scans for the first line starting with #! and containing the word
"perl", and starts there instead. This is useful for running a script
embedded in a larger message. (In this case you would indicate the end
-of the script using the __END__ token.)
+of the script using the C<__END__> token.)
The #! line is always examined for switches as the line is being
parsed. Thus, if you're on a machine that allows only one argument
After locating your script, Perl compiles the entire script to an
internal form. If there are any compilation errors, execution of the
script is not attempted. (This is unlike the typical shell script,
-which might run partway through before finding a syntax error.)
+which might run part-way through before finding a syntax error.)
If the script is syntactically correct, it is executed. If the script
runs off the end without hitting an exit() or die() operator, an implicit
as the first line in C<*.cmd> file (C<-S> due to a bug in cmd.exe's
`extproc' handling).
-=item DOS
+=item MS-DOS
Create a batch file to run your script, and codify it in
C<ALTERNATIVE_SHEBANG> (see the F<dosish.h> file in the source
The Win95/NT installation, when using the Activeware port of Perl,
will modify the Registry to associate the .pl extension with the perl
-interpreter. If you install another port, or (eventually) build your
-own Win95/NT Perl using WinGCC, then you'll have to modify the
-Registry yourself.
+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.
=item Macintosh
-Macintosh perl scripts will have the the appropriate Creator and
+Macintosh perl scripts will have the appropriate Creator and
Type, so that double-clicking them will invoke the perl application.
=back
# Unix
perl -e 'print "Hello world\n"'
- # DOS, etc.
+ # MS-DOS, etc.
perl -e "print \"Hello world\n\""
- # Mac
+ # Macintosh
print "Hello world\n"
(then Run "Myscript" or Shift-Command-R)
perl -e "print ""Hello world\n"""
The problem is that none of this is reliable: it depends on the command
-tirely possible neither works. If 4DOS was the command shell, I'd
-probably have better luck like this:
+and it is entirely possible neither works. If 4DOS was the command shell, this would
+probably work better:
- perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>""
+ perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>""
CMD.EXE in Windows NT slipped a lot of standard Unix functionality in
when nobody was looking, but just try to find documentation for its
quoting rules.
-Under the Mac, it depends which environment you are using. The MacPerl
+Under the Macintosh, it depends which environment you are using. The MacPerl
shell, or MPW, is much like Unix shells in its support for several
-quoting variants, except that it makes free use of the Mac's non-ASCII
+quoting variants, except that it makes free use of the Macintosh's non-ASCII
characters as control characters.
-I'm afraid that there is no general solution to all of this. It is a
-mess, pure and simple.
-
-[Some of this answer was contributed by Kenneth Albanowski.]
+There is no general solution to all of this. It's just a mess.
=head2 Switches
causes Perl to check the syntax of the script and then exit without
executing it. Actually, it I<will> execute C<BEGIN>, C<END>, and C<use> blocks,
-because these are considered as occurring outside the execution of
+because these are considered as occurring outside the execution of
your program.
=item B<-d>
=item B<-e> I<commandline>
-may be used to enter one line of script.
+may be used to enter one line of script.
If B<-e> is given, Perl
-will not look for a script filename in the argument list.
+will not look for a script filename in the argument list.
Multiple B<-e> commands may
-be given to build up a multi-line script.
+be given to build up a multi-line script.
Make sure to use semicolons where you would in a normal program.
=item B<-F>I<pattern>
the selected filehandle. Note that STDOUT is restored as the
default output filehandle after the loop.
-You can use C<eof> without parenthesis to locate the end of each input file,
-in case you want to append to each file, or reset line numbering (see
+You can use C<eof> without parenthesis to locate the end of each input file,
+in case you want to append to each file, or reset line numbering (see
example in L<perlfunc/eof>).
=item B<-I>I<directory>
If the first character after the C<-M> or C<-m> is a dash (C<->)
then the 'use' is replaced with 'no'.
-A little built-in syntactic sugar means you can also say
+A little builtin syntactic sugar means you can also say
C<-mmodule=foo,bar> or C<-Mmodule=foo,bar> as a shortcut for
C<-M'module qw(foo bar)'>. This avoids the need to use quotes when
importing symbols. The actual code generated by C<-Mmodule=foo,bar> is
}
Note that the lines are not printed by default. See B<-p> to have
-lines printed. Here is an efficient way to delete all files older than
-a week:
+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:
find . -mtime +7 -print | perl -nle 'unlink;'
while (<>) {
... # your script goes here
} continue {
- print;
+ print or die "-p destination: $!\n";
}
-Note that the lines are printed automatically. To suppress printing
-use the B<-n> switch. A B<-p> overrides a B<-n> switch.
+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. Note that the
+lines are printed automatically. An error occuring during printing is
+treated as fatal. To suppress printing use the B<-n> switch. A B<-p>
+overrides a B<-n> switch.
C<BEGIN> and C<END> blocks may be used to capture control before or after
the implicit loop, just as in awk.
=item B<-S>
makes Perl use the PATH environment variable to search for the
-script (unless the name of the script starts with a slash). Typically
-this is used to emulate #! startup on machines that don't support #!,
-in the following manner:
+script (unless the name of the script contains directory separators).
+On some platforms, this also makes Perl append suffixes to the
+filename while searching for it. For example, on Win32 platforms,
+the ".bat" and ".cmd" suffixes are appended if a lookup for the
+original name fails, and if the name does not already end in one
+of those suffixes. If your Perl was compiled with DEBUGGING turned
+on, using the -Dp switch to Perl shows how the search progresses.
+
+If the file supplied contains directory separators (i.e. it is an
+absolute or relative pathname), and if the file is not found,
+platforms that append file extensions will do so and try to look
+for the file with those extensions added, one by one.
+
+On DOS-like platforms, if the script does not contain directory
+separators, it will first be searched for in the current directory
+before being searched for on the PATH. On Unix platforms, the
+script will be searched for strictly on the PATH.
+
+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:
#!/usr/bin/perl
eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
use lib "/my/directory";
+=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]>
+switches are allowed. When running taint checks (because the script
+was running setuid or setgid, or the B<-T> switch was used), this
+variable is ignored.
+
=item PERLLIB
A colon-separated list of directories in which to look for Perl library
BEGIN { require 'perl5db.pl' }
+=item PERL5SHELL (specific to WIN32 port)
+
+May be set to an alternative shell that perl must use internally for
+executing "backtick" commands or system(). Perl doesn't use COMSPEC
+for this purpose because COMSPEC has a high degree of variability
+among users, leading to portability concerns. Besides, perl can use
+a shell that may not be 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).
+
=item PERL_DEBUG_MSTATS
Relevant only if your perl executable was built with B<-DDEBUGGING_MSTATS>,
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'};
+ $ENV{PATH} = '/bin:/usr/bin'; # or whatever you need
+ $ENV{SHELL} = '/bin/sh' if exists $ENV{SHELL};
+ delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};
projects / p5sagit/p5-mst-13.2.git / blobdiff