This cop makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

This cop makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

This cop makes sure that all methods use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
def fooBar; end

# good
def foo_bar; end

Example: EnforcedStyle: camelCase

# bad
def foo_bar; end

# good
def fooBar; end

This cop checks for uses of class variables. Offenses are signaled only on assignment to class variables to reduce the number of offenses that would be reported.

This cop checks hash literal syntax.

It can enforce either the use of the class hash rocket syntax or the use of the newer Ruby 1.9 syntax (when applicable).

A separate offense is registered for each problematic pair.

The supported styles are:

• ruby19 - forces use of the 1.9 syntax (e.g. {a: 1}) when hashes have all symbols for keys
• hash_rockets - forces use of hash rockets for all hashes
• nomixedkeys - simply checks for hashes with mixed syntaxes
• ruby19nomixed_keys - forces use of ruby 1.9 syntax and forbids mixed syntax hashes

Example: EnforcedStyle: ruby19 (default)

# bad
{:a => 2}
{b: 1, :c => 2}

# good
{a: 2, b: 1}
{:c => 2, 'd' => 2} # acceptable since 'd' isn't a symbol
{d: 1, 'e' => 2} # technically not forbidden

Example: EnforcedStyle: hash_rockets

# bad
{a: 1, b: 2}
{c: 1, 'd' => 5}

# good
{:a => 1, :b => 2}

Example: EnforcedStyle: nomixedkeys

# bad
{:a => 1, b: 2}
{c: 1, 'd' => 2}

# good
{:a => 1, :b => 2}
{c: 1, d: 2}

Example: EnforcedStyle: ruby19nomixed_keys

# bad
{:a => 1, :b => 2}
{c: 2, 'd' => 3} # should just use hash rockets

# good
{a: 1, b: 2}
{:c => 3, 'd' => 4}

This cop makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

$/${} is unnecessary on arithmetic variables.

Problematic code:

echo $(($n+1))

Correct code:

echo $((n+1))

Rationale:

The $ on regular variables in arithmetic contexts is unnecessary, and can even lead to subtle bugs. This is because the contents of $((..)) is first expanded into a string, and then evaluated as an expression:

$ a='1+1'
$ echo $(($a * 5))    # becomes 1+1*5
6
$ echo $((a * 5))     # evaluates as (1+1)*5
10

The $ is unavoidable for special variables like $1 vs 1, $# vs #. It's also required when adding modifiers to parameters expansions, like ${#var} or ${var%-}. ShellCheck does not warn about these cases.

Notice

Original content from the ShellCheck https://github.com/koalaman/shellcheck/wiki.

This cop makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

This cop checks for missing top-level documentation of classes and modules. Classes with no body are exempt from the check and so are namespace modules - modules that have nothing in their bodies except classes, other modules, or constant definitions.

The documentation requirement is annulled if the class or module has a "#:nodoc:" comment next to it. Likewise, "#:nodoc: all" does the same for all its children.

Example:

# bad
class Person
  # ...
end

# good
# Description/Explanation of Person class
class Person
  # ...
end

This cop checks for uses of class variables. Offenses are signaled only on assignment to class variables to reduce the number of offenses that would be reported.

To read lines rather than words, pipe/redirect to a 'while read' loop.

Problematic code:

for line in $(cat file | grep -v '^ *#')
do
  echo "Line: $line"
done

Correct code:

grep -v '^ *#' < file | while IFS= read -r line
do
  echo "Line: $line"
done

or without a subshell (bash, zsh, ksh):

while IFS= read -r line
do
  echo "Line: $line"
done < <(grep -v '^ *#' < file)

or without a subshell, with a pipe (more portable, but write a file on the filesystem):

mkfifo mypipe
grep -v '^ *#' < file > mypipe &
while IFS= read -r line
do
  echo "Line: $line"
done < mypipe
rm mypipe

Rationale:

For loops by default (subject to $IFS) read word by word. Additionally, glob expansion will occur.

Given this text file:

foo *
bar

The for loop will print:

Line: foo
Line: aardwark.jpg
Line: bullfrog.jpg
...

The while loop will print:

Line: foo *
Line: bar

Exceptions

If you want to read word by word, you should still use a while read loop (e.g. with read -a to read words into an array).

Rare reasons for ignoring this message is if you don't care because your file only contains numbers and you're not interested in good practices, or if you've set $IFS appropriately and also disabled globbing.

Notice

Original content from the ShellCheck https://github.com/koalaman/shellcheck/wiki.

This cop checks for uses of class variables. Offenses are signaled only on assignment to class variables to reduce the number of offenses that would be reported.

This cop checks for uses of class variables. Offenses are signaled only on assignment to class variables to reduce the number of offenses that would be reported.

This cop checks the indentation of the first line of the right-hand-side of a multi-line assignment.

Example:

# bad
value =
if foo
  'bar'
end

# good
value =
  if foo
    'bar'
  end

The indentation of the remaining lines can be corrected with other cops such as IndentationConsistency and EndAlignment.

This cop checks for rescuing StandardError. There are two supported styles implicit and explicit. This cop will not register an offense if any error other than StandardError is specified.

Example: EnforcedStyle: implicit

# `implicit` will enforce using `rescue` instead of
# `rescue StandardError`.

# bad
begin
  foo
rescue StandardError
  bar
end

# good
begin
  foo
rescue
  bar
end

# good
begin
  foo
rescue OtherError
  bar
end

# good
begin
  foo
rescue StandardError, SecurityError
  bar
end

Example: EnforcedStyle: explicit (default)

# `explicit` will enforce using `rescue StandardError`
# instead of `rescue`.

# bad
begin
  foo
rescue
  bar
end

# good
begin
  foo
rescue StandardError
  bar
end

# good
begin
  foo
rescue OtherError
  bar
end

# good
begin
  foo
rescue StandardError, SecurityError
  bar
end

Here we check if the parameters on a multi-line method call or definition are aligned.

Example: EnforcedStyle: withfirstparameter (default)

# good

foo :bar,
    :baz

# bad

foo :bar,
  :baz

Example: EnforcedStyle: withfixedindentation

# good

foo :bar,
  :baz

# bad

foo :bar,
    :baz

This cop makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

This cop checks for methods invoked via the :: operator instead of the . operator (like FileUtils::rmdir instead of FileUtils.rmdir).

Example:

# bad
Timeout::timeout(500) { do_something }
FileUtils::rmdir(dir)
Marshal::dump(obj)

# good
Timeout.timeout(500) { do_something }
FileUtils.rmdir(dir)
Marshal.dump(obj)

This cop checks for uses of class variables. Offenses are signaled only on assignment to class variables to reduce the number of offenses that would be reported.