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Math Forum » Discussions » Software » comp.soft-sys.math.mathematica

Topic: Obtaining Random LIne from A file
Replies: 9   Last Post: Feb 21, 2013 5:46 AM

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Ramiro Barrantes-Reynolds

Posts: 9
Registered: 10/14/07
Obtaining Random LIne from A file
Posted: Feb 16, 2013 1:07 AM
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Hello,

I would like to get a random line from a file, I know this can be done
with Mathematica but I am playing with using sed to see if it goes
faster, say I want to get line 1000

In mathematica it would be:

<<"! sed -n p1000 filename.txt"

However, I am trying to put the filename as a variable, say

filename="hugefile.txt"

cmd="! sed -n p1000 "<>filename
<<cmd

does not work.

How can I do this?

Lastly, I am getting a randomline using mathematica doing:

getRandomLine[file_, n_] :=
Block[{i = RandomInteger[{1, n}], str = OpenRead[file], res},
Skip[str, "String", i];
res = Read[str, Expression];
Close[str];
res[[2]]
]

However, it is very slow so I was going to try with sed.Any suggestions?

Thanks in advance,
Ramiro

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