advanced sed print + replace

Question

I am interested if there's a more elegant solution to the one posted below.

[]$ find ./abc -type f -exec sed -n 's/test/best/pg' {} + ; find ./abc -type f -exec sed -i 's/test/best/g' {} +

The first find sed command prints all found patterns to console. The second find sed command actually substitutes the patterns within file.

The problems I have encountered:

sed -n -i (cannot have multiple command line modifier/arguments) -? someone confirm?
sed does not have a native modifier to print results prior to substitution -? had trouble finding a solution, maybe it exists, and the command can be modified (i.e. below will output nothing, and substitute behind your back!).
```
find ./abc -type f -exec sed -i 's/test/best/pg' {} +  
```

Maybe `find [...] -exec grep test {}; sed -i 's/test/best/g' {} \;`? — DopeGhoti, Dec 02 '15 at 21:48
thanks @don_crissti I'm reading that article and haven't found a good solution I'm looking for. — MaestroCookies, Dec 02 '15 at 21:51
@DopeGhoti, something more elegant, i.e. single command as opposed to using 2 commands. — MaestroCookies, Dec 02 '15 at 21:53
That'll be tough, as by design `sed` modifies one stream of input and gives one stream of output; I don't think there's any way to have it take one input and give two outputs. — DopeGhoti, Dec 02 '15 at 21:55

score 2 · Accepted Answer · answered Dec 02 '15 at 22:27

2

Well, you don't need to have two separate find commands:

find abc -type f -exec sed -n 's/test/best/pg' {} + -exec sed -i 's/test/best/g' {} +

... and you don't need the ./ in front of abc.

answered Dec 02 '15 at 22:27

Because that doesn't work. It's the worst of both worlds — it doesn't print anything, and it deletes all the lines in the file that don't match `test`. – G-Man Says 'Reinstate Monica' Dec 02 '15 at 23:32
Oh, god. That's brainless enough I'm just going to delete it. Here: `sed -ni '/test/w /dev/tty s//best/g; p'` (w/ a newline after `tty`) – jthill Dec 02 '15 at 23:40
Note that jthill edited his/her comment since I posted my first response; the first version was `sed -ni 's/test/best/pg' \{} +`. The revised version, `sed -ni '/test/{p;s//best/g}' \{} +`, is even worse: it still deletes all the lines in the file that don't match `test`, but *it doesn't even do the requested substitution on the lines that do!* – G-Man Says 'Reinstate Monica' Dec 02 '15 at 23:41
`sed -ni '/test/w /dev/tty s//best/g; p'` doesn't work either. If you think you have an answer, you should *post an answer* rather than critiquing a correct answer; comments are not good for multi-line text. If you meant to have a newline rather than a space after `/dev/tty`, it ***still doesn't work*** (suggestion: *try* commands before you post them) but is coming close to answers that were posted to [How to report “sed” in-place changes](http://unix.stackexchange.com/a/200576/80216) six months ago. – G-Man Says 'Reinstate Monica' Dec 02 '15 at 23:50
You're right, of course. Started out brainless, continued that way. My apologies. – jthill Dec 02 '15 at 23:57

score 1 · Answer 2 · answered Dec 03 '15 at 00:12

If you're on GNU/anything you can

find abc -type f -exec sed -i 's/test/best/gw /dev/fd/2' {} +

but in your text you mentioned wanting to print results prior to substitution, not sure what "results" means there but

find abc -type f -exec sed -i '/test/w /dev/fd/2
                               s//best/g' {} +

prints the lines that will change prior to substitution.

2 Answers2