Term::ANSIColor(3Perl Programmers Reference GuTerm::ANSIColor(3p)NAMETerm::ANSIColor - Color screen output using ANSI escape
sequences
SYNOPSIS
use Term::ANSIColor;
print color 'bold blue';
print "This text is bold blue.\n";
print color 'reset';
print "This text is normal.\n";
print colored ("Yellow on magenta.\n", 'yellow on_magenta');
print "This text is normal.\n";
print colored ['yellow on_magenta'], "Yellow on magenta.\n";
use Term::ANSIColorqw(uncolor);
print uncolor '01;31', "\n";
use Term::ANSIColor qw(:constants);
print BOLD, BLUE, "This text is in bold blue.\n", RESET;
use Term::ANSIColor qw(:constants);
$Term::ANSIColor::AUTORESET = 1;
print BOLD BLUE "This text is in bold blue.\n";
print "This text is normal.\n";
DESCRIPTION
This module has two interfaces, one through color() and
colored() and the other through constants. It also offers
the utility function uncolor(), which has to be explicitly
imported to be used (see SYNOPSIS).
color() takes any number of strings as arguments and consid-
ers them to be space-separated lists of attributes. It then
forms and returns the escape sequence to set those attri-
butes. It doesn't print it out, just returns it, so you'll
have to print it yourself if you want to (this is so that
you can save it as a string, pass it to something else, send
it to a file handle, or do anything else with it that you
might care to).
uncolor() performs the opposite translation, turning escape
sequences into a list of strings.
The recognized attributes (all of which should be fairly
intuitive) are clear, reset, dark, bold, underline, under-
score, blink, reverse, concealed, black, red, green, yellow,
blue, magenta, on_black, on_red, on_green, on_yellow,
on_blue, on_magenta, on_cyan, and on_white. Case is not
significant. Underline and underscore are equivalent, as
are clear and reset, so use whichever is the most intuitive
to you. The color alone sets the foreground color, and
on_color sets the background color.
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Note that not all attributes are supported by all terminal
types, and some terminals may not support any of these
sequences. Dark, blink, and concealed in particular are
frequently not implemented.
Attributes, once set, last until they are unset (by sending
the attribute "reset"). Be careful to do this, or otherwise
your attribute will last after your script is done running,
and people get very annoyed at having their prompt and typ-
ing changed to weird colors.
As an aid to help with this, colored() takes a scalar as the
first argument and any number of attribute strings as the
second argument and returns the scalar wrapped in escape
codes so that the attributes will be set as requested before
the string and reset to normal after the string. Alter-
nately, you can pass a reference to an array as the first
argument, and then the contents of that array will be taken
as attributes and color codes and the remainder of the argu-
ments as text to colorize.
Normally, colored() just puts attribute codes at the begin-
ning and end of the string, but if you set
$Term::ANSIColor::EACHLINE to some string, that string will
be considered the line delimiter and the attribute will be
set at the beginning of each line of the passed string and
reset at the end of each line. This is often desirable if
the output is being sent to a program like a pager that can
be confused by attributes that span lines. Normally you'll
want to set $Term::ANSIColor::EACHLINE to "\n" to use this
feature.
Alternately, if you import ":constants", you can use the
constants CLEAR, RESET, BOLD, DARK, UNDERLINE, UNDERSCORE,
BLINK, REVERSE, CONCEALED, BLACK, RED, GREEN, YELLOW, BLUE,
MAGENTA, CYAN, WHITE, ON_BLACK, ON_RED, ON_GREEN, ON_YELLOW,
ON_BLUE, ON_MAGENTA, ON_CYAN, and ON_WHITE directly. These
are the same as color('attribute') and can be used if you
prefer typing:
print BOLD BLUE ON_WHITE "Text\n", RESET;
to
print colored ("Text\n", 'bold blue on_white');
When using the constants, if you don't want to have to
remember to add the ", RESET" at the end of each print line,
you can set $Term::ANSIColor::AUTORESET to a true value.
Then, the display mode will automatically be reset if there
is no comma after the constant. In other words, with that
variable set:
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print BOLD BLUE "Text\n";
will reset the display mode afterwards, whereas:
print BOLD, BLUE, "Text\n";
will not.
The subroutine interface has the advantage over the con-
stants interface in that only two subroutines are exported
into your namespace, versus twenty-two in the constants
interface. On the flip side, the constants interface has
the advantage of better compile time error checking, since
misspelled names of colors or attributes in calls to color()
and colored() won't be caught until runtime whereas
misspelled names of constants will be caught at compile
time. So, polute your namespace with almost two dozen sub-
routines that you may not even use that often, or risk a
silly bug by mistyping an attribute. Your choice, TMTOWTDI
after all.
DIAGNOSTICS
Bad escape sequence %s
(F) You passed an invalid ANSI escape sequence to
uncolor().
Bareword "%s" not allowed while "strict subs" in use
(F) You probably mistyped a constant color name such as:
$Foobar = FOOBAR . "This line should be blue\n";
or:
@Foobar = FOOBAR, "This line should be blue\n";
This will only show up under use strict (another good
reason to run under use strict).
Invalid attribute name %s
(F) You passed an invalid attribute name to either
color() or colored().
Name "%s" used only once: possible typo
(W) You probably mistyped a constant color name such as:
print FOOBAR "This text is color FOOBAR\n";
It's probably better to always use commas after constant
names in order to force the next error.
No comma allowed after filehandle
(F) You probably mistyped a constant color name such as:
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print FOOBAR, "This text is color FOOBAR\n";
Generating this fatal compile error is one of the main
advantages of using the constants interface, since
you'll immediately know if you mistype a color name.
No name for escape sequence %s
(F) The ANSI escape sequence passed to uncolor() con-
tains escapes which aren't recognized and can't be
translated to names.
ENVIRONMENT
ANSI_COLORS_DISABLED
If this environment variable is set, all of the func-
tions defined by this module (color(), colored(), and
all of the constants not previously used in the program)
will not output any escape sequences and instead will
just return the empty string or pass through the origi-
nal text as appropriate. This is intended to support
easy use of scripts using this module on platforms that
don't support ANSI escape sequences.
For it to have its proper effect, this environment vari-
able must be set before any color constants are used in
the program.
RESTRICTIONS
It would be nice if one could leave off the commas around
the constants entirely and just say:
print BOLD BLUE ON_WHITE "Text\n" RESET;
but the syntax of Perl doesn't allow this. You need a comma
after the string. (Of course, you may consider it a bug
that commas between all the constants aren't required, in
which case you may feel free to insert commas unless you're
using $Term::ANSIColor::AUTORESET.)
For easier debuging, you may prefer to always use the commas
when not setting $Term::ANSIColor::AUTORESET so that you'll
get a fatal compile error rather than a warning.
NOTES
The codes generated by this module are standard terminal
control codes, complying with ECMA-48 and ISO 6429 (gen-
erally referred to as "ANSI color" for the color codes).
The non-color control codes (bold, dark, italic, underline,
and reverse) are part of the earlier ANSI X3.64 standard for
control sequences for video terminals and peripherals.
Note that not all displays are ISO 6429-compliant, or even
X3.64-compliant (or are even attempting to be so). This
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module will not work as expected on displays that do not
honor these escape sequences, such as cmd.exe, 4nt.exe, and
command.com under either Windows NT or Windows 2000. They
may just be ignored, or they may display as an ESC character
followed by some apparent garbage.
Jean Delvare provided the following table of different com-
mon terminal emulators and their support for the various
attributes and others have helped me flesh it out:
clear bold dark under blink reverse conceal
------------------------------------------------------------------------
xterm yes yes no yes bold yes yes
linux yes yes yes bold yes yes no
rxvt yes yes no yes bold/black yes no
dtterm yes yes yes yes reverse yes yes
teraterm yes reverse no yes rev/red yes no
aixterm kinda normal no yes no yes yes
PuTTY yes color no yes no yes no
Windows yes no no no no yes no
Cygwin SSH yes yes no color color color yes
Mac Terminal yes yes no yes yes yes yes
Windows is Windows telnet, Cygwin SSH is the OpenSSH imple-
mentation under Cygwin on Windows NT, and Mac Terminal is
the Terminal application in Mac OS X. Where the entry is
other than yes or no, that emulator displays the given
attribute as something else instead. Note that on an aix-
term, clear doesn't reset colors; you have to explicitly set
the colors back to what you want. More entries in this
table are welcome.
Note that codes 3 (italic), 6 (rapid blink), and 9 (strik-
ethrough) are specified in ANSI X3.64 and ECMA-048 but are
not commonly supported by most displays and emulators and
therefore aren't supported by this module at the present
time. ECMA-048 also specifies a large number of other
attributes, including a sequence of attributes for font
changes, Fraktur characters, double-underlining, framing,
circling, and overlining. As none of these attributes are
widely supported or useful, they also aren't currently sup-
ported by this module.
SEE ALSO
ECMA-048 is available on-line (at least at the time of this
writing) at
<http://www.ecma-international.org/publications/standards/ECMA-048.HTM>.
ISO 6429 is available from ISO for a charge; the author of
this module does not own a copy of it. Since the source
material for ISO 6429 was ECMA-048 and the latter is avail-
able for free, there seems little reason to obtain the ISO
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standard.
The current version of this module is always available from
its web site at
<http://www.eyrie.org/~eagle/software/ansicolor/>. It is
also part of the Perl core distribution as of 5.6.0.
AUTHORS
Original idea (using constants) by Zenin, reimplemented
using subs by Russ Allbery <rra@stanford.edu>, and then com-
bined with the original idea by Russ with input from Zenin.
Russ Allbery now maintains this module.
COPYRIGHT AND LICENSE
Copyright 1996, 1997, 1998, 2000, 2001, 2002 Russ Allbery
<rra@stanford.edu> and Zenin. This program is free
software; you may redistribute it and/or modify it under the
same terms as Perl itself.
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