Kratek povzetek snovi za prostopni kolokvij (A short summary of the material for the entrance exam)

COMMANDS:
man - manual pages
less, more - paginate output
cd - Change Directory
pwd - show current directory
ls - list directory content
cat - output file to stdout (screen)
echo - output argument to stdout
env - output environment
ps - list proceses
grep - filter text
ifconfig - show network interfaces
ip - show network settings
route - show routes
arp - show the Address Resolution Protocol table
sleep - block for N seconds
kill - kill process
killall - kill processes with a certain name
top - display a list of processes
source - interpret the commands inside a file
export - set an environment variable
chown - change owner
chmod - change permissions
which - which program would be run
head - output the first few lines of a file
tail - output the last few lines of a file
wc - word count
bg - run the stopped program in the background
fg - get the program from the background to the foreground
mount - attach a filesystem to the current directory structure
find - search for files in a directory hierarchy
sed - stream editor for filtering and transforming text

DIRECTORIES:

cd /SOME_PATH # move to /SOME_PATH 
cd SOME_PATH # move to $PWD/SOME_PATH
./ # current directory
.some_name # a file called .some_name which is hidden
../ # 1 level "up" (parent directory)
~ # $HOME
~/ # $HOME/
~some_name # the home dir of some_name
file~ # a file called file~
f~i~l~e # a file called f~i~l~e
~- # $OLDPWD

ENVIRONMENT:

PWD # current directory
OLDPWD # PWD before the last successfull cd
PATH # a ":" separated list of directories of programs
   (DOES NOT CONTAIN THE CURRENT DIRECTORY by default)
DISPLAY 

SYMBOLS:
>
  prog1 > file1 # redirect stdout from prog1 into file1
>> # 
  prog1 >> file1 # append stdout prog1 to file1
<
  prog1 < file1 # redirect file1 to stdin of prog1
|
  prog1 | prog2 # redirect stdout of prog1 to stdin of prog2
A>&B
  prog1 2> file1 # redirect stderr of prog1 to file1
  prog1 >&2 # redirect stdout of prog1 to stderr
  prog1 2>&1 # redirect stderr of prog1 to stdout
  prog1 2>&1 | less
  
& 
  prog1 & prog2 # |---prog1---| &
                   |-----prog2------|
&&
  prog1 && prog2 # run prog2 after prog1 terminated successfully
;
  prog1; prog2 # run prog2 after prog1 (ignore the return code)
{
}
  { prog1; prog2; } # run prog1 and prog2 in a sub-shell

$
  echo $PATH # echo the_value_in_PATH
  echo $PWD$PATH # echo the curr. dir + the path
  
`
  `prog1` -> get the output of prog1 into a string
  export WHERE_I_AM=`pwd`
  export CURRENT_DATE=`date`
  
"
  "string with escape sequences"
'
  'normal(raw) strings'

. # source
  . file # same as source file
  
CTRL+C - break (program)
CTRL+Z - stop the current program, put it into the background
CTRL+D - end of file
CTRL+R - search history

IPs:
Local networks:
  192.168.0.0/16, (192.168.0.0 - 192.168.255.255) 
  172.16.0.0/12, (172.16.0.0 - 172.31.255.255)
  10.0.0.0/8, (10.0.0.0 - 10.255.255.255)
Other special networks:
  127.0.0.0/8 - localnet
  169.254.0.0/16 - link-local addresses