In the [`InetAddressCacheUtilForOld`](../library/src/main/java/com/alibaba/dcm/internal/InetAddressCacheUtilForOld.java) class, the read and write to the DNS Cache also consistently adds a synchronized block with `addressCache` field as the lock to ensure thread safety.

Close

MD013 - Line length

Tags: line_length

Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)

This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.

This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.

You also have the option to exclude this rule for code blocks and tables. To do this, set the code_blocks and/or tables parameters to false.

Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.

<a href="https://github.com/alibaba/java-dns-cache-manipulator/releases/download/v1.8.3/dcm-1.8.3.tar.gz"><img src="https://img.shields.io/github/downloads/alibaba/java-dns-cache-manipulator/v1.8.3/dcm-1.8.3.tar.gz.svg?logoColor=white&logo=DocuSign" alt="GitHub release download - dcm.tar.gz)"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

<a href="https://github.com/alibaba/java-dns-cache-manipulator/releases/download/v1.8.3/dcm-1.8.3.tar.gz"><img src="https://img.shields.io/github/downloads/alibaba/java-dns-cache-manipulator/v1.8.3/dcm-1.8.3.tar.gz.svg?logoColor=white&logo=DocuSign" alt="GitHub release download - dcm.tar.gz)"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

cd ..

Close

Use a ( subshell ) to avoid having to cd back.

Problematic code:

for dir in */
do
  cd "$dir"
  convert index.png index.jpg
  cd ..
done

Correct code:

for dir in */
do
  (
  cd "$dir" || exit
  convert index.png index.jpg
  )
done

or

for dir in */
do
  cd "$dir" || exit
  convert index.png index.jpg
  cd ..
done

Rationale:

When doing cd dir; somestuff; cd .., cd dir can fail when permissions are lacking, if the dir was deleted, or if dir is actually a file.

In this case, somestuff will run in the wrong directory and cd .. will take you to an even more wrong directory. In a loop, this will likely cause the next cd to fail as well, propagating this error and running these commands far away from the intended directories.

Check cds exit status and/or use subshells to limit the effects of cd.

Exceptions

If you set variables you can't use a subshell. In that case, you should definitely check the exit status of cd, which will also silence this suggestion.

Notice

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

readonly BASE="$(cd $(dirname "$0")/..; pwd)"

Close

Quote this to prevent word splitting

Problematic code:

ls -l $(getfilename)

Correct code:

# getfilename outputs 1 file
ls -l "$(getfilename)"

# getfilename outputs multiple files, linefeed separated
getfilename | while IFS='' read -r line
do
  ls -l "$line"
done

Rationale:

When command expansions are unquoted, word splitting and globbing will occur. This often manifests itself by breaking when filenames contain spaces.

Trying to fix it by adding quotes or escapes to the data will not work. Instead, quote the command substitution itself.

If the command substitution outputs multiple pieces of data, use a loop instead.

Exceptions

In rare cases you actually want word splitting, such as in

gcc $(pkg-config --libs openssl) client.c

This is because pkg-config outputs -lssl -lcrypto, which you want to break up by spaces into -lssl and -lcrypto. An alternative is to put the variables to an array and expand it:

args=( $(pkg-config --libs openssl) )
gcc "${args[@]}" client.c

The power of using an array becomes evident when you want to combine, for example, the command result with user-provided arguments:

compile () {
    args=( $(pkg-config --libs openssl) "${@}" )
    gcc "${args[@]}" client.c
}
compile -DDEBUG
+ gcc -lssl -lcrypto -DDEBUG client.c

Notice

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

     export JAVA_HOME=`/usr/libexec/java_home`

Close

Declare and assign separately to avoid masking return values.

Problematic code:

export foo="$(mycmd)"

Correct code:

foo=$(mycmd)
export foo

Rationale:

In the original code, the return value of mycmd is ignored, and export will instead always return true. This may prevent conditionals, set -e and traps from working correctly.

When first marked for export and assigned separately, the return value of the assignment will be that of mycmd. This avoids the problem.

Exceptions:

If you intend to ignore the return value of an assignment, you can either ignore this warning or use

foo=$(mycmd) || true
export foo

Shellcheck does not warn about export foo=bar because bar is a literal and not a command substitution with an independent return value. It also does not warn about local -r foo=$(cmd), where declaration and assignment must be in the same command.

Notice

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

    JAVA_HOME="`(cd "$JAVA_HOME"; pwd)`"

Close

Use cd ... || exit in case cd fails.

Problematic code:

cd generated_files
rm -r *.c

func(){
  cd foo
  do_something
}

Correct code:

cd generated_files || exit
rm -r *.c

# For functions, you may want to use return:
func(){
  cd foo || return
  do_something
}

Rationale:

cd can fail for a variety of reasons: misspelled paths, missing directories, missing permissions, broken symlinks and more.

If/when it does, the script will keep going and do all its operations in the wrong directory. This can be messy, especially if the operations involve creating or deleting a lot of files.

To avoid this, make sure you handle the cases when cd fails. Ways to do this include

• cd foo || exit as suggested to just abort immediately
• if cd foo; then echo "Ok"; else echo "Fail"; fi for custom handling
• <(cd foo && cmd) as an alternative to <(cd foo || exit; cmd) in <(..), $(..) or ( )

Exceptions:

ShellCheck does not give this warning when cd is on the left of a || or &&, or the condition of a if, while or until loop. Having a set -e command anywhere in the script will disable this message, even though it won't necessarily prevent the issue.

If you are accounting for cd failures in a way shellcheck doesn't realize, you can disable this message with a [[directive]].

Notice

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

- 对于已经完成解析保存了`IP`的逻辑，设置`JVM DNS`缓存，不会生效！可以重新创建 连接或`Client`解决。  

Close

MD032 - Lists should be surrounded by blank lines

Tags: bullet, ul, ol, blank_lines

Aliases: blanks-around-lists

This rule is triggered when lists (of any kind) are either not preceded or not followed by a blank line:

Some text
* Some
* List

1. Some
2. List
Some text

To fix this, ensure that all lists have a blank line both before and after (except where the block is at the beginning or end of the document):

Some text

* Some
* List

1. Some
2. List

Some text

Rationale: Aside from aesthetic reasons, some parsers, including kramdown, will not parse lists that don't have blank lines before and after them.

Note: List items without hanging indents are a violation of this rule; list items with hanging indents are okay:

* This is
not okay

* This is
  okay

<a href="https://codeclimate.com/github/alibaba/java-dns-cache-manipulator"><img src="https://img.shields.io/codeclimate/maintainability/alibaba/java-dns-cache-manipulator?logo=code-climate" alt="Maintainability"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

<a href="https://search.maven.org/artifact/com.alibaba/dns-cache-manipulator"><img src="https://img.shields.io/maven-central/v/com.alibaba/dns-cache-manipulator?color=2d545e&logo=apache-maven&logoColor=white" alt="Maven Central"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

<a href="https://github.com/alibaba/java-dns-cache-manipulator/fork"><img src="https://img.shields.io/github/forks/alibaba/java-dns-cache-manipulator?style=flat" alt="GitHub Forks"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

<a href="https://github.com/alibaba/java-dns-cache-manipulator/network/dependents"><img src="https://badgen.net/github/dependents-repo/alibaba/java-dns-cache-manipulator?label=user%20repos" alt="user repos"></a>

Close

MD013 - Line length

Tags: line_length

Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)

This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.

This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.

You also have the option to exclude this rule for code blocks and tables. To do this, set the code_blocks and/or tables parameters to false.

Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.

<a href="https://codeclimate.com/github/alibaba/java-dns-cache-manipulator"><img src="https://img.shields.io/codeclimate/maintainability/alibaba/java-dns-cache-manipulator?logo=code-climate" alt="Maintainability"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

<a href="https://github.com/alibaba/java-dns-cache-manipulator/graphs/contributors"><img src="https://img.shields.io/github/contributors/alibaba/java-dns-cache-manipulator" alt="GitHub Contributors"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

<a href="https://github.com/alibaba/java-dns-cache-manipulator"><img src="https://img.shields.io/github/repo-size/alibaba/java-dns-cache-manipulator" alt="GitHub repo size"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

  local wdir=$(pwd)

Close

Declare and assign separately to avoid masking return values.

Problematic code:

export foo="$(mycmd)"

Correct code:

foo=$(mycmd)
export foo

Rationale:

In the original code, the return value of mycmd is ignored, and export will instead always return true. This may prevent conditionals, set -e and traps from working correctly.

When first marked for export and assigned separately, the return value of the assignment will be that of mycmd. This avoids the problem.

Exceptions:

If you intend to ignore the return value of an assignment, you can either ignore this warning or use

foo=$(mycmd) || true
export foo

Shellcheck does not warn about export foo=bar because bar is a literal and not a command substitution with an independent return value. It also does not warn about local -r foo=$(cmd), where declaration and assignment must be in the same command.

Notice

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

- [java InetAddress 的dns cache问题](http://www.blogjava.net/jjwwhmm/archive/2008/07/09/213685.html)，

Close

MD032 - Lists should be surrounded by blank lines

Tags: bullet, ul, ol, blank_lines

Aliases: blanks-around-lists

This rule is triggered when lists (of any kind) are either not preceded or not followed by a blank line:

Some text
* Some
* List

1. Some
2. List
Some text

To fix this, ensure that all lists have a blank line both before and after (except where the block is at the beginning or end of the document):

Some text

* Some
* List

1. Some
2. List

Some text

Rationale: Aside from aesthetic reasons, some parsers, including kramdown, will not parse lists that don't have blank lines before and after them.

Note: List items without hanging indents are a violation of this rule; list items with hanging indents are okay:

* This is
not okay

* This is
  okay

- [Domain Name System - wikipedia](http://en.wikipedia.org/wiki/Domain_Name_System)

Close

MD032 - Lists should be surrounded by blank lines

Tags: bullet, ul, ol, blank_lines

Aliases: blanks-around-lists

This rule is triggered when lists (of any kind) are either not preceded or not followed by a blank line:

Some text
* Some
* List

1. Some
2. List
Some text

To fix this, ensure that all lists have a blank line both before and after (except where the block is at the beginning or end of the document):

Some text

* Some
* List

1. Some
2. List

Some text

Rationale: Aside from aesthetic reasons, some parsers, including kramdown, will not parse lists that don't have blank lines before and after them.

Note: List items without hanging indents are a violation of this rule; list items with hanging indents are okay:

* This is
not okay

* This is
  okay

<a href="https://github.com/alibaba/java-dns-cache-manipulator/stargazers"><img src="https://img.shields.io/github/stars/alibaba/java-dns-cache-manipulator?style=flat" alt="GitHub Stars"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.

<a href="https://gitpod.io/#https://github.com/alibaba/java-dns-cache-manipulator"><img src="https://img.shields.io/badge/Gitpod-ready to code-339933?label=gitpod&logo=gitpod&logoColor=white" alt="gitpod: Ready to Code"></a>

Close

MD033 - Inline HTML

Tags: html

Aliases: no-inline-html

This rule is triggered whenever raw HTML is used in a markdown document:

Inline HTML header

To fix this, use 'pure' markdown instead of including raw HTML:

# Markdown header

Rationale: Raw HTML is allowed in markdown, but this rule is included for those who want their documents to only include "pure" markdown, or for those who are rendering markdown documents in something other than HTML.