如何使用bash附加到文件中包含匹配模式的行的开头和结尾？

Question

I need to add a <!-- to the beginning of a line and --> to the end of a line for each line in a xml file if a certain string is present. so, for example, if BlueCard is the string I want to match and the file looks like this currently:

RedCard
BlueCard
GreenCard

I want the new file to look like:

RedCard
<!--BlueCard-->
GreenCard

How can this be done?

Answer 1

与sed：

sed 's/.*BlueCard.*/<!--&-->/' file

Answer 2

You can also match pattern and then apply substitute( s ) for all lines that matches.

sed '/BlueCard/ s/.*/<!--&-->/' test

• & Here it selects everything that is matched by .*

Answer 3

try in awk too once.

awk '/BlueCard/{print "<!--" $0 "-->";next} 1'  Input_file

So looking for string BlueCard in a line if it finds it then print the comments with that line, using next will not skip all further statements. using 1 will print everything apart from line having BlueCard as it is already taken care by the condition itself.

Solution 2nd: Using sub utility of awk here.

awk '{sub(/BlueCard/,"<!--&-->")} 1'   Input_file

Simply substituting string BlueCard here with the comments and printing everything then.