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
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LEARN ABOUT PHP
get_magic_quotes_gpc
GET_MAGIC_QUOTES_GPC(3) 1 GET_MAGIC_QUOTES_GPC(3)get_magic_quotes_gpc - Gets the current configuration setting of magic_quotes_gpcSYNOPSIS
bool get_magic_quotes_gpc (void )
DESCRIPTION
Returns the current configuration setting of magic_quotes_gpc
Keep in mind that attempting to set magic_quotes_gpc at runtime will not work.
For more information about magic_quotes, see this security section.
RETURN VALUES
Returns 0 if magic_quotes_gpc is off, 1 otherwise. Or always returns FALSE as of PHP 5.4.0.
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.4.0 | |
| | |
| | Always returns FALSE because the magic quotes |
| | feature was removed from PHP. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
get_magic_quotes_gpc(3) example
<?php
// If magic quotes are enabled
echo $_POST['lastname']; // O'reilly
echo addslashes($_POST['lastname']); // O\'reilly
// Usage across all PHP versions
if (get_magic_quotes_gpc()) {
$lastname = stripslashes($_POST['lastname']);
}
else {
$lastname = $_POST['lastname'];
}
// If using MySQL
$lastname = mysql_real_escape_string($lastname);
echo $lastname; // O'reilly
$sql = "INSERT INTO lastnames (lastname) VALUES ('$lastname')";
?>
NOTES
Note
If the directive magic_quotes_sybase is ON it will completely override magic_quotes_gpc. So even when get_magic_quotes_gpc(3)
returns TRUE neither double quotes, backslashes or NUL's will be escaped. Only single quotes will be escaped. In this case they'll
look like: ''
SEE ALSO addslashes(3), stripslashes(3), get_magic_quotes_runtime(3), ini_get(3).
PHP Documentation Group GET_MAGIC_QUOTES_GPC(3)