For cycles

for variable [in word]; do
    command-list
done

Example: Counting files

for i in *.jpg; do
    j=`expr $j + 1`
done
echo $j

• expr is executed in a subshell --> expensive
• if there is no jpg-file, the string "*.jpg" is counted

for i in *.jpg; do
    test -f "$i" && echo
done | wc -l

• Note the quotes around the argument: $i could contain blanks, newlines etc.