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Meaning of $? (dollar question mark) in shell scripts
...when you hit enter, a fork + exec + wait happens like above, and bash then sets $? to the exit status of the forked process.
Note: for built-in commands like echo, a process need not be spawned, and Bash just sets $? to 0 to simulate an external process.
Standards and documentation
POSIX 7 2.5.2 "Sp...
PHP & mySQL: Year 2038 Bug: What is it? How to solve it?
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# update all rows by populating your new DATETIME field
UPDATE `myTable` SET `myTimestamp` = FROM_UNIXTIME(temp_myTimestamp);
# remove the temporary column
ALTER TABLE `myTable` DROP `temp_myTimestamp`
Resources
Year 2038 Problem (Wikipedia)
The Internet Will End in 30 Years
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Creating a simple XML file using python
...the standard library since 2.5)
LXML (Based on libxml2. Offers a rich superset of the ElementTree API as well XPath, CSS Selectors, and more)
Here's an example of how to generate your example document using the in-stdlib cElementTree:
import xml.etree.cElementTree as ET
root = ET.Element("root")...
Batch file. Delete all files and folders in a directory
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Use:
Create a batch file
Copy the below text into the batch file
set folder="C:\test"
cd /d %folder%
for /F "delims=" %%i in ('dir /b') do (rmdir "%%i" /s/q || del "%%i" /s/q)
It will delete all files and folders.
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Using the “start” command with parameters passed to the started program
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Instead of a batch file, you can create a shortcut on the desktop.
Set the target to:
"c:\program files\Microsoft Virtual PC\Virtual PC.exe" -pc "MY-PC" -launch
and you're all set. Since you're not starting up a command prompt to launch it, there will be no DOS Box.
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WAMP 403 Forbidden message on Windows 7
... Deny from all
Allow from 127.0.0.1
</Directory>
You can set them to allow connections from all IP addresses like follows :
AllowOverride All
Order allow,deny
Allow from all
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NSObject +load and +initialize - What do they do?
... for your class and once for each subclass. If you're doing something like setting up static variables, you'll want to guard against that: either with dispatch_once() or by testing self == [MyClass class].
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In git, is there a way to show untracked stashed files without applying the stash?
...cked), I added this alias to my config:
showstash = "!if test -z $1; then set -- 0; fi; git show --stat stash@{$1} && git show --stat stash@{$1}^3 2>/dev/null || echo No untracked files -"
It takes a single argument of which stash you want to view. Note it will still present it in two...
What are the mechanics of short string optimization in libc++?
... if accidentally mixed with a libc++ std::string compiled with a different setting of _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT will create run time errors.
I recommend this flag only be changed by a vendor of libc++.
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Plot two graphs in same plot in R
...ss to graphical object on every stage of plotting. Say, usual step-by-step setup can look like this:
g <- ggplot(df, aes(x))
g <- g + geom_line(aes(y=y1), colour="red")
g <- g + geom_line(aes(y=y2), colour="green")
g
g produces the plot, and you can see it at every stage (well, after cre...