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Bash script to receive and repass quoted parameters
...# $4= "ddd ddd"
"$*" - quoted-dollar-star smashes the args into a single string (~1% of the time you actually want this behavior, eg in a conditional: if [[ -z "$*" ]]; then ...):
./quoted-dollar-star.sh aaa '' "'cc cc'" '"ddd ddd"'
# $1= aaa 'cc cc' "ddd ddd"
# $2=
...
Return 0 if field is null in MySQL
...) returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.
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How does IPython's magic %paste work?
...est_mode which allows you to copy paste example and test snippets from doc strings. This is also useful to execute interactive python session output that you could find in documentation and online forums, without having to first strip out the prompt strings.
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bash assign default value
...riable without needing to reassign
# colons suppress attempting to run the string
unset EGGS
: ${EGGS=spam}
echo 1 $EGGS # 1 spam
unset EGGS
: ${EGGS:=spam}
echo 2 $EGGS # 2 spam
EGGS=
: ${EGGS=spam}
echo 3 $EGGS # 3 (set, but blank -> leaves alone)
EGGS=
: ${EGGS:=spam}
echo ...
How to force 'cp' to overwrite directory instead of creating another one inside?
...
Be extra careful using this, as it will remove all files from bar, even hidden ones.
– Elia Grady
Jul 13 '17 at 8:20
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How to install the Raspberry Pi cross compiler on my Linux host machine?
...ow you should be able to compile your cmake programs simply by adding this extra flag: -D CMAKE_TOOLCHAIN_FILE=$HOME/raspberrypi/pi.cmake.
Using a cmake hello world example:
git clone https://github.com/jameskbride/cmake-hello-world.git
cd cmake-hello-world
mkdir build
cd build
cmake -D CMAKE_TO...
What is JavaScript garbage collection?
...called a "scavenger". A scavenger
may refer to a number, an object, a
string, whatever. We maintain a list
of scavengers -- variables are moved
on to the scav list when they come
into scope and off the scav list when
they go out of scope.
Every now and then the garbage
collector ru...
How to use OpenSSL to encrypt/decrypt files?
...bove!
-K key
The actual key to use: this must be represented as a string
comprised only of hex digits. If only the key is specified, the
IV must additionally be specified using the -iv option. When
both a key and a password are specified, the key given with the
-K option wi...
When is each sorting algorithm used? [closed]
...rantee no bad data gives you O(N^2), you should avoid it.
Merge-sort uses extra memory, but is particularly suitable for external sorting (i.e. huge files that don't fit into memory).
Heap-sort can sort in-place and doesn't have the worst case quadratic behavior, but on average is slower than quic...
What is the difference between .*? and .* regular expressions?
I'm trying to split up a string into two parts using regex. The string is formatted as follows:
3 Answers
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