Unix Regex: No line longer than 70 characters in a text file

Question

I need to use a regex in unix to make sure no line in a text document is over 70 characters, and I just cannot find the right expression. I've been trying:

sed "s/\(^.{70}\)/\1\n\r/g" firstMondayNoParas2.txt > firstMondayLined.txt

This expression isn't working though. What am I missing?

Answer 1

You need to escape also the curly braces.

sed "s/^\(.\{70\}\)/\1\n\r/"

Example:

$ echo 'foobar' | sed 's/^\(.\{3\}\)/\1\n\r/'
foo
bar

$ echo 'foobar' | sed 's/^.\{3\}/&\n\r/'
foo
bar

If you want to cut for every 70 chars then you may try like this,

sed 's/.\{3\}/&\n/g' file

Example:

$ echo 'foobarbuzbu' | sed 's/.\{3\}/&\n/g'
foo
bar
buz
bu

You could use perl also.

$ echo 'foobarbuz' | perl -pe 's/(.{3})(?!$)/\1\n/g'
foo
bar
buz

(.{3})(?!$) would capture each three chars but not the one which was present at the last. So this won't add a extra new line character at the last if your input has chars multiple of 3. To do an in-place edit, you must need to add -i parameter like

perl -i -pe 's/(.{70})(?!$)/\1\n/g' file