Difference between echo `ls -l` and echo "`ls -l`" ?
Hi guys,
Been messing around with shell programming for a couple of days and I found something that was pretty odd in the behavior of the echo command. Below is an example-:
When I type the following in my /home directory from my lxterminal in Debian-:
echo "`ls -l`"
I get the following output-:
Now this is what I expected. I know whatever is put in ` ` is suppose to interpreted as a command in the BASH echo. So, therefore this is the expected output of ls -l on my /home directory.
But it gets weird when I remove the " " (double quotes) from the echo statement.
When I run the following-:
echo `ls -l`
I get as output the following-:
If you look closely you will see that it is exactly identical to the output that is given above except for the fact that it contains no line breaks. My question is why ?
Why are the line-breaks removed when I remove the double quotes from echo ? Whatever is there in ` `(tild signs) is supposed to be interpreted as a command right ?
If removal of double quotes " " means that there is a change in the meaning of the echo, then please tell me what is the special meaning that double quotes has in echo ?
Is there any difference between echo "$SHELL" and echo $SHELL ? I know the output is same but since one has double quotes and one doesn't is there any difference in the way that BASH treats them internally ?
I am using Debian Wheezy LXDE with Bash 4.2.
Thanks.
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Discussion started by: marcink
2 Replies
LEARN ABOUT PHP
round
ROUND(3) 1 ROUND(3)round - Rounds a floatSYNOPSIS
float round (float $val, [int $precision], [int $mode = PHP_ROUND_HALF_UP])
DESCRIPTION
Returns the rounded value of $val to specified $precision (number of digits after the decimal point). $precision can also be negative or
zero (default).
Note
PHP doesn't handle strings like "12,300.2" correctly by default. See converting from strings.
PARAMETERS
o $val
- The value to round
o $precision
- The optional number of decimal digits to round to.
o $mode
- Use one of the following constants to specify the mode in which rounding occurs.
+--------------------+---------------------------------------------------+
| Constant | |
| | |
| | Description |
| | |
+--------------------+---------------------------------------------------+
| | |
| PHP_ROUND_HALF_UP | |
| | |
| | Round $val up to $precision decimal places away |
| | from zero, when it is half way there. Making 1.5 |
| | into 2 and -1.5 into -2. |
| | |
| | |
|PHP_ROUND_HALF_DOWN | |
| | |
| | Round $val down to $precision decimal places |
| | towards zero, when it is half way there. Making |
| | 1.5 into 1 and -1.5 into -1. |
| | |
| | |
|PHP_ROUND_HALF_EVEN | |
| | |
| | Round $val to $precision decimal places towards |
| | the next even value. |
| | |
| | |
|PHP_ROUND_HALF_ODD | |
| | |
| | Round $val to $precision decimal places towards |
| | the next odd value. |
| | |
+--------------------+---------------------------------------------------+
RETURN VALUES
The rounded value
EXAMPLES
Example #1
round(3) examples
<?php
echo round(3.4); // 3
echo round(3.5); // 4
echo round(3.6); // 4
echo round(3.6, 0); // 4
echo round(1.95583, 2); // 1.96
echo round(1241757, -3); // 1242000
echo round(5.045, 2); // 5.05
echo round(5.055, 2); // 5.06
?>
Example #2
$mode examples
<?php
echo round(9.5, 0, PHP_ROUND_HALF_UP); // 10
echo round(9.5, 0, PHP_ROUND_HALF_DOWN); // 9
echo round(9.5, 0, PHP_ROUND_HALF_EVEN); // 10
echo round(9.5, 0, PHP_ROUND_HALF_ODD); // 9
echo round(8.5, 0, PHP_ROUND_HALF_UP); // 9
echo round(8.5, 0, PHP_ROUND_HALF_DOWN); // 8
echo round(8.5, 0, PHP_ROUND_HALF_EVEN); // 8
echo round(8.5, 0, PHP_ROUND_HALF_ODD); // 9
?>
Example #3
$mode with precision examples
<?php
/* Using PHP_ROUND_HALF_UP with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_UP); // 1.6
echo round( 1.54, 1, PHP_ROUND_HALF_UP); // 1.5
echo round(-1.55, 1, PHP_ROUND_HALF_UP); // -1.6
echo round(-1.54, 1, PHP_ROUND_HALF_UP); // -1.5
/* Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_DOWN); // 1.5
echo round( 1.54, 1, PHP_ROUND_HALF_DOWN); // 1.5
echo round(-1.55, 1, PHP_ROUND_HALF_DOWN); // -1.5
echo round(-1.54, 1, PHP_ROUND_HALF_DOWN); // -1.5
/* Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_EVEN); // 1.6
echo round( 1.54, 1, PHP_ROUND_HALF_EVEN); // 1.5
echo round(-1.55, 1, PHP_ROUND_HALF_EVEN); // -1.6
echo round(-1.54, 1, PHP_ROUND_HALF_EVEN); // -1.5
/* Using PHP_ROUND_HALF_ODD with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_ODD); // 1.5
echo round( 1.54, 1, PHP_ROUND_HALF_ODD); // 1.5
echo round(-1.55, 1, PHP_ROUND_HALF_ODD); // -1.5
echo round(-1.54, 1, PHP_ROUND_HALF_ODD); // -1.5
?>
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.3.0 | |
| | |
| | The $mode parameter was introduced. |
| | |
| 5.2.7 | |
| | |
| | The inner workings of round(3) was changed to |
| | conform to the C99 standard. |
| | |
+--------+---------------------------------------------------+
SEE ALSO ceil(3), floor(3), number_format(3).
PHP Documentation Group ROUND(3)