Date: Feb 15, 2013 1:56 AM
Author: Ramiro
Subject: Executing external command with parameters

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.

Thanks in advance,
Ramiro