
+':'.)
-will provide strong clues about what your MANPATH variable should
-be set to in order to access the Perl documentation.
+ $ echo "compression-vars: " `perl -V:z.*: ` " are here !"
+ compression-vars: zcat='' zip='zip' are here !
+
+A leading colon removes the 'name=' part of the response, this allows
+you to map to the name you need. (mnemonic: empty label)
+
+ $ echo "goodvfork="`./perl -Ilib -V::usevfork`
+ goodvfork=false;
+
+Leading and trailing colons can be used together if you need
+positional parameter values without the names. Note that in the case
+below, the PERL_API params are returned in alphabetical order.
+
+ $ echo building_on `perl -V::osname: -V::PERL_API_.*:` now
+ building_on 'linux' '5' '1' '9' now
=item B<-w>
Disables all warnings regardless of C<use warnings> or C<$^W>.
See L<perllexwarn>.
+=item B<-x>
+
=item B<-x> I<directory>
tells Perl that the program is embedded in a larger chunk of unrelated
=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.
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>.
+variable are
briefly summarised below. For more details see L<PerlIO>.
=over 8
=item :bytes
-Turns I<off> the C<:utf8> flag for the layer below.
-Unlikely to be useful in global PERLIO environment variable.
+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.
+A layer which does CRLF to "\n" translation distinguishing "text" and
+"binary" files in the manner of MS-DOS and similar operating systems.
+(It currently does I<not> mimic MS-DOS as far as treating of Control-Z
+as being an end-of-file marker.)
=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()>.
+using that as PerlIO's "buffer".
=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.
+This is a re-implementation of "stdio-like" buffering written as a
+PerlIO "layer". As such it will call whatever layer is below it for
+its operations (typically C<:unix>).
-C<:perlio> will insert a C<:unix> layer below itself to do low level IO.
+=item :pop
-=item :raw
+An experimental pseudolayer that removes the topmost layer.
+Use with the same care as is reserved for nitroglycerin.
-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 inuited from locale
-are disabled.
+=item :raw
-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.
+A pseudolayer that manipulates other layers. Applying the C<: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.
-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.
+Unlike in the earlier versions of Perl C<:raw> is I<not>
+just the inverse of C<:crlf> - other layers which would affect the
+binary nature of the stream are also removed or disabled.
=item :stdio
=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()>
+Low level layer which calls C<read>, C<write> and C<lseek> etc.
=item :utf8
-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.)
+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.)
=item :win32
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.
+C<win32> layer which is expected to be enhanced and should eventually be
+the default under Win32.
=item PERLIO_DEBUG
=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.
BEGIN { require 'perl5db.pl' }
+=item PERL5DB_THREADED
+
+If set to a true value, indicates to the debugger that the code being
+debugged uses threads.
+
=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.
interfere with the proper functioning of other programs (which usually
look in COMSPEC to find a shell fit for interactive use).
+=item PERL_ALLOW_NON_IFS_LSP (specific to the Win32 port)
+
+Set to 1 to allow the use of non-IFS compatible LSP's.
+Perl normally searches for an IFS-compatible LSP because this is required
+for its emulation of Windows sockets as real filehandles. However, this may
+cause problems if you have a firewall such as McAfee Guardian which requires
+all applications to use its LSP which is not IFS-compatible, because clearly
+Perl will normally avoid using such an LSP.
+Setting this environment variable to 1 means that Perl will simply use the
+first suitable LSP enumerated in the catalog, which keeps McAfee Guardian
+happy (and in that particular case Perl still works too because McAfee
+Guardian's LSP actually plays some other games which allow applications
+requiring IFS compatibility to work).
+
=item PERL_DEBUG_MSTATS
Relevant only if perl is compiled with the malloc included with the perl
this controls the behavior of global destruction of objects and other
references. See L<perlhack/PERL_DESTRUCT_LEVEL> for more information.
+=item PERL_DL_NONLAZY
+
+Set to one to have perl resolve B<all> undefined symbols when it loads
+a dynamic library. The default behaviour is to resolve symbols when
+they are used. Setting this variable is useful during testing of
+extensions as it ensures that you get an error on misspelled function
+names even if the test suite doesn't call it.
+
=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.
+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.
+
+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
+behaviour is B<not> to randomise unless the PERL_HASH_SEED is set.
+
+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<Please note that the hash seed is sensitive information>. Hashes are
+randomized to protect against local and remote attacks against Perl
+code. By manually setting a seed this protection may be partially or
+completely lost.
+
+See L<perlsec/"Algorithmic Complexity Attacks"> and
+L</PERL_HASH_SEED_DEBUG> for more information.
+
+=item PERL_HASH_SEED_DEBUG
+
+(Since Perl 5.8.1.) Set to one to display (to STDERR) the value of
+the hash seed at the beginning of execution. This, combined with
+L</PERL_HASH_SEED> is intended to aid in debugging nondeterministic
+behavior caused by hash randomization.
+
+B<Note that the hash seed is sensitive information>: by knowing it one
+can craft a denial-of-service attack against Perl code, even remotely,
+see L<perlsec/"Algorithmic Complexity Attacks"> for more information.
+B<Do not disclose the hash seed> to people who don't need to know it.
+See also hash_seed() of L<Hash::Util>.
+
=item PERL_ROOT (specific to the VMS port)
A translation concealed rooted logical name that contains perl and the
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 signals are used.
+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 C<delete $ENV{PERL_UNICODE}>).
-See the description of the C<-C> switch for more information.
+"disable Unicode", though (or alternatively unset PERL_UNICODE in
+your shell before starting Perl). See the description of the C<-C>
+switch for more information.
=item SYS$LOGIN (specific to the VMS port)
https://perl5.git.perl.org / perl5.git / blobdiff