How to write in awk to remove lines starting with "#" and then process the file:
This is not working:
cat file|awk '{if ($0 ~ /^#/) $0="";print NF>0}'
When I just give
cat file|awk '{if ($0 ~ /^#/) $0="";print }'
it prints the blank lines . I don't wnat the blank lines along with the data lines.
Thanks,
Why don't you simply do:
awk '$0 !~ /^#/ && NF' file
If you want to perform any action:
awk '$0 !~ /^#/ && NF{ action here }' file
Try:
awk '!/^#/' file
grep -v '^#' file
To suppress printing of blank lines and remove lines starting with #
awk '!/^#|^$/' file
PS: no need to cat data to awk
Thanks Yoda,
I was looking for something like this
awk '$0 !~ /^#/ && NF{ action here }' file
, it worked great, but it is also removing exiting empty lines, but that is fine in this case,
Scrutinizer ,
I dont wanted to use grep -v, as wanted to pass in one awk statement. Thanks again...
Jotne, This worked great as well,
awk '!/^#|^$/' file
,
But surprised it leaves only one blank line on the data file, after it removed all starting hash and blank lines.
Thanks all. .
You may have blanks or tabs in the remaining line.
Try this:
awk 'NF && !/#/ {action}' file
If you don't want to remove existing empty lines, then I guess what Scrutinizer posted is the right approach.
Just add your action part to it:
awk '!/^#/ { action here } ' file
grep '^[^#]' file
awk '/^[^#]/ {print}' file
removes empty lines, but leaves lines with a blank character.
MadeInGermany ,
Thanks this is also a nice code, seems inside [ ] the caret is doing negetion for #.
But couldn''t get how the empty lines are getting removed.
awk '/^[^#]/ {print}' file
Is that means print lines starting with something , but not hash and empty lines.
Thanks for the post.
It greps the lines with a first character that is not a #
But a blank line does not start with # , so why does it remove it?
awk '/^[^#]/ {print}' file
It prints lines that start with a character that is not #. A blank line does not start with a character. So a blank line is not printed, so the blank line is removed (as well as a line starting with #).
-------------------------------
An alternative way, maybe easier to understand, using grep:
grep -v -e '^#' -e '^$' file
This means "print all lines except those that start with # or that are blank".
Ok, now I understand, thanks.
So ii there are lines that do contain spaces or tabs it will not work. awk '/^[^#]/ {print}' file
This would. awk 'NF && !/#/ {action}' file
awk 'NF && !/#/ {action}' file
That would not work. It has two problems.
First, it would need to be !/^#/ to mean "do not act on lines that start with #".
Second, the idea was to act on lines that have a space character. But NF is 0 if just a space character, just as NF is 0 if the line is totally blank. So it would not act on the lines with spaces.
-----------------------
Look at the test input below, where the expected output is to NOT print first two lines (empty, start with #), and do print last three lines, and compare the results from the three ways:
$ cat -e input
# X$
$
X #$
$
string 1-99-string 2$
$ awk 'NF && !/#/ {print}' input
string 1-99-string 2
$ awk '/^[^#]/ {print}' input | cat -e
X #$
$
string 1-99-string 2$
$ grep -v -e '^#' -e '^$' input | cat -e
X #$
$
string 1-99-string 2$
Indeed, with hand-edited files in particular there are often empty lines that are not entirely empty and that contains some form of spacing. Also, lines with only comment can be indented for clarity and therefore do not always start at the first position on the line. So in general I would tend to use:
awk '$1~/^[^#]/' file
To exclude empty lines and lines with only comment that may contain leading spacing and
awk '$1!~/^#/' file
To only exclude lines with only comment and that may contain leading spacing and
awk NF
to only exclude empty lines that that may contain tabs or spaces.
Also hanson44 & Scrutinizer, thanks ..,
Scrutinizer,
Thanks much , this worked... to remove empty lines, and comments( starting with # ) and seems to be fixed earlier issues, It worked even the file has a space and then it has the comment starting with #.
awk '$1~/^[^#]/' file
Thanks.