问题
I want to do a substitution based on a wildcard. For example, change all "tenure" to "disposition" only if the word "tenure" comes after an '=' sign. Basically a regex that would match this =.*tenure
The sed command that I have so for this is:
sed 's/=.*tenure/=.*disposition/g' file.txt
However, if I pass this to a file containing:
blah blah blah = change "tenure" to "disposition"
I get
blah blah blah =.*disposition" to "disposition"
instead of:
blah blah blah = change "disposition" to "disposition"
How do I do the substitution such that the wildcard in the regex won't be part of the destination file?
回答1:
You need to use a capturing group to capture the text that appears between your equals sign and "tenure".
So
sed 's/=\(.*\)tenure/=\1disposition/g'
Note the use of \1 to reference and use the group you captured.
So in
echo 'blah blah blah = change "tenure" to "disposition"' | sed 's/=\(.*\)tenure/=\1disposition/g'
we get
blah blah blah = change "disposition" to "disposition".
See Regex grouping.
回答2:
sed 's/\(=.*\)tenure/\1disposition/g' file.txt
回答3:
You need to save matched characters between the = and the tenure to add them to the output:
sed 's/=(.*)tenure/=\1disposition/g' file.txt
Also, you should add the -i option to sed if you want to edit the file inplace (do the modifications to the file itself).
回答4:
You have to use backreference in sed. Use it like this:
sed 's/\(=.*\)tenure/\1disposition/g'
来源：https://stackoverflow.com/questions/6258643/sed-wildcard-substitution