How to use echo command in Linux? (Detailed explanation of usage)

The echo command is one of the most basic and commonly used commands in Linux. It outputs the string passed as argument to standard output. The following article will introduce you to the usage of the echo command. I hope it will be helpful to you. [Recommended related video tutorials: Linux tutorial]

##Linux echo command## The #echo command is a shell built into Bash and is often used in shell scripts to display messages or output the results of other commands.

The syntax of the echo command is as follows:

echo [-neE] [ARGUMENTS]

The parameters of the echo command:

-n

: When the -n option is specified, subsequent line breaks are suppressed; that is, there will be no automatic line break at the end.

-e

: When the -e option is specified, the following backslash escape characters will be interpreted: ●　

\\

- Inserts a backslash (\) character. ●

\a

- Alert (BEL)●

\b

- Displays backspace characters. ●

\c

- Suppresses any further output●

\e

- Displays escape characters. ●

\f

- Display form feed character. ●　

\n

- Display a new line. ●　

\r

- Display carriage return. ●　

\t

- Display horizontal tabs. ●　

\v

- Displays vertical tabs.

-E

: Disables interpretation of escape characters when the -E option is specified, which is the default.

There are several points to consider when using the echo command:

● Before passing arguments to the echo command, the shell will replace all variables, wildcard matches, and special character.

●Although not necessary, it is a good programming practice to enclose arguments passed to the echo command in double or single quotes.

●When using single quotes (

''

), the literal value of each character contained in the quotes will be retained. Variables and commands will not be expanded.

Usage examples of Linux echo command
Let’s take a look at how to use the echo command through the following examples:

Example 1: Display a line of text on standard output.

echo Hello, World!

Output:

Hello, World!

Example 2: Display text lines containing double quotes

To output double quotes, you need to surround them Within single quotes, or escape it using the backslash character.

echo 'Hello "Linuxize"'

or

echo "Hello \"Linuxize\""

Output:

Hello "Linuxize"

Example 3: Display text lines containing single quotes

To print single quotes , need to be enclosed in double quotes, or use ANSI-C quotes.

echo "I'm a Linux user."

or

echo $'I\'m a Linux user.'

Output:

I'm a Linux user.

Example 4: Display messages containing special characters

Use the -e option to Enables parsing of escape characters.

echo -e "You know nothing, Jon Snow.\n\t- Ygritte"

Output:

You know nothing, Jon Snow.
    - Ygritte

Example 5: Return the names of all .php files in the current directory

Description: The echo command can match pattern characters used together, such as wildcards.

echo The PHP files are: *.php

Output:

The PHP files are: index.php contact.php functions.php

Example 6: Redirect to file

We can use, The >> operator redirects output to a file instead of displaying it on the screen. <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'>echo -e &amp;#39;The only true wisdom is in knowing you know nothing.\nSocrates&amp;#39; &gt;&gt; /tmp/file.txt</pre><div class="contentsignin">Copy after login</div></div> Description: If file.txt does not exist, it will be created. When using , the file will be overwritten; when using , the output will be appended to the file. Use the cat command to view the contents of the file:

cat /tmp/file.txt

Output:

The only true wisdom is in knowing you know nothing.
Socrates

Example 7: Display variables

echo also Variables can be displayed. For example, we want to display the name of the currently logged in user

echo $USER

Output:

linuxuser

Description:

$USER

is a shell variable.

Example 8: Display command output

Use the

$ (command

) expression to pass the command output as a parameter to echo. The following command will display the current date: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'>echo &quot;The date is: $(date +%D)&quot;</pre><div class="contentsignin">Copy after login</div></div> Output:

The date is: 04/18/19

The above is the entire content of this article, I hope it will be helpful to everyone's study. For more exciting content, you can pay attention to the relevant tutorial columns of the PHP Chinese website! ! !

The above is the detailed content of How to use echo command in Linux? (Detailed explanation of usage). For more information, please follow other related articles on the PHP Chinese website!