# xev
# Print contents of X events

# Start xev(1) and show only the relevant parts.
xev | awk -F'[ )]+' '
    /^KeyPress/ {
        a[NR+2]
    }
    NR in a {
        printf "%-3s %s\n", $5, $8
    }
'
# Alternative approach to showing keycodes.
#
# Note that the use of `<(xev)` is process substitution, which is unavailable
# in the Bourne Shell and its standard derivatives, nor is it available in Bash
# with its own POSIX mode enabled.
awk '
    /^KeyPress/ {
        A[NR+2]
    }
    NR in A {
        B=substr($7, 0, length($7) - 2)
        printf("%3d %s\n", $4, B)
    }
' <(xev)