This will give you the array var. You can access the values in var via
$(...) means run the command between the braces and give me the result.
var=( $(...) ) means run the command between the braces and save the result in an array called var. So should be able to capture the output from any command this way.
For an explanation of [[ -s ... ]] see
[[ ... ]] && ... || ...
is a short form of if ... then ... else.
If you have other questions you should open a new post a give an exact description of your problem and your goal.
Hi all,
My boss wants me to find out how often e-m users are accessing their account:confused:. The mail server keeps log of all logins. I want to use grep the 'usernames', but it should come out the moment it first encounters the username in the log. Can I do that? I want to avoid 10+ greps... (2 Replies)
I have seen this used several times but not really sure of what it actually does. I am confused with the second grep as the argument to the first.
some commands | grep -v grep | some other commands
Can anyone provide an explanation?
Thanks, (5 Replies)
Never mind, I did more research, and now am using grep -v './temp/', dumping it into a new text file, then using mv -f to make that the original file. Thanks for reading!
---------------
Hi folks, I haven't done any scripting in years, and now I have a problem. Our backup tapes are filling... (0 Replies)
Hello. I'm a complete newbie to C programming. I have a C program that wasn't written by me where I need to write some wrappers around it to automate and make it easier for a client to use. The problem is that the program accepts standard input to control the program... I'm hoping to find a simple... (6 Replies)
How come grep testfile1 won't find anything in testfile1 (even though the characters sd are there in great quantity), but grep '' testfile1 will find plenty?
Do the single quotes prevent the shell from interpreting the testfile1 is interpreted as: grep *test whether or not characters sd exist*... (5 Replies)
This should be so easy...
I want to find all the apps in /Applications that start with the lower case i (e.g. iTunes.app, iSync.app, iCal.app) They should all have the .app extension. I've tried:
ls /Applications |grep -o i*.app
ls /Applications/i*.app
Anyhow, I just want to see what apps... (2 Replies)
I'm trying to write a simple script to identify every user who tried to “sudo” on the system. I have the first portion down to grep the log file
grep “sudo” /var/log/secure.
What I want to do is have the script identify the person just one time not every instance the user tried... (4 Replies)
I hope someone can help me.
I have a folder e.g. /opt/application
Under that are many sub folders e.g.
Folder1
Folder2
Folder3
Folder4
Folder5
Folder6
etc
In some of these fodlers (not all of them) is a file called errors.log
I need to run a grep that will start at... (3 Replies)
Cheers!
In /etc/syslog.conf, if an error type is not specified, is it logged anywhere (most preferable is it logged to /var/log/messages) or not?
To be more precise I am interested in error and critical level messages. At default these errors are not specified in syslog.conf, and I need to... (6 Replies)
Discussion started by: dr1zzt3r
6 Replies
LEARN ABOUT PHP
empty
EMPTY(3) 1 EMPTY(3)empty - Determine whether a variable is emptySYNOPSIS
bool empty (mixed $var)
DESCRIPTION
Determine whether a variable is considered to be empty. A variable is considered empty if it does not exist or if its value equals FALSE.
empty(3) does not generate a warning if the variable does not exist.
PARAMETERS
o $var
- Variable to be checked
Note
Prior to PHP 5.5, empty(3) only supports variables; anything else will result in a parse error. In other words, the follow-
ing will not work: empty(trim($name)). Instead, use trim($name) == false.
No warning is generated if the variable does not exist. That means empty(3) is essentially the concise equivalent to !isset($var)
|| $var == false.
RETURN VALUES
Returns FALSE if $var exists and has a non-empty, non-zero value. Otherwise returns TRUE.
The following things are considered to be empty:
o "" (an empty string)
o 0 (0 as an integer)
o 0.0 (0 as a float)
o "0" (0 as a string)
o NULL
o FALSE
o array() (an empty array)
o $var; (a variable declared, but without a value)
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.5.0 | |
| | |
| | empty(3) now supports expressions, rather than |
| | only variables. |
| | |
| 5.4.0 | |
| | |
| | Checking non-numeric offsets of strings returns |
| | TRUE. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
A simple empty(3) / isset(3) comparison.
<?php
$var = 0;
// Evaluates to true because $var is empty
if (empty($var)) {
echo '$var is either 0, empty, or not set at all';
}
// Evaluates as true because $var is set
if (isset($var)) {
echo '$var is set even though it is empty';
}
?>
Example #2
empty(3) on String Offsets
PHP 5.4 changes how empty(3) behaves when passed string offsets.
<?php
$expected_array_got_string = 'somestring';
var_dump(empty($expected_array_got_string['some_key']));
var_dump(empty($expected_array_got_string[0]));
var_dump(empty($expected_array_got_string['0']));
var_dump(empty($expected_array_got_string[0.5]));
var_dump(empty($expected_array_got_string['0.5']));
var_dump(empty($expected_array_got_string['0 Mostel']));
?>
Output of the above example in PHP 5.3:
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
Output of the above example in PHP 5.4:
bool(true)
bool(false)
bool(false)
bool(false)
bool(true)
bool(true)
NOTES
Note
Because this is a language construct and not a function, it cannot be called using variable functions.
Note
When using empty(3) on inaccessible object properties, the __isset() overloading method will be called, if declared.
SEE ALSO isset(3), __isset(), unset(3), array_key_exists(3), count(3), strlen(3), The type comparison tables.
PHP Documentation Group EMPTY(3)