How to delete text between two matching strings inclusive (only first occurence) that is at the very beginning of the file?

Question

I am trying to remove the text between /* and */ that is at the beginning of the file. There can be white spaces or new lines (\n) before or in-between /* and */.

I tried following but doesn't work when space or new lines are there.

sed '/^\/\*/,/\*\//d' file

Sample file:

   /*******
delete
bla

***
  */
/* do not */
print "hi"
/*******
dont delete
****/

Expected output:

/* do not */
print "hi"
/*******
dont delete
****/

Does this answer your question? [Regex to remove multi line comments](https://stackoverflow.com/questions/2458785/regex-to-remove-multi-line-comments) — Bren, Jul 10 '20 at 23:43
It doesn't help. Tried on my file, but it doesn't delete anything. — Sweety, Jul 10 '20 at 23:46
Please, avoid changing rules when you have 2 answers https://stackoverflow.com/posts/62843678/revisions — Gilles Quénot, Jul 11 '20 at 00:11
if the first line is `X /* blah...`, is `X` supposed to be removed from output? What about the spaces immediately following `X` ? — M. Nejat Aydin, Jul 11 '20 at 01:52
What should the output be if the first line of the input file is `print "/* uh-oh */"`? You need a parser for whatever language your input file is written in to do this job robustly. — Ed Morton, Jul 11 '20 at 03:15

score 1 · Answer 1 · answered Jul 10 '20 at 23:51

1

If ed is available.

printf '%s\n' '/^[[:space:]]*\//;/^[[:space:]]*\*\//d' ,p Q | ed -s file.txt

Change Q to w to edit the file.

answered Jul 10 '20 at 23:51

Jetchisel

7,493
2
19
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Ed Morton · Answer 2 · 2020-07-11T03:07:53.817

Using any awk in any shell on every UNIX box, this will produce the output you want from the input you provided:

$ awk 'f; /\*\//{f=1}' file
/* do not */
print "hi"
/*******
dont delete
****/

but consider also this more general approach:

$ cat tst.awk
{ rec = (NR>1 ? rec ORS : "") $0 }
END {
    $0 = rec

    gsub(/@/,"@A"); gsub(/{/,"@B"); gsub(/}/,"@C")
    gsub(/\/\*/,"{"); gsub(/\*\//,"}")

    sub(/^[[:space:]]*{[^}]*}[[:blank:]]*\n/,"")

    gsub(/}/,"*/"); gsub(/{/,"/*")
    gsub(/@C/,"}"); gsub(/@B/,"{"); gsub(/@A/,"@")

    print
}

.

$ awk -f tst.awk file
/* do not */
print "hi"
/*******
dont delete
****/

See https://stackoverflow.com/a/56658441/1745001 for an explanation of what those gsub()s are doing.

Gilles Quénot · Answer 3 · 2020-07-11T00:10:15.613

0

 awk 'BEGIN{f=-1} /^ *\/\*+/{f++}f' file

/* do not */
print "hi"
/*******
dont delete
****/

edited Jul 11 '20 at 00:10

answered Jul 10 '20 at 23:55

Gilles Quénot

173,512
41
224
223

Did not work for me. Do you have white space before first `/*`? – Sweety Jul 11 '20 at 00:06
Post edited accordingly – Gilles Quénot Jul 11 '20 at 00:10
Not sure why, but still doesn't work for me on the same file. – Sweety Jul 11 '20 at 00:21
Works even with 'mawk', with exactly the source file you provide. Are you on windows ? – Gilles Quénot Jul 11 '20 at 00:36

How to delete text between two matching strings inclusive (only first occurence) that is at the very beginning of the file?

3 Answers3