Here is a list of unix and linux commands that may come useful someday. If you want to learn more just search this commands to know what is their use.

A a2p | ac | alias | ar | arch | arp | as | at | awk B basename | bash | bc | bdiff | bfs | bg | biff | break | bs | bye C cal | calendar | cancel | cat | cc | cd | chdir | checkeq | checknr | chfn | chgrp | chkey | chmod | chown | chsh | cksum | clear | cls | cmp | col | comm | compress | continue | copy | cp | cpio | crontab | csh | csplit | ctags | cu | curl | cut D date | dc | df | deroff | dhclient | diff | dig | dircmp | dirname | dmesg | dos2unix | dpost | du E echo | ed | edit | egrep | elm | emacs | enable | env | eqn | ex | exit | expand | expr F fc | fg | fgrep | file | find | findsmb | finger | fmt | fold | for | foreach | fromdos | fsck | ftp
G getfacl | gprof | grep | groupadd | groupdel | groupmod | gunzip | gview | gvim | gzip H halt | hash | hashstat | head | help | history | host | hostid | hostname I id | ifconfig | ifdown | ifup | isalist J jobs | join K keylogin | kill | ksh L ld | ldd | less | lex | link | ln | lo | locate | login | logname | logout | lp | lpadmin | lpc | lpq | lpr | lprm | lpstat | ls M mach | mail | mailcompat | mailx | make | man | merge | mesg | mii-tool | mkdir | mkfs | more | mount | mt | mv N nc | neqn | netstat | newalias | newform | newgrp | nice | niscat | nischmod | nischown | nischttl | nisdefaults | nisgrep | nismatch | nispasswd | nistbladm | nmap | nohup | nroff | nslookup O on | onintr | optisa P pack | pagesize | passwd | paste | pax | pcat | perl | pg | pgrep | pico | pine | ping | pkill | poweroff | pr | priocntl | printf | ps | pvs | pwd
Q quit R rcp | reboot | red | rehash | remsh | repeat | rgview | rgvim | rlogin | rm | rmail | rmdir | rn | route | rpcinfo | rsh | rsync | rview | rvim S s2p | sag | sar | scp | script | sdiff | sed | sendmail | set | setenv | setfacl | settime | sftp | sh | shred | shutdown | sleep | slogin | smbclient | sort | spell | split | stop | stat | strip | stty | su | sudo | sysinfo | sysklogd T tabs | tac | tail | talk | tar | tbl | tcopy | tcpdump | tee | telnet | time | timex | todos | top | touch | tput | tr | traceroute | tree | troff U ul | umask | unalias | unhash | uname | uncompress | uniq | unmount | unpack | untar | until | uptime | useradd | userdel | usermod V vacation | vedit | vgrind | vi | view | vim | vipw | vmstat W w | wait | wc | wget | whereis | while | which | who | whois | write X X | xargs | xfd | xlsfonts | xset | xterm | xrdb Y yacc | yes | yppasswd Z zcat