replacing and adding at the end of lines with one line sed command

Question

I have a line as follows

 // Testing this

I am trying to use a sed command to replace the // with a /* (sentence or word in between) */ on each line.

so it should look something like this

/* Testing this */

The first part is easy with calling

sed 's#//#/*#'

however, with the second part, I tried this solution

Appending word at the end of line with sed [duplicate]

I tried with -e which gave me an error of 'unterminated s command'. Then, I tried with a semi colon to make it one so it was something along the lines of

's#//#/*#;#//#s#/$#*/#'

but all that seems to do is the first part (replacing // with /*)and not the second (putting a */ at the end of the same line).

What am I not doing correctly? Any pointers would be appreciated.

Answer 1

How about

$ cat testfile
// Testing this
foobar
$ sed 'sx//\(.*\)x/*\1 */x' testfile
/* Testing this */
foobar
$

• sx// : search for lines containing //
• \(.*\)x : place the remaining part of the line into capture group 1
• /*\1 */x : replace the remaining part of the line with /* (start of comment, C-style) followed by the contents of the capture group 1 (referenced as \1), followed by */ (end of comment, C-style)

Answer 2

Another approach: make the search and replace conditional on the comment being matched at all:

sed '\!//! {s!!/*!; s!$! */!}' file

That reads:

• if the line contains the pattern //, then
  • replace the matched text with /*
  • and then replace the empty string at end of line with */