Term::ANSIColor
Term::ANSIColor(3) Perl Programmers Reference Guide Term::ANSIColor(3)
NAME
Term::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::ANSIColor qw(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 SYNOP-
SIS).
color() takes any number of strings as arguments and considers them to
be space-separated lists of attributes. It then forms and returns the
escape sequence to set those attributes. 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, underscore, 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 back-
ground color.
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 typing changed to weird col-
ors.
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. Alternately, 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 arguments as text
to colorize.
Normally, colored() just puts attribute codes at the beginning 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 con-
fused 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, CON-
CEALED, 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::ANSI-
Color::AUTORESET to a true value. Then, the display mode will auto-
matically be reset if there is no comma after the constant. In other
words, with that variable set:
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 constants inter-
face 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 subroutines 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 col-
ored().
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:
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() contains 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 functions 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 original 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 variable 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 con-
stants 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 (generally 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 peripher-
als.
Note that not all displays are ISO 6429-compliant, or even
X3.64-compliant (or are even attempting to be so). This 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 Win-
dows NT or Windows 2000. They may just be ignored, or they may dis-
play as an ESC character followed by some apparent garbage.
Jean Delvare provided the following table of different common 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 implementation
under Cygwin on Windows NT, and Mac Terminal is the Terminal applica-
tion in Mac OS X. Where the entry is other than yes or no, that emu-
lator displays the given attribute as something else instead. Note
that on an aixterm, 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 (strikethrough) 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 over-
lining. As none of these attributes are widely supported or useful,
they also aren’t currently supported 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/stan-
dards/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 available for free, there seems little rea-
son to obtain the ISO 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 combined 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@stan-
ford.edu> and Zenin. This program is free software; you may redis-
tribute it and/or modify it under the same terms as Perl itself.
perl v5.8.8 2001-09-21 Term::ANSIColor(3)
