Getting started with sh

Hello, world!

With echo:

$ echo Hello, world!
Hello, world!

With printf:

$ printf 'Hello, world!\n'
Hello, world!

As a file:

#!/bin/sh
printf '%s\n' 'Hello, world!'

Echo Portability

$ for shell in ash bash dash ksh ksh93 zsh; do
>     $shell -c "echo '\\\\'$shell'\\\\'"
> done
\\ash\\
\\bash\\
\dash\
\pdksh\
\\ksh93\\
\zsh\

’echo’ can only be used consistently, across implementations, if its arguments do not contain any backslashes (reverse-solidi), and if the first argument does not start with a dash (hyphen-minus). Many implementations allow additional options, such as -e, even though the only option allowed is -n (see below).

From POSIX:

If the first operand is -n, or if any of the operands contain a character, the results are implementation-defined.