使用sed仅查找和替换字符串中的数字和第3个数字

Question

In a huge file i have port numbers like

"port": "7733",
"port": "7734",
"port": "7631",
"port": "7833",
"port": "7835",
"port": "7335",
"port": "9834",

I just have to replace(only 3rd number) 3 with 5 using sed. the intended result should be like

"port": "7753",
"port": "7754",
"port": "7651",
"port": "7853",
"port": "7855",
"port": "7355",
"port": "9854",

I have tried

sed -E 's/[0-9][0-9]3[0-9]+/[0-9][0-9]5[0-9]/g'

but this will replace all numbers to [0-9][0-9]5[0-9].

Please let me know how can we achieve using sed

Answer 1

sed allows you to save the text that matched a regex as a group to be used later. This solution saves two groups: the numbers before the 3 and the numbers after. The replacement text thus consists of the first group, denoted \\1 , the number 5 , and the second group, denoted \\2 . Thus:

$ sed -E 's/([0-9][0-9])3([0-9]+)/\15\2/g' file
"port": "7753",
"port": "7754",
"port": "7651",
"port": "7853",
"port": "7855",
"port": "7355",
"port": "9854",

Answer 2

If you data contains 4 digit ports then using awk you can just split the field and add 20 to it:

$ awk 'BEGIN{FS=OFS="\""}{$4+=20}1' file
"port": "7753",
"port": "7754",
"port": "7651",
"port": "7853",
"port": "7855",
"port": "7355",
"port": "9854",

Once the output looks good, you can re-direct to another file. Alternatively if you are using GNU awk v4.1 or later you can make changes in place by doing:

awk -i inplace 'BEGIN{FS=OFS="\""}{$4+=20}1' file