gsub with awk on a file by name - bash

Question

I'm trying to learn how to use awk with gsub for a particular field, but passing the name, not the number of the column on this data:
especievalida,nom059
Rhizophora mangle,Amenazada (A)
Avicennia germinans,Amenazada (A)
Laguncularia racemosa,Amenazada (A)
Cedrela odorata,Sujeta a protección especial (Pr)
Litsea glaucescens,En peligro de extinción (P)
Conocarpus erectus,Amenazada (A)
Magnolia schiedeana,Amenazada (A)
Carpinus caroliniana,Amenazada (A)
Ostrya virginiana,Sujeta a protección especial (Pr)
I tried
awk -F, -v OFS="," '{gsub("\\(.*\\)", "", $2 ) ; print $0}'
removes everything between parentheses on the second ($2) column; but I'd really like to be able to pass "nom059" to the expression, to get the same result

Answer 1

When reading the first line of your input file (the header line) build an array (f[] below) that maps the field name to the field number. Then you can access the fields by just using their names as an index to f[] to get their numbers and then contents:
$ cat tst.awk
BEGIN {
FS = OFS = ","
}
NR==1 {
for (i=1; i<=NF; i++) {
f[$i] = i
}
}
{
gsub(/\(.*\)/,"",$(f["nom05"]))
print
}
$ awk -f tst.awk file
especievalida,nom059
Rhizophora mangle,Amenazada
Avicennia germinans,Amenazada
Laguncularia racemosa,Amenazada
Cedrela odorata,Sujeta a protección especial
Litsea glaucescens,En peligro de extinción
Conocarpus erectus,Amenazada
Magnolia schiedeana,Amenazada
Carpinus caroliniana,Amenazada
Ostrya virginiana,Sujeta a protección especial
By the way, read https://www.gnu.org/software/gawk/manual/gawk.html#Computed-Regexps for why you should be using gsub(/.../ (a constant or literal regexp) instead of gsub("..." (a dynamic or computed regexp).

Answer 2

Could you please try following. I have made an awk variable named header_value where you could mention field name on which you want to use gsub.
awk -v header_value="nom059" '
BEGIN{
FS=OFS=","
}
FNR==1{
for(i=1;i<=NF;i++){
if($i==header_value){
field_value=i
}
}
print
next
}
{
gsub(/\(.*\)/, "",$field_value)
}
1
' Input_file
Explanation: Adding explanation of above code.
awk -v header_value="nom059" ' ##Starting awk program here and creating a variable named header_value whose value is set as nom059.
BEGIN{ ##Starting BEGIN section of this program here.
FS=OFS="," ##Setting FS and OFS value as comma here.
} ##Closing BEGIN section here.
FNR==1{ ##Checking condition if FNR==1, line is 1st line then do following.
for(i=1;i<=NF;i++){ ##Starting a for loop which starts from i=1 to till value of NF.
if($i==header_value){ ##checking condition if any field value is equal to variable header_value then do following.
field_value=i ##Creating variable field_value whose value is variable i value.
}
}
print ##Printing 1st line here.
next ##next will skip all further statements from here.
}
{
gsub(/\(.*\)/, "",$field_value) ##Now using gsub to Globally substituting everything between ( to ) with NULL in all lines.
}
1 ##Mentioning 1 will print edited/non-edited line.
' Input_file ##Mentioning Input_file name here.