The Linux command console contains various methods to help you when you are stuck trying to figure out a command or an argument. For example, if there is command you are trying to figure out and cannot seem to remember it, you can simply type “help”. This will bring up a populated list of commands and some of their arguments. If you wish to see more arguments for a command, simply type ” –help” after the command for a list of arguments and their effects on the command. For example, if we wanted to see a list of arguments for the “ls” command, we would type “ls –help”. This will display a list of all the arguments for “ls” and their effect on the command.
“man”
The “man” command can be used to obtain detailed information about a command or to view a list of all of the commands and descriptions that contain the word you specify. To get detailed information about a command; type “man [command]”, where command is a command, like “ls”.
To view a list of all of the commands and descriptions that contain a specified word; type “man –k [word]”, where [word] is a word like “finger”.
COMMUNICATION
Command
Action
dig
Query DNS Server
ftp
Transfer files across a remote network site
login
Login to a system
rsync
Transfer files, particularly across a network
scp
Securely copy files to a remote system using ssh
sftp
Interactive file transfer program which uses ssh for security
ssh
Login to a remote system securely and run commands on that system
COMPARISONS
Command
Action
cmp
Compare two files, byte by byte
comm
Compare lines in two sorted files
diff
Compare two text files, line by line
diff3
Compare three files, line by line
sdiff
Compare and interactively merge two files
FILE MANAGEMENT
Command
Action
cat
Concatenate files or display them
chattr
Change attributes on an ext2 file
chgrp
Change group of files
chmod
Change access modes on files
chown
Change ownership of files
chsh
Change login shell
cp
Copy files
csplit
Split a file into pieces with a specfic size or at specific locations
dd
Copy files in raw disk form
file
Determine’s a files type
head
Show the first few lines of a file
hexdump
Display files in hexadecimal format
less
Display files by screenful, forward and backward
ln
Create file name aliases
ls
Lists files and directories
md5sum
Compute MD5 checksum
merge
Merge changes from different files
mkdir
Create a directory
more
Display files by screenful, forward only
mv
Move or rename files and directories
newgrp
Change current group
od
Display files in octal form
pwd
Print working directory
rm
Remove files
rmdir
Remove directories
sha1sum
Compute the SHA1 checksum
shred
Securely delete files
split
Split files evenly
tac
Print lines of a file in reverse order
tail
Show the last few lines of a file
tailf
Follow the growth of a logfile
touch
Update the timestamps and create the file if it doesn’t exist
wc
Count lines, words, and characters
MEDIA
Command
Action
cdparanoia
Rip a CD while providing extra features
cdrdao
Copy a CD
eject
Eject a removable disk or tape
genisoimage
Generate a binary image froma directory tree
icedax
Rip a CD or DVD to create a computer-friendly WAV format
readom
Read or write data to a CD or DVD
volname
Provide the volume name of a CD-ROM
wodim
Record to a CD or DVD
PRINTING
Command
Action
lpq
Show status of print jobs
lpr
Send to the printer
lprm
Remove print job
lpstat
Get printer status
pr
Format and paginate for printing
PROGRAMMING
Command
Action
ar
Create and update library files
as
Generate object file
bison
Generate parsing tables
cpp
Preprocess C code
flex
Lexical analyzer
g++
GNU C++ compiler
gcc
GNU C compiler
ld
Link editor
ldd
Print shared library dependencies
m4
Macro processor
make
Create programs
ranlib
Regenerate archive symbol table
rpcgen
Translate RPC to C code
yacc
Generate parsing tables
SEARCHING
Command
Action
apropos
Search manpages for the topic
egrep
Extended version of grep
fgrep
Search files for literal words
find
Search the system for files by name and take a range of possible actions
grep
Search files for text patterns
locate
Search a preexisting
look
Search file for string at the beginning of lines
strings
Search binary files for text patterns
updatedb
Update the locate database
whereis
Find command
which
Print pathname of a command
SHELL PROGRAMMING
Command
Action
basename
Remove leading directory components from a path
echo
Repeat command-line arguments on the output
envsubst
Substitute the value of environment variables into strings
expr
Perform arithmetic and comparisons
mktemp
Generate temporary filename and create the file
printf
Format and print command-line arguments
sleep
Pause during processing
test
Test a condition
SYSTEM STATUS
Command
Action
at
Execute commands later
atq
Show jobs queued by at
atrm
Remove jobs queued by at
crontab
Have commands or scripts set to run on a scheduled basis
date
Display or set date
df
Show free disk space
du
Show disk usage
env
Show environment variables
finger
Display information about users
free
Show free and used memory
hostname
Display information about users
kill
Terminate a running command
printenv
Show environment variables
ps
Show processes
quota
Display disk usage and limits
stat
Display file of filesystem status
stty
Set or display terminal settings
top
Display tasks currently running
tty
Display filename of the terminal connected to standard input
uname
Display system information
vmstat
Show virtual memory statistics
who
Show who is logged in
TEXT PROCESSING
Command
Action
col
Process control characters
cut
Select columns for display
emacs
Work environment with powerful text-editing capabilities
ex
Line editor underlying vi
expand
Convert tabs to spaces
fmt
Produce roughly uniform line lengths
fold
Break lines
gawk
Process lines or records one by one
groff
Format troff input
gs
Display PostScript or PDF file
ispell
Interactively check spelling
join
Merge different columns into a databse
paste
Merge columns or switch order
rev
Print lines in reverse
sed
Noninteractive text editor
sort
Sort or merge files
tr
Translate (redefine) characters
unexpand
Convert spaces to tabs
uniq
Find repeated or unique lines in a file
vi
Visual text editor
vim
Enhanced version of vi
MISCELLANEOUS
Command
Action
bc
Arbitrary precision calculator
cal
Display calendar
clear
Clear the screen
info
Get command information from the GNU hypertext reader
man
Get information on a command
nice
Reduce a job’s priority
nohup
Launch a command that will continue to run after logging out
openvt
Run a program on the next available virtual terminal
passwrd
Set your login password
script
Produce a transcript of your login session
su
Become a different user, often the superuser
sudo
Execute an authorized command as root or another user
tee
Simultaneously store output in file and send to screen
