Introduction

The following guide will go over the shell coding standard for the FreeNAS project.

In General

Style must be consistent with the surrounding code, in particular if it's contributed via a third party. This requirement has been established to be consistent with style(9)'s requirements in FreeBSD -- despite the fact that style(9) applies solely to C code.

Variable Declarations

• Variable names should be complete and descript. The reader should be able to discern what the intent of the variable is from the name.
• If your variable is multiword, it must be quoted in order to avoid word splitting in /bin/sh under FreeBSD.

Whitespace

• Use 72 columns as a soft limit and 79 columns as a hard limit.
• Use hard-tabs, instead of 4-space indentation. This is done to conform to the FreeBSD project shell coding style.

set -e and set -u

Using set -e and set -u will help the developer find potential bugs in his/her code related to bad exit codes and unset variables. If set -e is used in tandem with set -u, sh will stop whenever a variable is unset.

Conditionals and Loops

Conditionals should be composed in this format:

if :
then
    # This will always be executed
fi

while :
do
    # Do something here
    :
done

for :
do
    # Do something here
    :
done

Command substitution

• The $() format of command substitution is the preferred method.

Functions

Functions should be composed in this format:

name()
{
    # Function body
    :
}

Local variables

If the scope of a variable (even a loop variable) is local to the function, one should always be declared local.

Readonly variables

Constants in scripts should be sprinkled with readonly attributes to

1. Become self-documenting.
2. Make set -e more meaningful as set -e with readonly variables will cause a script to error out.

Miscellaneous Items

cat <<EOF >a-file
this is a multiline
message
EOF