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How to output only captured groups with sed?
...as well as specifying what you do want.
string='This is a sample 123 text and some 987 numbers'
echo "$string" | sed -rn 's/[^[:digit:]]*([[:digit:]]+)[^[:digit:]]+([[:digit:]]+)[^[:digit:]]*/\1 \2/p'
This says:
don't default to printing each line (-n)
exclude zero or more non-digits
include on...
How to use shared memory with Linux in C
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There are two approaches: shmget and mmap. I'll talk about mmap, since it's more modern and flexible, but you can take a look at man shmget (or this tutorial) if you'd rather use the old-style tools.
The mmap() function can be used to allocate memory buffer...
Print commit message of a given commit in git
I need a plumbing command to print the commit message of one given commit - nothing more, nothing less.
6 Answers
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Hidden features of Python [closed]
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In case you're thinking it's doing 1 < x, which comes out as True, and then comparing True < 10, which is also True, then no, that's really not what happens (see the last example.) It's really translating into 1 < x and x < 10, and x < 10 and 10 < x * 10 and x*10 < 100, but...
Error java.lang.OutOfMemoryError: GC overhead limit exceeded
...n excessive amount of time (by default 98% of all CPU time of the process) and recovers very little memory in each run (by default 2% of the heap).
This effectively means that your program stops doing any progress and is busy running only the garbage collection at all time.
To prevent your applica...
Can I use a binary literal in C or C++?
... 2 formatting with STL streams (since setbase will only honour bases 8, 10 and 16), but you can use either a std::string version of itoa, or (the more concise, yet marginally less efficient) std::bitset.
#include <boost/utility/binary.hpp>
#include <stdio.h>
#include <stdlib.h>
#i...
Progress indicator during pandas operations
I regularly perform pandas operations on data frames in excess of 15 million or so rows and I'd love to have access to a progress indicator for particular operations.
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Why is “while ( !feof (file) )” always wrong?
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I'd like to provide an abstract, high-level perspective.
Concurrency and simultaneity
I/O operations interact with the environment. The environment is not part of your program, and not under your control. The environment truly exists "concurrently" with your program. As with all things concurr...
'echo' without newline in a shell script
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There are multiple versions of the echo command, with different behaviors. Apparently the shell used for your script uses a version that doesn't recognize -n.
The printf command has much more consistent behavior. echo is fine for simple things like echo hello, but I s...
Merge 2 arrays of objects
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This is so far the simplest use and works just fine. Thanks for sharing it.
– Leo Caseiro
Jun 22 '16 at 7:51
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