sh Getting started with sh
Remarks
sh is not a single shell. Rather, it is a specification with the POSIX operating system standard for how a shell should work. A script that targets this specification can be executed by any POSIX-compliant shell, such as
bashkshashand its derivatives, such asdashzsh
In a POSIX-compliant operating system, the path /bin/sh refers to a POSIX-compliant shell. This is usually a shell that has features not found in the POSIX standard, but when run as sh, will restrict itself to the POSIX-compliant subset of its features.
References
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.
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!'
