AWK scripting :How to remove Field separator using awk - shell

Question

Need the following output
ONGC044
ONGC043
ONGC042
ONGC041
ONGC046
ONGC047
from this input
Medium Label Medium ID Free Blocks
===============================================================================
[ONGC044] ECCPRDDB_FS_43 ac100076:4aed9b39:44f0:0001 195311616
[ONGC043] ECCPRDDB_FS_42 ac100076:4aed9b1d:44e8:0001 195311616
[ONGC042] ECCPRDDB_FS_41 ac100076:4aed9af4:4469:0001 195311616
[ONGC041] ECCPRDDB_FS_40 ac100076:4aed9ad3:445e:0001 195311616
[ONGC046] ECCPRDDB_FS_44 ac100076:4aedd04a:68c6:0001 195311616
[ONGC047] ECCPRDDB_FS_45 ac100076:4aedd4a0:6bf5:0001 195311616

Answer 1

awk -F"[][]" 'NR>2{print $2}' file

Answer 2

I think what you want is:
awk '/^\[.*\]/ {print substr($1,2,7)}' < ~/tmp/awk_test/file
This assumes that your first field is exactly 9 (7 of them are the ones you want) characters each time. If this is not the case, then use the following instead to strip off of the [ and the ] from the first field:
awk '/^\[.*\]/ {gsub(/[\[\]]/,"",$1); print $1 }' < ~/tmp/awk_test/file

Answer 3

If the data is really that uniform, a very simple pipe to:
cut -b 2-8
will do it for you.
(Oh, apart from the first two lines; get rid of them with grep ^\[ in your pipeline, if you need to)

Answer 4

Here's a solution which only involves awk. The idea is to let awk parse the desired column and remove the undesired square brackets from this token. The only "trick" is to "escape" the [ character lest it is understood as an opening re set. (We could also use substr instead since the brackets are expected as the first and last characters)
{
#skip the column header lines
if (NR < 3)
next;
# $1 is almost what we want: [xxxx]
# ==> just remove the square brackets
sub("[[]", "", $1);
sub("]", "", $1);
print $1;
}