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What is the best way to ensure only one instance of a Bash script is running? [duplicate]
...e
### HEADER ###
LOCKFILE="/var/lock/`basename $0`"
LOCKFD=99
# PRIVATE
_lock() { flock -$1 $LOCKFD; }
_no_more_locking() { _lock u; _lock xn && rm -f $LOCKFILE; }
_prepare_locking() { eval "exec $LOCKFD>\"$LOCKFILE\""; trap _no_more_locking EXIT; }
# ON START
_prepare_l...
Get the first element of each tuple in a list in Python [duplicate]
...
Use a list comprehension:
res_list = [x[0] for x in rows]
Below is a demonstration:
>>> rows = [(1, 2), (3, 4), (5, 6)]
>>> [x[0] for x in rows]
[1, 3, 5]
>>>
Alternately, you could use unpacking instead of x[0]:
res_li...
How do I pass parameters into a PHP script through a webpage?
...cript over the web) is using the query string and access them through the $_GET superglobal:
Go to http://yourdomain.com/path/to/script.php?argument1=arg1&argument2=arg2
... and access:
<?php
$argument1 = $_GET['argument1'];
$argument2 = $_GET['argument2'];
?>
If you want the script t...
Python debugging tips [closed]
...
PDB
You can use the pdb module, insert pdb.set_trace() anywhere and it will function as a breakpoint.
>>> import pdb
>>> a="a string"
>>> pdb.set_trace()
--Return--
> <stdin>(1)<module>()->None
(Pdb) p a
'a string'
(Pdb)
To...
JavaScript function similar to Python range()
...to xrange in Python2:
function range(low, high) {
return {
__iterator__: function() {
return {
next: function() {
if (low > high)
throw StopIteration;
return low++;
}
...
C library function to perform sort
... changed as per most suggestions. I draw the line, @ChrisL, at needing size_t since my arrays never get that big :-) And, @AndreyT, clever though that hack is, I prefer my code to be readable :-)
– paxdiablo
Nov 24 '09 at 11:44
...
How can I open a link in a new window?
...
window.open('url', 'window name', 'window settings')
jQuery:
$('a#link_id').click(function(){
window.open('url', 'window name', 'window settings');
return false;
});
You could also set the target to _blank actually.
...
How to list all properties of a PowerShell object
When I look at the Win32_ComputerSystem class , it shows loads of properties like Status , PowerManagementCapabilities , etc. However, when in PowerShell I do the below I only get back a couple:
...
Checking for empty queryset in Django
...is the code I refer to is only an example that it contains a line if not my_objects: to demonstrate that this is how they do it in the docs. All else is utterly irrelevant so I do not get your point. They could as well make a thousand queries and it would still be totally irrelevant as this is not t...
wkhtmltopdf: cannot connect to X server
...ble, so no need to make the wrapper script.
– jeffery_the_wind
Mar 13 '12 at 13:43
it worked for me.. in some situatio...