air
smell
hand
dude
road
cat

air,4,21,01,13,3,2
smell,21,4,2,5,6
dude,1,31,42,1
road,1,4,2,1,4
cat,1,5,6,3,1
hand,1,4,2,1,6
mouse,1,3,5,6,2

air,4,21,01,13,3,2
smell,21,4,2,5,6
hand,1,4,2,1,6
dude,1,31,42,1
road,1,4,2,1,4
cat,1,5,6,3,1

awk -F, 'FNR==NR {a[$1]; next}; $1 in a' file1 file2

gawk -F, '
    FNR==NR {a[NR]=$1; next};
    {b[$1]=$0}
    END{for (i in a) if (a[i] in b) print b[a[i]]}
' file1 file2

awk -F, 'FNR==NR {a[$1]=$0; next}; $1 in a {print a[$1]}' file2 file1

join -t, -1 2 -2 1 <(nl -s, -ba -nrz file1 | sort -t, -k2)
<(sort -t, -k1 file2) | sort -t, -k2 | cut -d, -f1,3-

air,000001,4,21,01,13,3,2
cat,000006,1,5,6,3,1
dude,000004,1,31,42,1
hand,000003,1,4,2,1,6
road,000005,1,4,2,1,4
smell,000002,21,4,2,5,6

air,4,21,01,13,3,2
smell,21,4,2,5,6
hand,1,4,2,1,6
dude,1,31,42,1
road,1,4,2,1,4
cat,1,5,6,3,1

grep -f file1 file2