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I've encountered the following problem: I need to add space at certain position in each line, to transform data from

ATOM      1 HT1 GLY     5      10.346  30.927 130.252  0.00  0.00

to (by adding space in 12th column)

ATOM      1  HT1 GLY     5      10.346  30.927 130.252  0.00  0.00

Now I've managed to achieve it with:

cat $INFILE | cut -c-11 > $INFILE.1
cat $INFILE | cut -c12- > $INFILE.2
paste -d ' ' $INFILE.1 $INFILE.2 > $INFILE

But may be there is more elegant solution, without using temporary files?

Thanks in advance.

share|improve this question
up vote 3 down vote accepted

You can certainly do this with sed but I know perl better ...

  perl -p -i -e 's/^(.{12})/$1 /' $INFILE


  sed -i -e 's/^.\{12\}/& /' $INFILE
share|improve this answer
sed also knows about {}, but needs escaping: sed -i 's/.\{12\}/& /' $INFILE` works. – Daniel Andersson May 8 '12 at 14:22

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