Linux: List All Environment Variables Command

How do I display all my environment variables using bash shell on RHEL / Debian / Ubuntu / CentOS / Fedora / Mint Linux operating systems?

You can use any one of the following command to display the environment variables and their values.

Tutorial details
Difficulty	Easy (rss)
Root privileges	No
Requirements	None
Estimated completion time	1m

a) printenv command - Print all or part of environment.

b) env command - Print all exported environment or run a program in a modified environment.

c) set command - Print the name and value of each shell variable.

Examples

I recommend that you use the printenv command:

printenv

OR

printenv | less

OR

printenv | more

Sample outputs:

Fig.01: Command to see a list of all currently defined environment variables in a Linux bash terminal

A list of the commonly used variables in Linux

System Variable	Meaning	To View Variable Value Type
BASH_VERSION	Holds the version of this instance of bash.	echo $BASH_VERSION
HOSTNAME	The name of the your computer.	echo $HOSTNAME
CDPATH	The search path for the cd command.	echo $CDPATH
HISTFILE	The name of the file in which command history is saved.	echo $HISTFILE
HISTFILESIZE	The maximum number of lines contained in the history file.	echo $HISTFILESIZE
HISTSIZE	The number of commands to remember in the command history. The default value is 500.	echo $HISTSIZE
HOME	The home directory of the current user.	echo $HOME
IFS	The Internal Field Separator that is used for word splitting after expansion and to split lines into words with the read builtin command. The default value is <space><tab><newline>.	echo $IFS
LANG	Used to determine the locale category for any category not specifically selected with a variable starting with LC_.	echo $LANG
PATH	The search path for commands. It is a colon-separated list of directories in which the shell looks for commands.	echo $PATH
PS1	Your prompt settings.	echo $PS1
TMOUT	The default timeout for the read builtin command. Also in an interactive shell, the value is interpreted as the number of seconds to wait for input after issuing the command. If not input provided it will logout user.	echo $TMOUT
TERM	Your login terminal type.	echo $TERM export TERM=vt100
SHELL	Set path to login shell.	echo $SHELL
DISPLAY	Set X display name	echo $DISPLAY export DISPLAY=:0.1
EDITOR	Set name of default text editor.	export EDITOR=/usr/bin/vim

set and env command

You can use the env / set command too:

 
env
env | more
set
set | more
 

Sample outputs:

HOME=/home/vivek
vivek@nas01:~$ env
TERM=xterm-256color
SHELL=/bin/bash
XDG_SESSION_COOKIE=9ee90112ba2cb349f07bfe2f00002e46-1381581541.324726-906214463
SSH_CLIENT=192.168.1.6 60190 22
SSH_TTY=/dev/pts/1
USER=vivek
MAIL=/var/mail/vivek
PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
PWD=/home/vivek
LANG=en_IN
SHLVL=1
HOME=/home/vivek
LANGUAGE=en_IN:en
LOGNAME=vivek
SSH_CONNECTION=192.168.1.6 60190 192.168.1.10 22
_=/usr/bin/env

A note about env/set command

The env will only display a list of environment variables that have been exported and it will not show all bash variables. The set command allows you to change the values of shell options and set the positional parameters, or to display the names and values of shell variables. If no options or arguments are supplied, set displays the names and values of all shell variables and functions, sorted according to the current locale, in a format that may be reused as input for setting or resetting the currently-set variables. Hence, I recommend that you use printenv command to dump the list of all shell variables on screen. To save the list of all shell environment variables to a file, enter:

 
printenv > env.txt
cat env.txt
 

Use the grep command to search for particular variable:

 
printenv | grep foo
printenv | grep HOME
 

RECOMMEND READINGS

• Bash shell variables from the Linux shell scripting wiki.
• Man pages: printenv(1), bash(1), env(1)

ref: http://www.cyberciti.biz/faq/linux-list-all-environment-variables-env-command/

replaceAll vào String object

// Replaces all instances of the given substring.
String.prototype.replaceAll = function(
strTarget, // The substring you want to replace
strSubString // The string you want to replace in.
){
var strText = this;
var intIndexOfMatch = strText.indexOf( strTarget );
 
// Keep looping while an instance of the target string
// still exists in the string.
while (intIndexOfMatch != -1){
// Relace out the current instance.
strText = strText.replace( strTarget, strSubString )
 
// Get the index of any next matching substring.
intIndexOfMatch = strText.indexOf( strTarget );
}
 
// Return the updated string with ALL the target strings
// replaced out with the new substring.
return( strText );
}

1

alert(myString.replaceAll('my', 'his')); //output : "his blog of his friend here".

how to get ServletContext from jsp

JSPs in Weblogic behaves differently from Tomcat with respect to getServletContext

ServletContext sc = getServletConfig().getServletContext();

javascript-error-uncaught-syntaxerror-unexpected-end-of-input

Add a second });.

When properly indented, your code reads

$(function() {
    $("#mewlyDiagnosed").hover(function() {
        $("#mewlyDiagnosed").animate({'height': '237px', 'top': "-75px"});
    }, function() {
        $("#mewlyDiagnosed").animate({'height': '162px', 'top': "0px"});
    });
MISSING!

You never closed the outer $(function() {.

Spring MVC ajax request with UTF 8 support

Recently for my Dropbox Writer project, I ran into a issue with transferring none English characters between server and client side. There are not a lot of solutions on the web and those solutions are very inconsistent.

Explain my situation

I created a Spring MVC project what can create text files in Dropbox. Dropbox uses UTF 8 for text encoding, thus it supports non English characters. My application uses ajax to drive rest service calls to transfer data between html based client side and spring mvc based server side. I’ve added CharacterEncodingFilter to the web.xml as following:

<filter> <filter-name>CharacterEncodingFilter</filter-name> <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> <init-param> <param-name>forceEncoding</param-name> <param-value>true</param-value> </init-param> </filter>

The problem

When I create a file with name contains Chinese characters, the returned file name is scrambled. The problem is my application uses @ResponseBody in my restful ajax calls to produce json data but those data is not returned in UTF 8 format.

I’ve spent sometime researching and testing a few solutions and I want to share those with you.

Solution 1

Don’t use @ResponseBody. Return void in the controller, and use HtppServletResponse to return string with valid formatting.

@RequestMapping(value = "/rest/create/document") public void create(Document document, HttpServletRespone respone) throws UnsupportedEncodingException {   Document newDocument = DocumentService.create(Document);   String json = jsonSerializer.serialize(newDocument);   OutputStream outputStream = respones.getOutputStream();   outputStream.write(json.getBytes("UTF-8"));   outputStream.close(); }

Advantage: This will always output text with correct text format, and it’s very simple to understand.

Disadvantage: Very cumbersome. You are going away from the Spring MVC model and writing directly to the HttpServlet model.

Solution 2

Return the an Response Entity object and set it’s content type.

@RequestMapping(value = "/rest/create/document") public ResponseEntity<String> create(Document document, HttpServletRespone respone)   HttpHeaders responseHeaders = new HttpHeaders();   responseHeaders.add("Content-Type", "text/html; charset=utf-8");   Document newDocument = DocumentService.create(Document);   String json = jsonSerializer.serialize(newDocument);   return new ResponseEntity<String>(json, responseHeaders, HttpStatus.OK); }

Better then the last solution, but you still feel there is a lot of plumbing involved.

Solution 3

This is it; this is the most elegant solution and it took me a while to figure out.

@RequestMapping(value = "/rest/create/document", produces = "text/plain;charset=UTF-8") @ResponseBody public String create(Document document, HttpServletRespone respone) throws UnsupportedEncodingException {   Document newDocument = DocumentService.create(Document);   return jsonSerializer.serialize(newDocument); }

When I saw this solution, it blown my mind. Yes this is really that simple. There is no plumbing, you tell spring mvc directly how to return formatted text. The downside is you will always need to return UTF 8 text.

json spring mvc java

@RequestMapping(value = "/rest/create/document", produces = "text/plain;charset=UTF-8")
@ResponseBody
public String create(Document document, HttpServletRespone respone) throws UnsupportedEncodingException {

    Document newDocument = DocumentService.create(Document);

    return jsonSerializer.serialize(newDocument);
}

<mvc:annotation-driven>
  <mvc:message-converters register-defaults="true">
    <bean class="org.springframework.http.converter.StringHttpMessageConverter">
      <property name="supportedMediaTypes" value = "text/plain;charset=UTF-8" />
    </bean>
  </mvc:message-converters>
</mvc:annotation-driven>

Or code-based configuration:
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {

  private static final Charset UTF8 = Charset.forName("UTF-8");

  @Override
  public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    StringHttpMessageConverter stringConverter = new StringHttpMessageConverter();
    stringConverter.setSupportedMediaTypes(Arrays.asList(new MediaType("text", "plain", UTF8)));
    converters.add(stringConverter);

    // Add other converters ...
  }
}