Remove the lines starting with a character in shell, but preserve the negative values

Question

I have dataset as:

file.txt
de
fds
fds
a
sa
 -1
 2
 -3
 1
}

I would like to delete all the lines starting with characters or special characters, but preserve the negative values. So my outfile is:

out.txt
-1
2
-3
1

This question is related to one of my earlier questions Remove the lines starting with a character in shell with which I can remove all lines starting with a character including negative sign.

I need to modify my code.

my code:

grep -E "^[0-9].*" file.txt

sat · Accepted Answer · 2017-07-10T08:35:14.517

1

You can try like this:

grep '^ *[-+]\?[0-9]\+' file.txt > out.txt

(Or)

grep -E '^ *[-+]?[0-9]+' file.txt > out.txt

edited Jul 10 '17 at 08:35

answered Jul 10 '17 at 08:15

sat

Thank you, but I am sorry that I have space before the numbers. So it is removing all the values... I have modified my question – Kay Jul 10 '17 at 08:26
@Kay, Updated answer. – sat Jul 10 '17 at 08:35

CWLiu · Answer 2 · 2017-07-10T08:38:13.523

1

$ grep -E '^[-| ][0-9]' file.txt > out
$ cat out
-1
 2
-3
 1

edited Jul 10 '17 at 08:38

answered Jul 10 '17 at 08:27

CWLiu

2 Answers2