1.mv file1 ../..
2.ln -s /lib64/libc.so /usr/lib64/lib.so
3.mkdir dic
4.free -m
free -k
5.ls -l /root | tr '/n' ' '
6.echo {1..100} | tr ' ' + | bc
7. tr 0-9 a-j < file
8.cat /etc/issue | tr a-z A-Z > /tmp/issue.out