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How can I select random files from a directory in bash?
I have a directory with about 2000 files. How can I select a random sample of N files through using either a bash script or a list of piped commands?
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Extracting the last n characters from a string in R
...se R, but it's straight-forward to make a function to do this using substr and nchar:
x <- "some text in a string"
substrRight <- function(x, n){
substr(x, nchar(x)-n+1, nchar(x))
}
substrRight(x, 6)
[1] "string"
substrRight(x, 8)
[1] "a string"
This is vectorised, as @mdsumner point...
Regex exactly n OR m times
...ou are doing it is fine.
An alternative is:
X{m}(X{k})?
where m < n and k is the value of n-m.
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Replace multiple characters in a C# string
...\n]{2}/\n/g
s/ at the beginning means a search
The characters between [ and ] are the characters to search for (in any order)
The second / delimits the search-for text and the replace text
In English, this reads:
"Search for ; or , or \t or \r or (space) or exactly two sequential \n and repla...
Regular expression matching a multiline block of text
...e.MULTILINE)
I think your biggest problem is that you're expecting the ^ and $ anchors to match linefeeds, but they don't. In multiline mode, ^ matches the position immediately following a newline and $ matches the position immediately preceding a newline.
Be aware, too, that a newline can consi...
Applicatives compose, monads don't
What does the above statement mean? And when is one preferable to other?
5 Answers
5
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What is the exact meaning of IFS=$'\n'?
...ot exactly so -- \n is just an (escaped) letter n. You are right that '\n' and "\n" are backlash followed by n.
– Roman Cheplyaka
Nov 8 '10 at 23:08
15
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Renaming files in a folder to sequential numbers
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Try to use a loop, let, and printf for the padding:
a=1
for i in *.jpg; do
new=$(printf "%04d.jpg" "$a") #04 pad to length of 4
mv -i -- "$i" "$new"
let a=a+1
done
using the -i flag prevents automatically overwriting existing files.
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Repeat String - Javascript
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Note to new readers: This answer is old and and not terribly practical - it's just "clever" because it uses Array stuff to get
String things done. When I wrote "less process" I definitely meant
"less code" because, as others have noted in subsequent answers, it...
Limit a stream by a predicate
...tream.iterator(), wrap the Iterator to have a "take-while" implementation, and then go back to a Spliterator and then a Stream. Or -- maybe -- wrap the Spliterator, though it can't really be split anymore in this implementation.
Here's an untested implementation of takeWhile on a Spliterator:
sta...