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up vote 3 down vote favorite

In the canonical How can I replace a string in a file(s)? in 3. Replace only if the string is found in a certain context, I'm trying to implement the replace of a pipe with white spaces in file with structure like this:

12/12/2000|23:16:03|Shell Sc|8332|START|TEXT|WITH|SPACES|-|[END]|[Something else]

I need it like this:

12/12/2000|23:16:03|Shell Sc|8332|START TEXT WITH SPACES -|[END]|[Something else]

The code:

echo "12/12/2000|23:16:03|Shell Sc|8332|START|TEXT|WITH|SPACES|-|[END]|[Something else]" | \
 sed 's/\(START.*\)\|/ \1/g'

Any ideas ?

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up vote 5 down vote accepted

The problem with your command is that even with the g flag set, a particular portion of the text to be matched can only be included in a single match. Since .* is greedy, you will only end up removing the final pipe character. Not to mention your space in the replacement text is in the wrong place.

You could do this with a repeated s command in a loop, running until it doesn't match anything. Like so:

sed -e ':looplabel' -e 's/\(START.*\)|\(.*|\[END\)/\1 \2/;t looplabel'

Or, using a shorter loop label:

sed -e ':t' -e 's/\(START.*\)|\(.*|\[END\)/\1 \2/;tt'
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up vote 1 down vote

In this particular case, all the | you want replaced with spaces come immediately after a capital letter and immediately before a capital letter or a -. You can therefore use lookarounds:

$ perl -ple 's/(?<=[A-Z])\|(?=[A-Z-])/ /g' file
12/12/2000|23:16:03|Shell Sc|8332|START TEXT WITH SPACES -|[END]|[Something else]
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