awk to remove 5th column from N column with fixed delimiter - awk

Question

I have file with Nth columns
I want to remove the 5th column from last of Nth columns
Delimiter is "|"
I tested with simple example as shown below:
bash-3.2$ echo "1|2|3|4|5|6|7|8" | nawk -F\| '{print $(NF-4)}'
4
Expecting result:
1|2|3|5|6|7|8
How should I change my command to get the desired output?

Answer 1

If I understand you correctly, you want to use something like this:
sed -E 's/\|[^|]*((\|[^|]*){4})$/\1/'
This matches a pipe character \| followed by any number of non-pipe characters [^|]*, then captures 4 more of the same pattern ((\|[^|]*){4}). The $ at the end matches the end of the line. The first part of the match (i.e. the fifth field from the end) is dropped.
Testing it out:
$ sed -E 's/\|[^|]*((\|[^|]*){4})$/\1/' <<<"1|2|3|4|5|6|7"
1|2|4|5|6|7
You could achieve the same thing using GNU awk with gensub but I think that sed is the right tool for the job in this case.
If your version of sed doesn't support extended regex syntax with -E, you can modify it slightly:
sed 's/|[^|]*\(\(|[^|]*\)\{4\}\)$/\1/'
In basic mode, pipes are interpreted literally but parentheses for capture groups and curly brcneed to be escaped.

Answer 2

AWK is your friend :
Sample Input
A|B|C|D|E|F|G|H|I
A|B|C|D|E|F|G|H|I|A
A|B|C|D|E|F|G|H|I|F|E|D|O|R|Q|U|I
A|B|C|D|E|F|G|H|I|E|O|Q
A|B|C|D|E|F|G|H|I|X
A|B|C|D|E|F|G|H|I|J|K|L
Script
awk 'BEGIN{FS="|";OFS="|"}
{$(NF-5)="";sub(/\|\|/,"|");print}' file
Sample Output
A|B|C|E|F|G|H|I
A|B|C|D|F|G|H|I|A
A|B|C|D|E|F|G|H|I|F|E|O|R|Q|U|I
A|B|C|D|E|F|H|I|E|O|Q
A|B|C|D|F|G|H|I|X
A|B|C|D|E|F|H|I|J|K|L
What we did here
As you are aware awk's has special variables to store each field in the record, which ranges from $1,$2 upto $(NF)
To exclude the 5th from the last column is as simple as
Emptying the colume ie $(NF-5)=""
Removing from the record, the consecutive | formed by the above step ie do sub(/\|\|/,"|")

Answer 3

another alternative, using #sjsam's input file
$ rev file | cut -d'|' --complement -f6 | rev
A|B|C|E|F|G|H|I
A|B|C|D|F|G|H|I|A
A|B|C|D|E|F|G|H|I|F|E|O|R|Q|U|I
A|B|C|D|E|F|H|I|E|O|Q
A|B|C|D|F|G|H|I|X
A|B|C|D|E|F|H|I|J|K|L
not sure you want the 5'th from the last or 6th. But it's easy to adjust.

Answer 4

Thanks for the help and guidance.
Below is what I tested:
bash-3.2$ echo "1|2|3|4|5|6|7|8|9" | nawk 'BEGIN{FS="|";OFS="|"} {$(NF-4)="!";print}' | sed 's/|!//'
Output: 1|2|3|4|6|7|8|9
Further tested on the file that I have extracted from system and so it worked fine.