Adding double quotes around non-numeric columns by awk - linux

Question

I have a file like this;
2018-01-02;1.5;abcd;111
2018-01-04;2.75;efgh;222
2018-01-07;5.25;lmno;333
2018-01-09;1.25;prs;444
I'd like to add double ticks to non-numeric columns, so the new file should look like;
"2018-01-02";1.5;"abcd";111
"2018-01-04";2.75;"efgh";222
"2018-01-07";5.25;"lmno";333
"2018-01-09";1.25;"prs";444
I tried this so far, know that this is not the correct way
head myfile.csv -n 4 | awk 'BEGIN{FS=OFS=";"} {gsub($1,echo $1 ,$1)} 1' | awk 'BEGIN{FS=OFS=";"} {gsub($3,echo "\"" $3 "\"",$3)} 1'
Thanks in advance.

Answer 1

You may use this awk that sets ; as input/output delimiter and then wraps each field with "s if that field is non-numeric:
awk '
BEGIN {
FS = OFS = ";"
}
{
for (i=1; i<=NF; ++i)
$i = ($i+0 == $i ? $i : "\"" $i "\"")
} 1' file
"2018-01-02";1.5;"abcd";111
"2018-01-04";2.75;"efgh";222
"2018-01-07";5.25;"lmno";333
"2018-01-09";1.25;"prs";444
Alternative gnu-awk solution:
awk -v RS='[;\n]' '$0+0 != $0 {$0 = "\"" $0 "\""} {ORS=RT} 1' file

Answer 2

Using GNU awk and typeof(): Fields - - that are numeric strings have the strnum attribute. Otherwise, they have the string attribute.1
$ gawk 'BEGIN {
FS=OFS=";"
}
{
for(i=1;i<=NF;i++)
if(typeof($i)=="string")
$i=sprintf("\"%s\"",$i)
}1' file
Some output:
"2018-01-02";1.5;"abcd";111
- -
Edit:
If some the fields are already quoted:
$ gawk 'BEGIN {
FS=OFS=";"
}
{
for(i=1;i<=NF;i++)
if(typeof($i)=="string")
gsub(/^"?|"?$/,"\"",$i)
}1' <<< string,123,"quoted string"
Output:
"string",123,"quoted string"

Answer 3

Further enhancing upon anubhava's solution (including handling fields already double-quoted :
gawk -e 'sub(".+",$-_==+$-_?"&":(_)"&"_\
)^gsub((_)_, _)^(ORS = RT)' RS='[;\n]' \_='\42'
"2018-01-02";1.5;"abcd";111
"2018-01-04";2.75;"efgh";222
"2018-01-07";5.25;"lmno";333
"2018-01-09";1.25;"prs";444
"2018-01-09";1.25;"prs";111111111111111111112222222222
222222223333333333333333333333
333344444444444444444499999999
999991111111111111111111122222
222222222222233333333333333333
333333333444444444444444444999
999999999991111111111111111111
122222222222222222233333333333
333333333333333444444444444444
444999999999999991111111111111
111111122222222222222222233333
333333333333333333333444444444
444444444999999999999991111111
111111111111122222222222222222
233333333333333333333333333444
444444444444444999999999999991
111111111111111111122222222222
222222233333333333333333333333
333444444444444444444999999999
999991111111111111111111122222
222222222222233333333333333333
333333333444444444444444444999
999999999999