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Full Discussion: Explaination on if true
Top Forums Shell Programming and Scripting Explaination on if true Post 302889793 by Don Cragun on Monday 24th of February 2014 01:23:57 AM
Old 02-24-2014
Quote:
Originally Posted by chandana hs
Hi Team,
I need to know why ppl use If true loop instead of just writing down the sequence of code lines.
1:
Code:
echo "Line1"
if true; then
echo "Line2"
fi
echo "Line3"

2:
Code:
echo "Line1"
echo "Line2"
echo "Line3"

Could you explain what does the if true loop make difference in 1st compare to 2nd code?

Regards,
Chandana
I'm not sure what you mean by "if true loop". There is no loop here.

The only time I have seen code like this is during development where true is a placeholder for code to be added later. (But that should never be done without including a comment describing what code needs to be added.)

I have, however, e seen true used as the condition in a while loop to create an obvious infinite loop or a loop where the termination condition occurs in the middle of the loop instead of at the start of the loop or the end of the loop as in:
Code:
echo line1
while true
do      echo line2
        other stuff
        if [ something_failed ]
        then    break
        fi
        more stuff
done
echo line3

This User Gave Thanks to Don Cragun For This Post:
 

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ECHO(3) 								 1								   ECHO(3)

echo - Output one or more strings

SYNOPSIS
void echo (string $arg1, [string $...]) DESCRIPTION
Outputs all parameters. echo is not actually a function (it is a language construct), so you are not required to use parentheses with it. echo (unlike some other language constructs) does not behave like a function, so it cannot always be used in the context of a function. Additionally, if you want to pass more than one parameter to echo, the parameters must not be enclosed within parentheses. echo also has a shortcut syntax, where you can immediately follow the opening tag with an equals sign. Prior to PHP 5.4.0, this short syn- tax only works with the short_open_tag configuration setting enabled. I have <?=$foo?> foo. PARAMETERS
o $arg1 - The parameter to output. o $... - RETURN VALUES
No value is returned. EXAMPLES
Example #1 echo examples <?php echo "Hello World"; echo "This spans multiple lines. The newlines will be output as well"; echo "This spans multiple lines. The newlines will be output as well."; echo "Escaping characters is done "Like this"."; // You can use variables inside of an echo statement $foo = "foobar"; $bar = "barbaz"; echo "foo is $foo"; // foo is foobar // You can also use arrays $baz = array("value" => "foo"); echo "this is {$baz['value']} !"; // this is foo ! // Using single quotes will print the variable name, not the value echo 'foo is $foo'; // foo is $foo // If you are not using any other characters, you can just echo variables echo $foo; // foobar echo $foo,$bar; // foobarbarbaz // Some people prefer passing multiple parameters to echo over concatenation. echo 'This ', 'string ', 'was ', 'made ', 'with multiple parameters.', chr(10); echo 'This ' . 'string ' . 'was ' . 'made ' . 'with concatenation.' . " "; echo <<<END This uses the "here document" syntax to output multiple lines with $variable interpolation. Note that the here document terminator must appear on a line with just a semicolon. no extra whitespace! END; // Because echo does not behave like a function, the following code is invalid. ($some_var) ? echo 'true' : echo 'false'; // However, the following examples will work: ($some_var) ? print 'true' : print 'false'; // print is also a construct, but // it behaves like a function, so // it may be used in this context. echo $some_var ? 'true': 'false'; // changing the statement around ?> NOTES
Note Because this is a language construct and not a function, it cannot be called using variable functions. SEE ALSO
print(3), printf(3), flush(3), Heredoc syntax. PHP Documentation Group ECHO(3)
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