SPUG: RE: One-liners on Windows via command.com
John W. Krahn
krahnj at telus.net
Wed Mar 23 21:52:38 PST 2005
Aaron W. West wrote:
> Don't forget percent signs!
>
> perldoc perlwin32 seems not to mention it:
>
> In CMD.EXE or COMMAND.COM, percent signs in pairs are interpolated, when
> determined to be a valid *and existing* variable name.
>
> It seems the solution is a backslash before the percent sign.
>
> It also appears that in a perl command line \cm means control-M (CR), and
> \cj means control-J (LF). I don't know where this is documented.
perldoc perlop
The following escape sequences are available in constructs that
interpolate and in transliterations.
\t tab (HT, TAB)
\n newline (NL)
\r return (CR)
\f form feed (FF)
\b backspace (BS)
\a alarm (bell) (BEL)
\e escape (ESC)
\033 octal char (ESC)
\x1b hex char (ESC)
\x{263a} wide hex char (SMILEY)
\c[ control char (ESC)
---------->^^
\N{name} named Unicode character
NOTE: Unlike C and other languages, Perl has no \v escape sequence for
the vertical tab (VT - ASCII 11).
The following escape sequences are available in constructs that
interpolate but not in transliterations.
\l lowercase next char
\u uppercase next char
\L lowercase till \E
\U uppercase till \E
\E end case modification
\Q quote non-word characters till \E
If "use locale" is in effect, the case map used by "\l", "\L", "\u" and
"\U" is taken from the current locale. See perllocale. If Unicode
(for example, "\N{}" or wide hex characters of 0x100 or beyond) is
being used, the case map used by "\l", "\L", "\u" and "\U" is as
defined by Unicode. For documentation of "\N{name}", see charnames.
All systems use the virtual "\n" to represent a line terminator, called
a "newline". There is no such thing as an unvarying, physical newline
character. It is only an illusion that the operating system, device
drivers, C libraries, and Perl all conspire to preserve. Not all
systems read "\r" as ASCII CR and "\n" as ASCII LF. For example, on a
Mac, these are reversed, and on systems without line terminator,
printing "\n" may emit no actual data. In general, use "\n" when you
mean a "newline" for your system, but use the literal ASCII when you
need an exact character. For example, most networking protocols expect
and prefer a CR+LF ("\015\012" or "\cM\cJ") for line terminators, and
-------------------------->^^^^^^^^^^^^^^^^^^^^^^
although they often accept just "\012", they seldom tolerate just
"\015". If you get in the habit of using "\n" for networking, you may
be burned some day.
John
--
use Perl;
program
fulfillment
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