如何用新的标头和尾部字符串替换目录中所有文件的标头和尾部，但最多只能确定一个字符？

Question

I have files in a directory: ex:

file1
file2

Both files have contents that look like the below (header, body, trailer words just for reference):

header: 123xxx   xxx   value=file1id
body: blah blah blah
trailer: 123zzz   zzz   value=file1id

I want to run a linux command that will replace the header and trailer of all the files in the directory, up to "file1id", so that they look like the below:

header: 321aaa   aaa   value=file1id
body: blah blah blah
trailer: 321bbb   bbb   value=file1id

I can easily find how to replace the whole header or trailer in a file on Google, but I need the file1id in my file. I need some guidance on how to loop through files in a directory and replace the header and trailer up to a certain character in the header and trailer.

I have seen a variety of sed and awk expressions that delete and replace the header or trailer.

sed -rne 's/(value=)\s+\w+/\1 yyy/gip'

As I mentioned above, I want to run a linux command that will replace the header and trailer of all the files in the directory, up to "file1id", so that they look like the below:

header: 321aaa   aaa   value=file1id
body: blah blah blah
trailer: 321bbb   bbb   value=file1id

Answer 1

This sed example has two replace commands, one for the first line (header) and one for last line trailer (denoted by $ in the second substitution). -i option of sed edits the file in place.

sed -i '1 s/^.*value=/yoursubstitution value=/; $ s/^.*value=/yoursubstitution value=/'

output:

yoursubstitution value=file1id
body: blah blah blah
yoursubstitution value=file1id

Answer 2

You can match from the beginning of the line ( ^ ) to value=

echo 'header: 123xxx   xxx   value=file1id' | sed 's/^.*value=/header: 321aaa   aaa   value=/'
header: 321aaa   aaa   value=file1id