How does one output bold text in Bash?

Question

The most compatible way of doing this is using tput to discover the right sequences to send to the terminal:

bold=$(tput bold)
normal=$(tput sgr0)

then you can use the variables $bold and $normal to format things:

echo "this is ${bold}bold${normal} but this isn't"

gives

this is bold but this isn't

In order to apply a style on your string, you can use a command like:

echo -e '\033[1mYOUR_STRING\033[0m'

Explanation:

• echo -e - The -e option means that escaped (backslashed) strings will be interpreted
• \033 - escaped sequence represents beginning/ending of the style
• lowercase m - indicates the end of the sequence
• 1 - Bold attribute (see below for more)
• [0m - resets all attributes, colors, formatting, etc.

The possible integers are:

• 0 - Normal Style
• 1 - Bold
• 2 - Dim
• 3 - Italic
• 4 - Underlined
• 5 - Blinking
• 7 - Reverse
• 8 - Invisible

I assume bash is running on a vt100-compatible terminal in which the user did not explicitly turn off the support for formatting.

First, turn on support for special characters in echo, using -e option. Later, use ansi escape sequence ESC[1m, like:

echo -e "\033[1mSome Text"

More on ansi escape sequences for example here: ascii-table.com/ansi-escape-sequences-vt-100.php

In theory like so:

# BOLD
$ echo -e "\033[1mThis is a BOLD line\033[0m"
This is a BOLD line

# Using tput
tput bold 
echo "This" #BOLD
tput sgr0 #Reset text attributes to normal without clear.
echo "This" #NORMAL

# UNDERLINE
$ echo -e "\033[4mThis is a underlined line.\033[0m"
This is a underlined line. 

But in practice it may be interpreted as "high intensity" color instead.

(source: http://unstableme.blogspot.com/2008/01/ansi-escape-sequences-for-writing-text.html)