tr -dc '[:graph:]' < /dev/urandom | tr -d \''\\'\` | head -c 1G > test.txt

time cat test.txt

real    1m4.362s
user    0m0.017s
sys     0m6.407s

real    18m33.085s
user    0m0.024s
sys     0m10.896s

real    0m17.997s
user    0m0.004s
sys     0m4.674s