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I have one file named "test-file". It has just two following lines (one line with # sign in the front and second line with same content but without hash):
#contents of line
contents of line
I want to update/replace the contents of second line by using sed command. I know its simple syntax for example:
sed -i 's/.*contents of line.*/updated contents/' test-file
but the above command is replacing both of the lines whereas I don't want to update the first line with # sign in the front.
try
sed 's/^[^#]*contents of line.*/updated contents/' test-file
or with the start of line anchor ^, and you know that line start with content ..., you could do:
sed 's/^contents of line.*/updated contents/' test-file
If you know which line you are going to update, you can change directly with its address line number like.
sed '2s/.*/updated content/' test-file
add -i when you were happy with the result.
You could do the edit the following way:
sed -e '/^#/!s/.*/UPDATED_CONTENTS/' input-file.txt
or
sed -e '/^#/!c\
UPDATED_CONTENTS' input-file.txt
this is to read as: for any line that does not begin with a # , change that whole line to what is specified.
And in case you are concerned that the octothorpe can be preceded by blanks, then tweak the regex to /^[[:blank:]]*#/ while keeping the rest exactly as is.
