redirect demo

bash-4.2$ time bash -c 'for i in *; do wc -l "$i" > /dev/null; done'
real    0m53.862s
user    0m6.332s
sys     0m34.620s

bash-4.2$ time bash -c 'for i in *; do wc -l "$i"; done > /dev/null'
real    0m50.752s
user    0m7.815s
sys     0m34.841s

bash-4.2$ time bash -c 'for i in *; do echo "$i" > /dev/null; done'
real    0m0.622s
user    0m0.469s
sys     0m0.145s

bash-4.2$ time bash -c 'for i in *; do echo "$i"; done > /dev/null'
real    0m0.434s
user    0m0.408s
sys     0m0.023s

bash-4.2$ time bash -c 'for i in *; do :; done'
real    0m0.330s
user    0m0.309s
sys     0m0.018s



bash-4.2$ time dash -c 'for i in *; do wc -l "$i" > /dev/null; done'
real    0m38.478s
user    0m8.730s
sys     0m26.164s

bash-4.2$ time dash -c 'for i in *; do wc -l "$i"; done > /dev/null'
real    0m34.807s
user    0m6.026s
sys     0m18.429s

bash-4.2$ time dash -c 'for i in *; do echo "$i" > /dev/null; done'
real    0m0.329s
user    0m0.141s
sys     0m0.180s

bash-4.2$ time dash -c 'for i in *; do echo "$i"; done > /dev/null'
real    0m0.114s
user    0m0.090s
sys     0m0.023s

bash-4.2$ time dash -c 'for i in *; do :; done'
real    0m0.065s
user    0m0.047s
sys     0m0.017s