#!/bin/bash
for file in *.c; do
    name=${file/%.c/}.d
    if [ -e ${name} ]; then
        echo ${name}
    fi
done

------解决方案--------------------
Perl code
#!/bin/bash
for i in *.c; do
    name=${i/.c/.d}
    if [ -e ${name} ]; then
        echo ${name}
    fi
done