sed filter to substitute '!' for periods and '!!' for periods at the end of lines

I want to write a sed filter that changes all periods in its 开发者_高级运维input to exclamation marks, unless the period is at the end of a line, in which case the period is replaced with 2 exclamation marks (ie. !!).

So far, this is what I have:

sed -e 's/\./\!/g' -e 's/\!\n/\!\!\n/g' input_exp

where input_exp is a file that has a few sentences written in it. The command does not work though. Is '\n' not the correct end of line character in unix/bash? Do I need an extra '\' before '\n'?

Thanks for your help.

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sed -e 's_\.$_!!_g' -e 's_\._!_g' input_exp

I've used _ instead of / for a slightly higher degree of readibility. You can also use

sed -e 's/\.$/!!/g' -e 's/\./!/g' input_exp

if you want to, of course. \n stands for newline, and is not the same as end of line.

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Use $ for 'end of line' inside the regex.