How to print a warning sign (triangle with exclamation point)?

Question

I am interested in including a triangle with an exclamation point (unicode #9888: ⚠) in a tex document. I've looked in the usual places (detexify, etc.) and not found this symbol. The document should be compilable with pdflatex and the source should have ASCII encoding. I already have a tikz version that I like reasonably well, given by

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric}
\newcommand{\warningsign}{\tikz[baseline=-.75ex] \node[shape=regular polygon, regular polygon sides=3, inner sep=0pt, draw, thick] {\textbf{!}};}
\begin{document}
\warningsign Warning
\end{document}

so I am also requiring that the answer be an actual character, or at least not done using graphics.

Answer 1

The fourier package provides \warning:

\documentclass{article}
\usepackage{fourier}
\begin{document}
\warning
\end{document}

I sometimes find that some of the fourier commands conflict with other packages I use, so if I only want this symbol I do:

\documentclass{article}
\begin{document}
{\fontencoding{U}\fontfamily{futs}\selectfont\char 49\relax}
\end{document}

which is essentially what \warning does. This requires the futs font family which is provided with the fourier package, so the package must still be installed even though it's not actually being loaded.

If the futs font isn't available, the transcript will show the message:

LaTeX Font Warning: Font shape `U/futs/m/n' undefined
(Font)              using `U/cmr/m/n' instead on input line 5.

This means that the cmr font is being used instead, which has something else in the \char 49 slot.

Answer 2

A \warning symbol (previously \danger) is provided by the fourier package (see The Comprehensive LATEX Symbol List, table 475, page 177).

If you don't have the need for the complete fourier package, but you want to use that symbol, you can extract it and use in your document:

\newcommand*{\TakeFourierOrnament}[1]{{%
\fontencoding{U}\fontfamily{futs}\selectfont\char#1}}
\newcommand*{\danger}{\TakeFourierOrnament{66}}

MWE

\documentclass{article}
\newcommand{\TakeFourierOrnament}[1]{{%
\fontencoding{U}\fontfamily{futs}\selectfont\char#1}}
\newcommand{\danger}{\TakeFourierOrnament{66}}
\begin{document}
\danger
\end{document}

Output

Answer 3

A simple build assigned to the unicode symbol, so you can use ⚠ or \Warning:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{xcolor}
\usepackage{newunicodechar}

\newcommand\Warning{%
 \makebox[1.4em][c]{%
 \makebox[0pt][c]{\raisebox{.1em}{\small!}}%
 \makebox[0pt][c]{\color{red}\Large$\bigtriangleup$}}}%

\newunicodechar{⚠}{\Warning}

\begin{document}

    Do⚠not⚠put your finger

    on the power plug.

\end{document}

Answer 4

Here, I choose to build my own by overlaying a black, tiny ! atop a red $\triangle$, and then scaling the result to a desired [optional] size

\documentclass{article}
\usepackage{stackengine}
\usepackage{scalerel}
\usepackage{xcolor}
\newcommand\dangersign[1][2ex]{%
  \renewcommand\stacktype{L}%
  \scaleto{\stackon[1.3pt]{\color{red}$\triangle$}{\tiny !}}{#1}%
}
\begin{document}
This is a danger sign 5ex tall: \dangersign[5ex]\par
Here is the default (2ex) size: \dangersign
\end{document}

Zoom of result, to clarify my response to Charles' comment.

If one prefers a bolder !, just make it \bfseries:

\documentclass{article}
\usepackage{stackengine}
\usepackage{scalerel}
\usepackage{xcolor}
\newcommand\dangersign[1][2ex]{%
  \renewcommand\stacktype{L}%
  \scaleto{\stackon[1.3pt]{\color{red}$\triangle$}{\tiny\bfseries !}}{#1}%
}
\begin{document}
This is a danger sign 5ex tall: \dangersign[5ex]\par
Here is the default (2ex) size: \dangersign
\end{document}

Answer 5

When you use XeLaTeX or LuaLaTeX you can simply use the character as is:

\documentclass{article}
\usepackage{fontspec}
\setmainfont[Ligatures=TeX]{STIXGeneral}
\newcommand\warningsign{⚠}
\begin{document}
    \warningsign Warning
\end{document}

Of course the font must contain it. (STIX does.)

It looks like this:

Notice that it is more common to give unicode code points in hexadecimal, here U+26A0.

If you don’t want to have unusual characters in your source code, you can specify the warning sign by its code point:

\newcommand\warningsign{\symbol{"26A0}}

(Found at “How do I enter an arbitrary Unicode code point into my document?”)

Answer 6

The package fontawesome provides the commands \faWarning (equiv., \faExclamationTriangle for the warning icon, which looks like this:

A minimal example would be:

\documentclass{article}
\usepackage{fontawesome}

\begin{document}

\faWarning\, Warning: This product contains peanuts, %
which might not be very suitable for certain individuals.

\end{document}

The fontawesome package might be new, but it provides a wide range of high-quality web icons, and that makes it pretty relevant tool in terms of modern typesetting and design.

Answer 7

\documentclass{article}
\usepackage{tikz}
\begin{document}
\newcommand\danger[1][]{%
\begin{tikzpicture}[baseline=-0.5ex, inner xsep=0pt,#1]
\node[]{$\triangle$};
\node[yshift=0.125ex, scale=0.45]{!};
\end{tikzpicture}\space}
A danger-sing \danger is shown here.
\huge A danger-sing \danger[red] is shown here.
\end{document}