Join 2 files by common column header (without awk/sed) - linux

Question

Basically I want to get all records from file2, but filter out columns whose header doesn't appear in file1
Example:
file1
Name Location
file2
Name Phone_Number Location Email
Jim 032131 xyz xyz#qqq.com
Tim 037903 zzz zzz#qqq.com
Pimp 039141 xxz xxz#qqq.com
Output
Name Location
Jim xyz
Tim zzz
Pimp xxz
Is there a way to do this without awk or sed, but still using coreutils tools? I've tried doing it with join, but couldn't get it working.

Answer 1

ALL_COLUMNS=$(head -n1 file2)
for COLUMN in $(head -n1 file1); do
JOIN_FORMAT+="2.$(( $(echo ${ALL_COLUMNS%%$COLUMN*} | wc -w)+1 )),"
done
join -a2 -o ${JOIN_FORMAT%?} /dev/null file2
Explanation:
ALL_COLUMNS=$(head -n1 file2)
It saves all the column names to filter next
for COLUMN in $(head -n1 file1); do
JOIN_FORMAT+="2.$(( $(echo ${ALL_COLUMNS%%$COLUMN*} | wc -w)+1 )),"
done
For every column in file1, we look for the position of the one with the same name in file2 and append it to JOIN_FORMAT in the way of "2.<number_of_column>,"
join -a2 -o ${JOIN_FORMAT%?} /dev/null file2
Once we have the option string complete (2.1,2.3,), we pass it to join removing the last ,.
join prints the unpairable lines from the second file provided (-a2 -> file2), but only the columns specified in the -o option.

Answer 2

Not very efficient, but works for your example:
#!/bin/bash
read -r -a cols < file1
echo "${cols[#]}"
read -r -a header < <(head -n1 file2)
keep=()
for (( i=0; i<${#header}; i++ )) ; do
for c in "${cols[#]}" ; do
if [[ ${header[i]} == "$c" ]] ; then
keep+=($i)
fi
done
done
while read -r -a data ; do
for idx in ${keep[#]} ; do
printf '%s ' "${data[idx]}"
done
printf '\n'
done < <(tail -n+2 file2)
Tools used: head and tail. They aren't essential, though. And bash, of course.