Linux Commands (Quick Reference)

Here are few commands for quick reference.
Commands in detail will be discussed later.

File/Directory Basics
ls           -List Files
cp           -Copy files
mv           -Move files
rm           -Delete files
ln           -Link files
cd           -Change directory
pwd          -Print current directory name
mkdir        -Create directory
rmdir        -Delete directory

File Viewing
cat          -View files
less         -Page through files
head         -View file beginning
tail         -View file ending
nl           -Number lines
od           -View binary data
xxd          -View binary data
gv           -View Postscript/PDF files
xdvi         -View TeX DVI files

File Creation and Editing
emacs        -Text editor
vim          -Text editor
umask        -Set default file protections
soffice      -Edit Word/Excel/PowerPoint docs
abiword      -Edit Word documents
gnumeric     -Edit Excel documents

File Properties
stat         -Display file attributes
wc           -Count bytes/words/lines
du           -Measure disk usage
file         -Identify file types
touch        -Change file timestamps
chown        -Change file owner
chgrp        -Change file group
chmod        -Change file protections
chattr       -Change advanced file attributes
lsattr       -List advanced file attributes

File Location
find         -Locate files
slocate      -Locate files via index
which        -Locate commands
whereis      -Locate standard files

File Text Manipulation
grep         -Search text for matching lines
cut          -Extract columns
paste        -Append columns
tr           -Translate characters
sort         -Sort lines
uniq         -Locate identical lines
tee          -Copy stdin to a file and to stdout simultaneously

File Compression
gzip         -Compress files (GNU Zip)
compress     -Compress files (Unix)
bzip2        -Compress files (BZip2)
zip          -Compress files (Windows Zip)

File Comparison
diff         -Compare files line by line
comm.        -Compare sorted files
cmp          -Compare files byte by byte
md5sum       -Compute checksums

Disks and Filesystems
df           -Show free disk space
mount        -Make a disk accessible
fsck         -Check a disk for errors
sync         -Flush disk caches

Backups and Remote Storage
mt           -Control a tape drive
dump         -Back up a disk
restore      -Restore a dump
tar          -Read/write tape archives
cdrecord     -Burn a CD
rsync        -Mirror a set of files

Printing
lpr          -Print files
lpq          -View print queue
lprm         -Remove print jobs

Spelling Operations
look         -Look up spelling
aspell       -Check spelling interactively
spell        -Check spelling in batch

Processes
ps           -List all processes
w            -List user’s processes
uptime       -View the system load
top          -Monitor processes
xload        -Monitor system load
free         -Display free memory
kill         -Terminate processes
nice         -Set process priorities
renice       -Change process priorities

Scheduling Jobs
sleep        -Wait for some time
watch        -Run programs at set intervals at Schedule a job
crontab      -Schedule repeated jobs

Hosts
uname        -Print system information
hostname     -Print the system’s hostname
ifconfig     -Set/display network information
host         -Look up DNS
whois        -Look up domain registrants
ping         -Check if host is reachable
traceroute   -View network path to a host

Networking
ssh          -Securely log into remote hosts
telnet       -Log into remote hosts
scp          -Securely copy files between hosts
sftp         -Securely copy files between hosts
ftp          -Copy files between hosts
evolution    -GUI email client
mutt         -Text-based email client
mail         -Minimal email client
mozilla      -Web browser
lynx         -Text-only web browser
wget         -Retrieve web pages to disk
slrn         -Read Usenet news
gaim         -Instant messaging/IRC
talk         -Linux/Unix chat
write        -Send messages to a terminal
mesg         -Prohibit talk/write

Audio and Video
grip         -Play CDs and rip MP3s
xmms         -Play audio files
cdparanoia   -Rip audio
audacity     -Edit audio
xcdroast     -Burn CDs

References:
1) http://linux.about.com
2) www.linux.org

Refer above sites for more details
i.e. commands with descriptions, usage e.t.c.