#ADVANCED BASH SCRIPTING#
	

#special characters
#                 	 -> 	comment
\# 		  	#-> 	#scaped comment
echo ${PATH#*:}	  	#->	#parameter substitution
echo $(( 2#101011 ))	#->	#base conversion

#;
command; command	#->	#separates commands

#;;
case "$var" in
	a) echo "\var = a" ;;	#case line terminator
esac

#;;& - ;&			case (bash v4+) terminator

#.			->	current directory
./scriptname.sh

#"			->	scapes most special characters in a string

#'			->	scapes all special characters in a string

#,			->	links arithmetic operations & returns only the last one
let "t2 = ((a = 9, 15 / 3))"

#			->	concatenates strings
for file in /{,usr/}bin/*filename
#	      ^includes "usr" to form /usr/bin

#,, ,			->	lowercase character coversion
var="STRING"
echo "${var,,}"

#\			->	escape character
echo \""quotation signs\""

#`			->	command substitution
echo x=`echo "$x + 1" | bc`

#:			->	No-OP/NOP = true = 0
:
echo $?	#prints 0
#-
: ${name=`whoami`}

: ${1?"Use: 0"}		#->	#command placeholder

: > data.log		#->	#empties file data.log

:()			#->	#used as function name

!			#->	inverts/negates the effect of 'test' operators
x=0
if [ $x != "10"]	#->	if x not equal 10

*			#->	globbing filename expansion
rm -rf /*.*

**			#->	represents exponentiation/extended file match

?			#->	conditional test/single character matching
(( var1=var2<98?9:21 ))

#if [ "$var2" -lt 98 ]
#then
#	var1=9
# else
#	var1=21
#fi

#$			->	variable expansion/end-of-line in regex

#${}			->	parameter substitution

#$'...'			->	quoted string expansion

#$*,$@			->	positional parameters

#$?			->	exit status

#$$			->	script's own PID

#()			->	command group
(a=hi; echo $a)			#starts a subshell/not visible to the rest of the script

#-
a=123
( a=321; )

echo "a = $a"		#->	echoes 123

#-
array=(a b c)

#{}			->	brace expansion
echo \"{these,appear,quoted}\"	#"these" "appear" "quoted"

#-
cat {file1,file2,file3} > combined_file.txt

#-
cp file.{txt,backup}	#->	#copies "file.txt" to "file.backup"

#-
echo {file1,file2}\ :{\ a," b",' c'}
#spaces need to be scaped

#{a..z}		->	extended brace expansion
echo {a..z}		#a b c d e.....z

#-
echo {0..9}		#0 1 2 3 4...n

#-
base64_charset=( {A..Z} {a..z} {0..9} + / = )

#-
a=123
{ a=321; }		#codeblock
echo "a = $a"		#echoes 321

#-
ls . | xargs -i -t cp ./{} $1
#text placeholder

#{} \;			->		pathname - not a shell builtin/used w/ 'find' command

#[]			->		test expression

#[[]]			->		(fexible) test expression

#[]			->		array

#$[]			->		integer expansion
a=1
b=2

echo $[$a+$b]		#evaluating integer expression

#(())			->		integer expansion

#>, &>, >&, >>, <, <>	#redirection

#(command) >, < (command)		#process substitution

#<, >			->		ASCII comparisson/dictionary word order
if [[ "$string1" < "$string2" ]]

#\<, \>			->		word boundary
grep '\<word\>' file.txt

#>|			->		force redirection

#||			->		logical OR

#&			->		background job
sleep 10 &

#&&			->		logical AND

#-			->		option prefix

#~			->		home directory

cd ~user

cd ~

cd ~/

cd ~:

#~+			->		current working directory/$PWD

#~-			->		previous working directory/$OLDPWD

#=~			->		regular expression match


							###########
							#VARIABLES#
							###########


#valid
echo "$var"

echo "${var}"

var="a b c   d"
echo $var				#a b c d
echo "$var"				#a b c   d
					#preserves whitespace

var1=20 var2=21 var3=22			#permitted but not portable

var_space=2\ ---\ word
echo "$var_space"			#2 --- word
					#spaces were scaped

var=23
unset var
echo "var = $var"			#unset variables get null value

var0=					#null value variable/uninitialized variable

let "var0 += 1"				#arithmetic operations using uninitialized variable are possible
echo "$var0"

a=11bbcc
b=${a/11/aa}				#substitute '11' w/ 'aa'

echo "b = $b"				#aabbcc

#declare
declare -i var				#declares var as integer
declare -r var				#declares var as read only
declare -r -i var			#declare var as read only and integer

{ var=112233; }				#local variable / visible in codeblocks or functions
var=123					#environmental variable / visible to the shell and user

$0..$9 ${10} ${11} ${12}		#positional parameters after $9 must be bracketted

$* & $@					#access all parameters

shift 3					#shift reassigns positional parameters
#$1 <- $2, $2 <- $3, $3 <- $4

n=3; shift $n				#shifts 3 positions


							#########
							#QUOTING#
							#########


grep '[Ww]ord' *.txt			#quoting protects meaning

echo "$(ls -l)"				#suppressing echo newline

#COMMAND $var1 $var2 $var3
#COMMAND "$var1" "$var2" "$var3"
#COMMAND "$var1 $var2 $var3"

echo -e "\v\v\v\v"			#vertical tabs

echo -e "\040"				#octal ASCII character

echo $'\n'				#echo $'\letter' construction makes '-e' unnecessary
					#newline

echo $'\a'				#beep (depends on terminal)

echo $'\t \044 \t'			#echoes ASCII character

echo $'\t \x44 \t'			#echoes hexdecimal number

var=$'\044'				#asigning ASCII character to var

ABC=$'\101\102\103\010'			#echoes "ABC"

#\"					#literal "
echo "\"Hello"\"

#\$					#literal dollar sign
echo "Cost is \$9.99"

#\\					#\
echo "\\"				#echoes "\"

echo '\'				#same effect


					#escaping & quoting
echo \z			#z
echo \\z		#\z
echo '\z'		#\z
echo '\\z'		#\\z
echo "\z"		#\z
echo "\\z"		#\z

					#command substition
echo `echo \z`		#z
echo `echo \\z`		#z
echo `echo \\\z`	#\z
echo `echo \\\\z`	#\z
echo `echo \\\\\\z`	#\z
echo `echo \\\\\\\z`	#\\z
echo `echo "\z"`	#\z
echo `echo "\\z"`	#\z

					#here-doc
cat <<EOF
\z
`EOF			#echoes \z

cat <<EOF
\\z
`EOF			#echoes \\z
#

#
cat <<var
echo `date&&who`
`var					#command substitution


echo 'hello
there'			#echoes "hello there"

echo hello\
there			#echoes "hellothere" - newline is scaped

echo "hello\
there"			#same - newline scaped

echo 'hello\
there'			#echoes "hello\ there"



							####################
							#Exit & Exit Status#
							####################


true
echo "exit status \"true\" = $?"	#0

! true					#negating true
echo "exit status \"true\" = $?"	#1

true
!true					#not negating, repeating last "true" command

ls | nonexistent_command
echo $?					#127

! ls | nonexistent_command
echo $?					#0


							#################
							#Test Constructs#
							#################



[[ $var -lt $var ]]			#return exit status

(( 0 && 1 ))				#AND
echo $?					#exit status 1
#but
let "num = (( 0 && 1 ))"
echo $num				#exit status 0
#but
let "num = (( 0 && 1 ))"
echo $?					#exit status 1


(( 200 || 11 ))				#OR
echo $?					#0
#
let "num = (( 200 || 11 ))"
echo $num				#1
#
let "num = ((200 || 11 ))"
echo $?					#0


(( 200 | 11 ))				#bitwise OR
echo $?					#0
#
let "num = (( 200 | 11 ))"
echo $num				#203
#
let "num = (( 200 | 11 ))"
echo $?					#0


if cmp a b &> /dev/null			#diffing w/ if
then echo "Identical files"
	else echo "Files differ"
	fi
#
if grep -q word filename
then echo "File contains word"
fi
#
word=linux
lettr_seq=inu

if echo "$word" | grep -q "$lettr_seq"	#'-q' suppresses output
then
	echo "$lettr_seq found in $word"
else
	echo "$lettr_seq not found in $word"
fi
#
if command_with_status_0_unless_error
then echo "command succeeded"
else echo "command failed"
fi


#elif

#if [ condition1 ]
#then
# command
#elif [ condition2 ]
# then
#command
#else
# command
#fi

#&&, ||, <, > work inside [[]] - not inside []
if [[ -e $file  ]]			#no filename expansion/word splitting
then
	echo "File exists"
fi

'---'

dir=/dir/dir

if cd "$dir" 2>/dev/null; then		#hides error msg
	echo "In $dir"
else
	echo "Can't cd to $dir"
fi

'---'

foo=20
bar=22

[ "$foo" -ne "$bar" ] && echo "$foo" NEQ "$bar"

home=/home/home
[ -d "$home" ] || echo "$home doesn't exist"

'---'

dev0="/dev/sda2"			# / (directory)
if [ -b "$dev0" ]
then
	echo "$dev0 is block device"
fi

#

dev1="/dev/ttyS1"			#PCMCIA
if [ -c "$dev1" ]
then
	echo "$dev1 is character device"
fi

#

function show_IO()
{
	[ -p /dev/fd/0 ] && echo PIPE || echo STDIN
}

show_IO "Input"
echo "Input" | show_IO

#

[[ $a == z* ]]				#true if $a starts w/ "z"
[[ $a == "z*" ]]			#true if $a = z*

[ $a == z* ]				#file globbing/word splitting
[ "$a" == "z*" ]			#true if $a = z*

#

if [[ "$a" < "$b" ]]
if [ "$a" \< "$b" ]			#'<' needs scaping between "[ ]"

#

if [[ "$a" > "$b" ]]
if [ "$a" \> "$b" ]			#'>' needs scaping too

#

if [ "$expr1" -a "$expr2" ]		#logical AND
					#true if both are true

if [ "$expr1" -o "$expr2" ]		#logical OR
					#true if either is true

#

echo $(( 1 && 2 )) $((3 && 0)) $((4 || 0)) $((0 || 0))

#

let "op = ((5+3, 7-1, 15-4))"				#last arithmetic op to right value assigned to $op
echo "op = $op"						#echoes 11

'---'

let "opn = ((a = 24/3, 15/3))"
echo "opn = $opn   a = $a"				#'$opn' echoes 5 - '$a' echoes 8 

'---'

let "a = ((b = 5+3, ((2-1)) + ((3-2)) ))"
echo "a = $a"						#'$a' echoes 2
let "c = $b+$a"
echo "c = $c"						#'$c' echoes 10

'---'
							#hexadecimal values
echo "$((0x9abc)) $((0x9abd))"				#39612 & 39613




						###################
						###INTERNAL VARS###
						###################


$BASH				#bash path
$BASH_ENV			#bash startup "#!/usr/bin/env bash"
$BASHPID			#bash process ID - not the same as "$$"
$BASH_VERSION[n]		#details about bash version
$CDPATH				#'cd' command search path
$DIRSTACK			#'dirs' command stack
$EDITOR				#default editor (vi/emacs)
$EUID				#"effective" user ID
$FUNCNAME			#name of current function

func ()
{
echo "$FUNCNAME executing"	#echoes "func"
}

$GLOBIGNORE			#filename patterns excluded from matching
$GROUPS				#groups current user belongs to
$HOME				#user home directory
$HOSTNAME			#set by gethostname() function
$HOSTTYPE			#hardware architechture - like "$MACHTYPE" but less detailed
$IFS				#internal field separator (fields, word boundaries, character strings)
$IGNOREEOF			#ignore end-of-file
$LC_COLLACE			#controls collation in filename expansion
$LC_CTYPE			#cotrols character interpretation in globbing/pattern matching
$LINENO				#line number where this variable appears
$MACHTYPE			#...
$OLDPWD				#previous working directory
$OSTYPE				#...
$PATH				#path to binaries
$PIPESTATUS			#holds exit status
$PPID				#process ID
$PROMPT_COMMAND			#
$PS1				#primary prompt
$PS2				#secondary...
$PS3				#...
$PS4				#...
$PWD				#working directory
$REPLY				#"read" command default value
$SECONDS			#...
$SHELLOPTS			#lists enabled shell options
$SHLVL				#shell nesting level
$TMOUT				#shell login time limit
$UID				#user ID



						#######################
						#positional parameters#
						#######################




$0, $1, $2, ...			#parameters supplied to the script

$#				#number of arguments/positional paramenters

$*				#all parameters (must be quoted)

$@				#same as "$*" (should be quoted)



						#########################
						####special parameters###
						#########################


$-				#tests script interactivity

$!				#last backgorund process ID

$_				#command final argument

$?				#exit status

$$				#script own PID



						#########################
						######type setting#######
						#########################



declare -r			#readonly (same as 'readonly var')

declare -i			#integer

declare -a			#array

declare -f			#function

declare -x			#export


declare | grep HOME		#echoes variable
#declare | grep SHELL
#declare | grep UID

var=1
declare | grep var


$RANDOM				#generates random integer (0 - 32767)




							##################
							######STRINGS#####
							##################


				#string lenght
string=abcABC123CBAcba

echo ${#string}
echo `expr lenght $string`
echo `expr "alph" : '.*'`

				#matching substring beginning - substring=regular expression
echo `expr match "$string" 'abc[A-Z]*.2'`
echo `expr "$string":'abc[A-Z]*.2'`

				#index
echo `expr index "$string" C12`
echo `expr index "$string" 1c`	#'c' position before 1

				#extraction
echo ${string:0}		#extract from position 0/echoes "abcABC123CBAcba"
echo ${string:1}		#from position 1/echoes "bcABC123CBAcba"
echo ${string:7}		#.../echoes "23CBAcba"

echo ${string:7:3}		#extract 3 characters including position 7/echoes "23A"

echo ${string:(-4)}		#from right to left extract 4 characters/echoes "Cabc"

echo ${*:2}			#echoes second and following parameter
echo ${@:2}			#same as above

echo ${*:2:3}			#echoes three positional paramenters starting at the second one

				#expr substr $string $position $lenght
echo `expr substr $string 1 2`	#start at char 1 extract 2
echo `expr substr $string 4 3`	#start at char 4 extract 3

				#expr match "$string" '\(regex\)'
echo `expr match "$string" '\(.[b-c]*[A-Z]..[0-9\)'`

				#expr "$string" : '\(regex\)'
echo `expr "$string" : '\(.[b-c]*[A-Z]..[0-9]\)'`
echo `expr "$string" : '\(.......\)'`

				#expr match "$string"'.*\(regex\)'
echo `expr match "$string" '.*\([A-C][A-C][A-C][a-c]*\)'`
				#expr "$string" : '.*\(regex\)'
echo `expr "$string" : '.*\(......\)'`


				#SUBSTRING REMOVAL#

				#${string#substring}
echo ${string#a*C}
				#${string##substring}
echo ${string##a*C}

				#substring parameterization
X='a*C'

echo ${string#$X}
echo ${string##$X}

				#${string%substring}

EXT=TXT
ext=txt

for i in ${ls *.$EXT}
do
	mv -f $i ${i%.$EXT}.$ext
	#replaces 'TXT' with 'txt'
done

				#${string%substring}
echo ${string%b*c}		#abcABC123CBAc

				#${string%%substring}
echo ${string%%b*c}		#c

				#substring replacement
				#${string/substring/replacement}
echo ${string/abc/xyz}		#replaces first "abc" w/ "xyz"

				#${string//abc/xyz}
echo ${string//abc/xyz}		#replaces all "abc" w/ "xyz"


				#parameterization
char=abc
repl=000

echo ${string/$char/$repl}	#000ABC123CBAcba

echo ${string//$char/$repl}	#000ABC123CBA000


				#${string/#substring/replacement}
echo ${string/#abc/XYZ}		#replaces first match w/ "XYZ"

				#${string/%substring/replacement}
echo ${string/%abc/XYZ}		#replaces last match w/ "XYZ"


						########################
						#parameter substitution#
						########################


				#${parameter}
				#":" makes result different only when params are declared but null
id=${USER}-on-${HOSTNAME}	#concatenating variables
echo "$id"

PATH=${PATH}:/opt/bin		#temporarily adds "/opt/bin" to $PATH

				#${parameter-default}, ${parameter:-default}
var1=1
var2=2

echo ${var1-$var2}
echo ${var3-$var2}		#unset var3 now set to value of var2

echo ${user-`whoami`}		#unset var "user" echoes result of "whoami" command

				#${param=default}, ${param:=default}
echo ${var=abc}			#
echo ${var=xyz}			#if var unset set it to default/var already set so no change

				#${param+alt_val}, ${param:+alt_val}
a=${param1+xyz}
echo "a = $a"			#a =

param2=
a=${param2+xyz}
echo "a = $a"			#a = xyz

param3=123
a=${param2+xyz}
echo "a = $a"			#a = xyz

				#${param?err_msg}, ${param:?err_msg}
: ${ZZX?"ZZX not set"}		#ZZX not set, script exits with error msg

				
						############################
						#var length/subtrng removal#
						############################

${#var}				#length of $var

${var#pattern}
${var##patter}			#remove shortest (#) or longest (##) front-end match of $pattern in $var

${var%pattern}
${var%%pattern}			#remove shortest (%) or longest (%%) back-end match of $pattern in $var

${var:pos}			#$var expanded from "position"
${var:pos:len}			#$var expansion to max "length" from "position"
${var/pattern/replacement}	#match of "pattern" in $var replaced by "replacemente"
				#if "replacement" omitted "pattern" gets deleted
${var//patt/replc}		#all matches of "patt" get replaced bu "replc"
				#same as above

${var/#patt/replc}		#if $var prefix matches "patt" substitute "replc" for "patt"
${var/%patt/replc}		#if $var suffix matches "patt" subts "replc" for "patt"

${!varprefix*}
${!varprefix@}			#matches all previously declared variables with "varprefix"



							#################
							######LOOPS######
							#################



#for arg in [list]
#do
# command(s)
#done
#

for arg in [list]; do		#if do is in same line ";" is needed

for planet in Mercury Venus Earth .....p
do
	echo $planet
done

#
filelist="/path/tofile/file1
/path/tofile/file2
/path/tofile/file3
/path/tofile/file4"

for file in $filelist
do
	if [ ! -e "$filelist" ]; then
		echo "$filelist none existent"; echo
		continue
	fi
done

#
for file in *			#filename globbing
do
	ls -l "$file"
done

#
for file in [jx]*		#list files beginning with "j" or "x"
do
	rm -f $file		#remove them
done

#
passwd=/etc/passwd
				#filtering file content (field 1)
for user in $(awk 'BEGIN{FS=":"}{print $1}' < "$passwd")

#
echo_blah ()
{
	echo "blah blah blah"
}

for word in $(echo_blah)	#takes function (echo_blah) output
do
	echo $word
done

#
LIMIT=10

for ((a=1; a <= LIMIT; a++))	#C-like syntax

#
				#the comma permits concatenating operations
for ((a=1, b=1; a<=LIMIT; a++, b++))
do		#         ^    ^ incrementing two variables at the same time
	echo -n "$a-$b"
done

#
for ((n=1; n<=10; n++))
	{
		echo -n "* $n *"
	}			#replacing "do-done" with "{}"
#


				#while
var=0
LMT=10

while [ "$var" -lt "$LMT" ]
do
	echo -n "$var"
done
#

while [ "$var" -lt "$LMT" ]; do	#if "do" on the same line ";" is needed
	echo -n "$var"
done
#

var=unset
previous=$var			#multiple conditions while

while echo "previous-var = $previous"
	echo
	previous=var
	[ "$var" != end ]
do
	echo "Input variable #1 (end) "
	read var
	echo "variable #1 = $var"
done

exit 0

#
t=0

condition()
{
	((t++))

	if [ $t -lt 5 ]
	then
		return 0
	else
		return 1
	fi
}

while condition			#while + function
do
	echo "Still going: t = $t"
done
#

cat $file |
while read line
do
	...
done
#
#
while read value
do
	rt=$(echo "scale=$SC; $rt + $value" | bc)
	((ct++))
done

am=$(echo "scale=$SC; $rt / $ct" | bc)

echo $am; return $ct

} <"$datafile"
#

#until
#do
# command
#done

#until [condition-is-true];do
LMT=10
var=0

until ((var > LMT))
do
	echo -n "$var"
	((var++))
done

exit 0
#
#
				#nested loops
outer=1

for a in 1 2 3 4 5
do
	"$outer in outer loop"
done

inner=1

for b in 1 2 3 4 5
do
	echo "$inner in inner loop"
	let "inner+=1"
done

let "outer+=1"
echo
done

exit 0
#
#
				#break
LMT=19

echo "Print 1 through 20, except 3 & 11"

a=0

while [ $a -le "LMT" ]
do
	a=$(($a+1))

	if [ "$a" -eq 3 ] || [ "$a" -eq 11 ]
	then
		continue
	fi

	echo -n "$a "
done

echo; echo
echo Printing 1 through 20, something happens after 2.
#
#

a=0

while [ "$a" -le "LMT" ]
do
	a=$(($a+1))

	if [ "$a" -gt 2 ]
	then
		break
	fi

	echo -n "$a "
done

echo; echo; echo

exit 0
#
#

for outerloop in 1 2 3 4 5
do
	echo -n "Group $outerloop: "

	for innerloop in 1 2 3 4 5
	do
		echo -n "$innerloop "

		if [ "$innerloop" -eq 3 ]
		then
			break
		fi
	done
	echo
done

echo

exit 0
#
#

for outer in I II III IV V		#outer loop
do
	echo; echo -n "Group $outer: "

	#----------------------------

	for inner in 1 2 3 4 5 6 7 8 9 10
	do
		if [[ "$inner" -eq 7 && "$outer" = "III" ]]
		then
			continue 2	#continue loop on 2nd level "outer loop"
					#replace above line with a simple "continue"
					#to see normal loop behavior
			fi

			echo -n "$inner "	# 7 8 9 10 will not echo on "Group III"
		done
		#--------------------------

	done

	echo; echo

	exit 0
#
#

while true
do
	for n in .iso.*
	do
		[ "$n" = ".iso.opts" ] && continue
		beta=${in#.iso.}
		[ -r .Iso.$beta ] && continue
		[ -r .lock.$beta ] && sleep 10 && continue
		lockfile -r0 .lock.$beta || continue
		echo -n "$beta: " `date`
		run-isotherm $beta
		date
		ls -alF .Iso.$beta
		[ -r .Iso.$beta ] && rm -f .lock.$beta
		continue 2
	done
	break
done

exit 0
#
#

#testing & branching
#case(in)/esac
#case "$var" in
#"$condition1"
#command
#;;
#"$condition2"
#command
#;;

echo; echo "Hit a key..."
read key

case "$key" in
	[[:lower:]]	) echo "Lowercase!";;
	[[:upper:]]	) echo "Upper!";;
	[0-9]		) echo "Digit!";;
	*		) echo "Other";;
esac

exit 0
#
#

			#menus using case

clear

echo "Contacts"
echo "Choose person: "
echo
echo "[E] - Evans"
echo "[J] - Jones"
echo "[S] - Smith"
echo

read person

case "$person" in
	"E" | "e")
		echo
		echo "Roland Evans"
		echo "4444 Street"
		echo "(111) 222-3333"
		;;

		"J" | "j" )
			echo
			echo "Mildred Jones"
			echo "3344 Street"
			echo "(111) 222-3333"
			;;

		* )
			echo
			echo "Not registered"
			;;

		esac
		echo

		exit 0
#
#
				#testing command-line parameters
case "$1" in
	"") echo "Use: ${0##*/} <filename>"; exit $E_PARAM;;
	#${0##*/} is ${var##patter} param substitution

	-*) FIMENAME=./$1;;

	* ) FILENAME=$1;;
esac
#
#
				#menus using select
PS3='Choose vegetable: '

echo

choice_of()
{
	select vegetable
	do
		echo
		echo "favorite vegetable $vegetable"
		echo
		break
	done
}

choice_of beans rice carrots radish spinach
#	    $1   $2     $3     $4      $5

exit 0
#
#
				######################
				#command substitution#
				######################

#commands inside backticks
scr_name=`basename $0`
#to avoid errors is better to use
#xargs rm -- < filename

#using command output for another command
rm `cat filename`

#storing a list of files w/ specific extension
txt_files=`ls *.txt`
echo $txt_files
#
#same result
text_files=$(ls *.txt)
echo $text_files

#echoing unquoted removes
#trailing newline characters
#preserving trailing newline
dir_lst=`ls -l`
#
#scrambled output
echo $dir_lst
#organized output
echo "$dir_lst"

#setting content of files as vars
var1=`<filename`
var2=`cat filename`

#assigning a variable is not needed
echo "` <$0`"

#assigning a loop output to a variable
var1=`for i in 1 2 3 4 5
do
	echo -n "$i"
done`
#
#var1 = 12345
echo "var1 = $var1"
#
i=0
var2=`while [ "$i" -lt 10 ]
do
	echo -n "$i"
	let "i += 1"
done`
#
#var2 = 0123456789
echo "var2 = 0123456789"

#$() is prefered to backticks "``
file1=$(cat $filename)
file2=$(<$filename)
#it also treats backslashes different
echo `echo \\`
#no output
#
echo $(echo \\)
#outputs \
#
#it also allows nesting
words=$( wc -w $(echo * | awk '{print $8}') )


				##############################
				#####ARITHMETIC EXPANSION#####
				##############################

#variations
#using backticks
z=`expr $z + 3`
#expr performs the expansion
#
#double parentheses and let
#constructions replaced backticks
z=$(($z+3))
z=$((z+3))
#
#no assignment needed
n=0
echo "n = $n"
#n = 0
#
#(($n +=1)) is incorrect
(( n += 1 ))
echo "n = $n"
#n = 1
#
#quotes allow the use of spaces
let "z += 3"
#same as
let z=z+3
#
#
				

				##################################
				##INTERNAL COMMANDS AND BUILTINS##
				##################################

#ECHO
#prints to stdout an
#expression or variable
echo Hello
echo $a
#-n supresses terminal newline
#echo requires -e to print
#escaped characters

#using echo and command substitution
#to set a variable
a=`echo "hello" | tr A-Z a-z`
#			^converts all uppercase into lowercase
#
#
				
#PRINTF
#printf allows to print formatted strings
#
declare -r pi=3.14159265358979
declare -r dconst=31373

printf "Pi 2 decimal places = %1.2f" $pi
#
#printing a linefeed
printf "\n"
#
#inserting tab
printf "Constant = \t%d\n" $dconst
#
#formatting error messages
ERROR_DIR=609

var=nonexistent_dir

error()
{
	printf "$@" >&2
	echo
	exit $ERROR_DIR
}

cd $var || error $"%s doesn't exist!" "$var"
#
#
				
#READ'
#
#setting a variable value
echo -n "Input var1 value: "
read var1
''#no $ in front of var1 needed
  #
#setting multiple variables
echo -n "Input var1 and var2 values: "
read var1 var2
''#variables need to be separated
  #by space or tab
#
#if read is not supplied any variables
echo -n "Enter value: "
read	 #no variable supplied

var="$REPLY"
echo "\"var\" = "$var""
#
#discarding values
#in a code block
{
	read #avoids reading line #1 of the file
	read line2 #reads line #2 of the file
} <$0	#script redirects to itself

echo "Line 2 of the file is: "
echo "$line2"
echo
#
#multi-line input
echo "Enter a string ending in \\ then press <ENTER>."
echo "Enter a second string w/o \\ then press <ENTER>."

read var1
echo "var1 = $var1"
#var1 = first line second line
#the \ supresses the newline
#
echo "Enter another string terminated by \\"
read -r var2
#the -r causes the \ to be read literally

echo "var2 = $var2"
#first line \
#
#reading keystrokes w/o hitting enter
read -s -n1 -p "Press key " keys
#these option need to be in the same
#order presented in this writing
echo; echo "Key pressed was "\"$keys\""."
#
#detecting arrow keys
arrowup='\[A'
arrowdown='\[B'
arrowrt='\[C'
arrowleft='\[D'
insert='\[2'
delete='\[3'

succ=0
other=65

echo -n "Press a key... "
read -n3 key

echo -n "$key" | grep "arrowup"		#check character detection
if [ "$?" -eq $succ ]
then
	echo "Up-arrow pressed"
	exit $succ
fi
#...
#code is too long :(
#...
echo "Other key pressed"
exit $other
#
#reading a variable from a file
read variable <filename
echo "variable = $variable"
#variable is set to the first line of 'filename'
#
#reading the whole file
while read line
do
echo "$line"
done <filename
#
#


#pushd/popd/dirs
#
#pushd pushes a directory into
#the top of the directory stack
pushd directoryname
#and changes the working directory
#to directoryname
#
#popd removes the directory at the
#top of the directory stack
popd directoryname
#
dir1=/tmp/directory
dir2=/usr/directory
#changes $PWD to dir1
pushd $dir1
#changes to $dir2 
pushd $dir2
#
#pops the current directory on top (dir2)
popd
#dirs will list the directories
#in the stack
dirs
#
#


#let
#makes arithmetic operations on variables
#
let a=11			#same as 'a=11'
let a=a+5			#same as let "a = a + 5"
echo "11 + 5 = $a"
#
#let "a = a << 3"
let "a <<= 3"
echo "\"\$a\" (=16) left-shifted 3 places = $a"
#128
#
#let "a = a / 4"
let "a /= 4"
echo "128 / 4 = $a"
#32
#
#let "a = a - 5"
let "a -= 5"
echo "32 - 5 = $a"
#27
#
#let "a = a * 10"
let "a *= 10"
echo "27 * 10 = $a"
#270
#
#let "a = a % 8"
let "a %= 8"
echo "270 modulo 8 = $a (270 / 8 = 33, remainder $a)"
#
#C style operators
#increment
let a++
echo "6++ = $a"
#7
#
#decrement
let a--
echo "7-- = $a"
#6
#
#trinary operator
#
#true
let "t = a<7?7:11"
echo $t
#7
#
#true
let a++
let "t = a<7?7:11"
echo $t
#11
#
#


#eval
#evaluates strings and
#converts them into a command
a="echo"
b="Hello "
c="world!"

eval $a $b $c
#Hello world!
#
#linefeeds
y=`eval ls -l`
#linefeeds removed
echo $y
#linefeeds preserved
echo "$y"
#
#printing a sequence of variables
eval "`seq 3 | sed -e 's/.*/var&=ABCDE/'`"
#var1=ABCDE, var2=ABCDE, var3=ABCDE
#
#selecting from multiple variables
arr0=( A B C D E )
arr1=( F G H I J )
arr2=( K L M N O )

choose_arr ()
{
 eval arr_memb=\${arr${arr_numb} [elem_numb] }
 echo "Element $elem_numb of $arr_numb is $arr_memb"
}
#
#echo parameter number
params=$#
param=1

while [ "$param" -le "$params" ]
do
  echo -n "Paramter No. "
  echo -n \$$param
  echo -n " = "
  eval echo \$$param

(( param ++ ))
done

exit $?
#
#evaluating an expression
eval ${1}+=\"${x} ${y} \"
#
#
				

#set
#changes variable values
#
#setting a positional parameter
set `uname -a`
#
#reverse positional parameters
set a\ b c d\ e;

OIFS=$IFS; IFS=:;

echo

until [ $# -eq 0 ]
do
	echo "### k0 = "$k""
	k=$1:$k;
	echo "### k = "$k""
	echo
	shift;
done

set $k
echo -
echo $#
echo -
echo

for i
do
	echo $i
done

IFS=$OIFS

exit 0
#
#reassingning positional parameters
vars="one two three four five"

set -- $vars

f_parm=$1
s_parm=$2
shift; shift
r_parms="$*"

echo
echo "first param = $f_parm"
echo "second param = $s_parm" 
exit 0
#
#


#unset
#deletes shell variables
#
#unsetting a variable
var=hello

echo "variable = $var"
unset var

echo "var after unset = $var"
#var is null
#
#
				
#export
#makes variables accessible to all
#child processes of the script
#
#exporting a variable to environment
column_nmb=$2
export column_nmb
#
#
				
#getopts
#getopts uses $OPTIND and $OPTARG to attach
#options in getopts constructs
#
#the : indicates the option 'c' will be
#passed an argument (d e)
while getopts ":abc:de" Option
do
	case $Option in
		a ) #do something w/ 'a'.
			b ) #do something w/ 'b'.
			c ) #do something w/ 'c' and $OPTARG.
	esac
done
shift $(($OPTIND - 1))
#decrements the argument pointer
#so it points to the next one
#
#

#source or . (dot command)
#invokes/loads a script within a script
#
#loads data-file if it is executable
. data-file
#same effect as "source data-file"
#data-file must be present in the
#current working directory
#
#referencing data from within data-file
echo "var1 = $var1"
echo "var3 = $var3"
#
let "sum = $var2 + $var4"
echo "sum = $sum"
#
echo "message1 in data-file is \"$messg1\""
echo "message2 in data-file is \"$messg2\""
#calling a function inside data-file
messg_print
#
#passing arguments to the sourced file
source $file $arg1 $arg2
#
#

#shopt
#allows to change shell options on the fly
#
#correct directory spelling mistakes
shopt -s cdspell
#cd into unexistent directory
cd /hpme
pwd		#/home
#the shell corrected the directory's name
#
#

#caller
#
#returns the line number, function and
#script name where it is located
#
one_function ()
{
	caller 0
}
#must be inside a function
#

#true
#
#returns a successful exit status (0)
true
echo $?
#0
#
#endless loop
while true
do
	command
	command
	command
done
#

#false
#returns an unsuccessful exit status (1)
#
false
echo $?
#1

#type
#
#identifies builtin/external commands
#type 'command'
type '['
#type [
#both are the same
#
#the -a option locates commands
type -a '['
#[ is a builtin
#[ is /usr/bin/[
#

#jobs
#lists jobs running in background mode
#
jobs
#jobs identifiers:
#%N = job number (N)
#%S = job begins with string S
#%?S = contains string S
#%% = current job (last started in background or 
#stopped in background)
#%+ = current job (last started in background or
#stopped in background)
#%- = last job
#$! = last background process

#
#removing jobs from the list
disown
#

#wait
#
#suspend execution until all jobs
#running are terminated
updatedb /usr &
wait
#the rest of the script won't run until
#"updatedb /usr &" exits
#

#times
#displays execution time stats
#
times
#0m0.020s

#command
#
#disables command directive aliases and functions
command ls

#builtin
#
#runs commands as builtin temporarily disabling
#functions and external system commands w/ the same name
builtin command
#

#enable
#
#enables or disables builtin commands
#to make the shell run external commands
enable -n kill
#the shell will have to use /bin/kill
#

#autoload
#
#loads functions from external files (at first run)
#prevents function names conflicts
autoload -Uz functionname
#marks the function for autoloading, supress alias expansion
#and use zsh to load it
#

#cat/tac
#
#opens a file to stdout and concatenates
#files when combined w/ redirection (>, >>)
cat filename
#
cat file1 file2 > file3
#concatenates file1 & file2 into file3
#-n enumerates the lines
#-b enumerates the blank lines
#tac does the inverse to cat
#prints the file from end to start
cat file3
#line 3
#line 2
#line 1
#

#rev
#
#prints the lines of letter in a file
#in reverse order
rev file3
#1 enil
#2 enil
#3 enil
#

#cp
#
#copies files, overwrites files if they
#already exists
cp file1 file2
#overwrites file2 if it exists
cp -u orig_dir/* bck_dir
#copies the whole directory preventing
#identically named newer files to be overwritten
cp -a orig_dir/ bck_dir/
#copies all files in a directory tree
#

#mv
#
#moves files
mv orig_file target_dir/
#overwrites the file if it exists in
#the target directory
mv -f orig_file target_dir/
#moving a directory
mv orig_dir/ dest_dir/
#ask confirmation before overwriting files
mv -i file1 dest_dir/
#do not overwrite files
mv -n file1 dest_dir/
#

#rm
#
#remove files
rm file1
#removing a dashed-file (-filename)
rm -file2
#outputs rm: invalid option
#to delete a dashed-file
rm -- -file2
#or
rm ./-file2
#

#mkdir
#
#makes a directory
mkdir -p code/c/libs/asm #creates needed parents directories
#

#chmod
#
#changes attributes of files/directories
chmod +x file1 	#makes file1 executable
		#
chmod u+s file1 #sets "suid" permissions
		#so a user can execute file1 with the same
		#privs of the file owner
		#
chmod 644 file1 #makes file1 readable/writable to owner
		#but readable to others
chmod 444 file1 #makes file1 read-only for all except root
		#
chmod 1777 orig_dir/ #everyone has read, write and execute
		#permissions in the directory but only
		#the owner and root can delete files
chmod 111 orig_dir/  #everyone has execute-only permissions
		#but nobody except root can list the files
		#or find then using the find command
		#
chmod 000 orig_dir/  #no permissions for that directory
		#nobody can't read, write, execute or list
		#the files but you can rename the directory
		#or delete it if it is empty, can also link
		#the files but can't read, write or execute them
#

#chattr
#
#changes file attributes
chattr -i file1 #sets file1 as inmmutable
		#cannot be modified, linked or deleted
		#only root can set it to be removed
		#
chattr -s file2 #sets file1 as secure
		#when the file is deleted its block
		#is overwritten with binary zeroes
		#
chattr -u file1 #sets the file as undelete
		#when the file is deleted its contents
		#can still be retrieved (undeleted)
		#
chattr -c file2 #sets file2 to be automatically compressed
		#it will be compressed on disk writes and
		#uncompressed on disk reads
		#

#ln
#
#creates reference (alternate name) to a file
ln -s oldfile newfile 	#creates a soft link called 'newfile'
			#to the original file 'oldfile'
			#


					######################
					###COMPLEX COMMANDS###
					######################

#find
#
#execute commands on all the files
#matched by the searched options
find ~/ -name '*.txt' 	#find all files with .TXT extension
			#
find ~/ -name 'core*' -exec rm {} \;
			#find files with 'core' in their
			#name and if found execute "rm" on them
			#-exec (not the same as exec builtin)
			#
find /home/user/ori_dir -mtime -1
			#find files in the directory tree that
			#were modified last 24 hours
			#
find /home/user/ori_dir -mtime 1
			#same but EXACTLY a day ago
			#mtime = modification time
			#ctime = change time
			#atime = access time
			#
DIR=/home/user/ori_dir
find "$DIR" -type f -atime +5 -exec rm {} \;
			#find and delete all files with
			#accesstime older than five days (+5)
			#{} = placeholder for the path name
			#"-type filetype"
			#f = regular file
			#d = directory
			#l = symbolic link
			#
find /etc -exec grep '[0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*' {} \;
			#find all IP's in /etc
			#
find /etc -type f -exec cat '{}' \; | tr -c '.[:digit:]' '\n' \
	| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$'
			#filter
			#[:digit:] = digit character class (0 to 9)i
			#
find . -name "* *" -exec rm -f {} \;
			#find all files containing whitespace
			#in their name and removes them
			#
find . -name '*[+{;"\\=?~()<>&*|$ ]*' -maxdepth 0 \
	-exec rm -f '{}' \;
			#find all file inside $PWD with special characters
			#in their names
			#-maxdepth 0 = don't go inside subdirectories in $PWD
			#
inum=`ls -i | grep "$1" | awk '{print $1}'`
find . -inum $inum -exec rm {} \;
			#remove files based on their inode number
			#
#xargs
#
#applies the given commands to another
#command's output, defaults to 'echo'
#
find ~/mail -type f | xargs grep "Linux"
			#filters files including Linux inside them
			#
ls | xargs -p -l gzip
			#gzip every file in the current directory
			#one at a time
			#
find /usr/bin | xargs file
			#executes the file command on every file
			#shown in the output of the previous command
			#
ls | xargs -n 8 echo
			#-n 8 limits the output to eight columns
			#
find / -type f -print0 | xargs -0 grep -liwZ GUI | xargs -0 rm -f
			#-0 allows handling arguments containing whitespaces
			#or quotes
			#
grep -rliwZ GUI / | xargs -0 rm -f
			#same as above
			#
ls *gif | xargs -t -nl -P2 gif2png
			#converts all .GIF to .PNG
			#-P allows multiprocess execution (-P2 two processes)
			#-t prints to stderr
			#-n1 one argument per command line
			#
LNS=5
( date; uname -a ) >>logfile
echo ---------------------- >>logfile
tail -n $LNS /var/log/messages | xargs | fmt -s >>logfile
			#generate logs w/ tail end of /var/log/message
			#/var/log/messages must be readable
			#
tail -n $LNS /var/log/messages /var/log/messages | tr -d "\"'" | xargs | fmt -s >>logfile
			#removes unmatched single/double quotes
			#
NO_ARGS=1

if [ -z "$1" ]
then
	echo "Use: `baename $0` dirtocopy"
	exit $NO_ARGS
fi

ls . | xargs -i -t cp ./{} $1
			#-t sets "verbose"
			#-i sets "replace strings"
			#{} placeholder for text
			#
BADARGS=1

if [ -z "$1" ]
then
	echo "Use: `basename $0` proctokill"
	exit $BADARGS
fi

PROC_NAM="$1"
ps ax | grep "$PROC_NAM" | AWK '{print $1}' | xargs -i kill {} 2&>/dev/null
			#-i sets "replace strings"
			#{} are replacement placeholder
			#
ARGS=1
BADARG=2
NOFILE=3
if [ $# -ne "$ARGS" ]
then
	echo "`basename $0` filename"
	exit $BADARG
fi

if [ ! -f "$1" ]
then
	echo "File \"$1\" doesn't exist."
	exit $NOFILE
fi

cat "$1" | xargs -n1 | \ 
			#list file one word per line
			#
tr A-Z a-Z | \
			#change chars to lowercase
			#
sed -e 's/\.//g' -e 's/\,//g' -e 's/ /\
	/g' | \
			#filter out periods, commas
			#change spaces to linefeed
			#
sort | uniq -c | sort nr
			#remove duplicates, prefix occurrence count
			#and sort numerically
			#



#expr
#
#arithmetic operations evaluator
#
expr 3 + 5		#spaces are needed
			#returns 8
			#
expr 5 \* 3		#multiplication character
			#must be scaped
			#
var=`expr $var + 1`	#incrementing a variable
			#
var=`expr substr $string $position $length`
			#extract substring of $length
			#starting at $position
			#
a=3
b=`expr $a \> 10`	#comparing $a to 10
			#returns 0 (false)
			#"greater than" character
			#must be escaped
			#
a=3
b=`expr $a \< 10`	#comparing $a to 10
			#returns 1 (true)
			#"less than" chacrter
			#must be escaped
			#
a=3
b=`expr $a \>= 10`	#comparing $a to 10
			#"greater than or equal to" must be escaped
			#
a=3
b=`expr $a \<= 10`	#comparing $a to 10
			#"greater than or equal to" must be escaped
			#
a=12345word54321
b=`expr length $a`		#saving length of $a in $b
echo "Length of $a is $b"	#returns 14
				#
b=`expr index $a 23`		#position of character in substring
echo "position of \"2\" in $a is \"$b\""
				#that matches string (23)
				#
b=`expr substr $a 2 6`		#extract substring in position 2
echo "substring in position 2 and 6 chars long is \"$b\""
				#and with length 6
				#
#REGULAR EXPRESSIONS
#
b=`expr match "$a" '[0-9]*'`	#counting number of digits
				#
b=`expr match "$a" '\([0-9]*\)'`#matching digits at the beginning
				#of $a

#using ":" to substitute match
#
a=123zip321
echo "string is \"`expr "$a" : '\(.*\)'`\"."
				#escaped parentheses
				#match a substring
				#
echo "length of \"$a\" is `expr "$a" : '.*'`."
				#length of string
				#number of digits at the beginning
				#
echo "digits at the beginning of \"$a\" is `expr "$a" : '[0-9]*'`."
				#number of digits at the
				#beginning
				#
echo "Digits at the beginning of \"$a\" are `expr "$a" : '\([0-9]*\)'`."
				#counting digits of a string
				#
echo "First 7 characters of \"$a\" are `expr "$a" : '\(.......\)'`."
				#printing first seven chars of $a
				#
echo "Last 7 characters of \"$a\" are `expr "$a" : '.*\(.......\)'`."
				#printing last seven chars of $a
				#
strp_space=`expr "$strp_space" : '[[:space:]]*\(.*\)[[:space:]]*$'`
				#stripping white space from beginning to end.
				#


						###################
						###date and time###
						###################


echo "Number of days of current year: `date +%j`."
				#printing number of days since the year's beginning
				#
echo "Number of seconds since 1970: `date +%s`."
				#printing number of seconds since 1970 (UNIX Epoch)
				#

begn=temp			#sets beginning of filename
extn=$(date +%s)		#sets filename extension
filenm=$begn.$extn		#combines $begn.$extn
				#
echo "Temp filename = $filenm"	#prints temporary filename
				#
minhr=60
dayhr=24

diff () {
	printf '%s' $(( $(date -u -d"$target" +%s) -
			$(date -u -d"$curent" +%s)))
		}

current=$(date -u -d '2003-02-01' '%F %T.%N %Z')
target=$(date -u -d '2003-02-01' '%F %T.%N %Z')
#-

date +%N | sed -e 's/000$//' -e 's/^0//'
				#generating a random integer
				#stripping leading/trailing zeroes
				#


#at
#executes a set of commands
#at a given time
#
at 2:30 am Friday < commands-set.list
				#executes the commands set
				#friday at 2:30 AM
				#

#sleep
#pauses execution for a
#given amount of seconds ()
#
sleep 3				#pauses for 3 seconds
				#

sleep 3 h			#pauses for 3 hours
				#



#uniq
#
#removes duplicate lines
#

cat lst-1 lst-2 | sort | uniq > final.lst
				#removes duplicate lines
				#and writes output to final.lst
				#

uniq -c final.lst		#prefix number of ocurrences
				#of each word
				#

sort final.lst | uniq -c | sort -nr
				#sorts the output in reverse numerical
				#order (sort -nr)
				#

sed -e 's/\.//g' -e 's/\,//g' -e 's./ /\/g' "$1" | tr 'A-Z' 'a-z' | sort | uniq -c | sort -nr
				#filters out periods, commas and
				#linefeed then change characters
				#to lowercase and prefix occurrence
				#count and sorts numerically
				#


#cut
#extracts fields from files
#
cut -d ' ' -f1,2 /etc/mtab	#extracts the first and second
				#fields, delimited by space
				#-d is delimeter
				#

cut -d: -f1 /etc/passwd		#extracts all users from the
				#passwd file
				#


#paste
#merges different files together
#into a single, multi-column file
#
paste list-1.lst list-2.lst prices.lst
				#merges list-1 with list-2
				#into the single file prices.lst
				#


#join
#joins the contents of two files
#together but only content with
#the same tag
#
join list-1.lst list-2.lst
				#joins the contents of list-1
				#with list-2
				#
				#list-1:
				#100 shoes
				#200 laces
				#
				#list-2:
				#100 $40.00
				#200 $15.00
				#
				#result:
				#100 shoes $40.00
				#200 laces $15.00
				#



						#################
						#######GREP######
						#################


#grep is a multi-purpose file search tool
#grep can use regular expressions to match
#patterns inside the files
#
grep '[rst]ystem.$' osinfo.txt
				#searches occurrences of the word
				#"system" inside osinfo.txt
				#

				
ps ax | grep clock		#filters the output of 'ps ax'
				#to output instances of the word "clock"
				#

grep -n Linux osinfo.txt	#lists the line numbers where
				#the words are matched
				#

grep word1 *.txt | grep -v word2
				#matches all lines in text files
				#that contain word1 but not word2
				#

grep -c text *.sgml		#numbers of occurrences of "text"
				#in all .sgml files
				#
				#egrep = extended grep [grep -E]
				#fgrep = fast grep [grep -F]
				#agrep = approximate grep
				#

#wc
#prints word count to output
#
wc -w /path/to/file/filename.ext
				#outputs word count
				#
wc -l /path/to/file/filename.ext
				#outputs line count
				#
wc -c /path/to/file/filename.ext
				#outputs byte count
				#
wc -m /path/to/file/filename.ext
				#outputs character count
				#
wc -L /path/to/fiel/filename.ext
				#outputs lenght of the longest line
				#
ls *.txt | wc -l
				#wc -l will print the number
				#of lines of the first command
				#
wc [a-c]* | grep total | awk '{print $3}'
				#prints the total of the files
				#whose names begin with the
				#letter range a - b
				#


#tr
#character translation

tr A-Z '[**]' <filename.ext	#converts all uppercase letters
				#into asterisks
				#

echo "abcdef" | tr -d b-d	#echoes aef
				#
				#the -d option removes a range
				#of characters
				#
tr -d 0-9 <filename.ext		
				#deletes all digits
				#from the filename
				#
echo "abccccc" | tr -s 'c'	
				#echoes abc
				#
				#--squeeze-repeats/-s deletes repeated
				#instances of a character in a string
				#
echo "abcde12345" | tr -c b-d +
				#replaces every character with "+"
				#except the elements inside the "b-d"
				#range of characters
				#

echo "abcde12345" | tr '[:alpha:]' -
				#using POSIX classes replaces all
				#letters inside the string with "-"
				#


#iconv
#converts files from one encoding
#to another

myString="this string"
echo -n "$myString" | iconv -f UTF8 -t UTF16
				#converts the contents of
				#$myString from UTF8 to UTF16
				#


						######################
						##archiving commands##
						######################
				
#RPM
#RedHat Package Manager						
#
rpm -qf /bin/
				#shows the origins of a file
				#
rpm -qa
				#shows a list of installed RPM
				#packages in a given system
				#

rpm -i packagename.rpm
				#installs a RPM package
				#


#pax
#portable archive exchange
#makes periodic file back-ups
#
pax -wf daily_bkup.pax ~/server/files
				#makes a back-up file called
				#"daily_bkup.pax" of "~/server/files"
				#
pax -f daily_bkup.pax		
				#lists the files in the archive
				#
pax -rf daily_bkup.pax		
				#restores from linux machine to a BSD one
				#

#diff
#file comparisson utility
#returns 0 if files are identical
#and 1 if the files are different
#

diff file1.ext file2.ext
				#compares file1 with file2
				#

diff -r ~/dir1 ~/dir1
				#compares two directories
				#recursively for the filenames
				#
				#zdiff
				#compares zipped files
				#

#cmp
#compares two files and
#and shows where they differ
#

cmp file1.ext file2.ext		#comparing two files
				#cmp will retunr 0 if they are
				#identical and 1 if they differ
				#

#split/csplit
#utilities for splitting files
#into smaller chunks
#
csplit file1.ext 4		
				#splits file1 into four chunks 
				#


							#########################
							#ENCODING AND ENCRYPTION#
							#########################
							
#cksum
#
cksum /path/to/file/filename.ext
				#prints a sum based on the contents
				#of the file
				#

echo -n "word" | cksum
				#prints a sum of the word piped
				#by the echo command
				#

#uuencode/uudecode
#uuencodes files into ASCII characters
#uudecode decodes uuencoded files
#
uuencode filename.ext filename.ext > uuencodedfile.ext
				#encodes filename.ext file and
				#saves the output into the uuencodedfile.ext file
				#

uuencode -m filename.ext filename.ext > uuencodedfile64
				#encodes filename.ext file with base64
				#format and saves the output into uuencodedfile64
				#

uudecode -o filename.ext uuencodedfile.ext
				#decodes uuencodedfile.ext and saves the 
				#output into filename.ext
				#

#mimencode
#


#openssl
#Open source Secure Sockets Layer
#

openssl aes-128-ecb -salt -in filename.ext -out encrypted.filename -pass pass:p@sSw0rD
				#encrypts filename.ext using the AES 128 bytes
				#Eliptic Curve encryption algorhythm and
				#saves it as encrypted.filename
				#

openssl aes-128-ecb -d -salt -in encrypted.filename -out filename.ext -pass pass:p@sSw0rD
				#decrypts encrypted.filename using the AES ECB 128 bytes
				#algorythm and saves the output into filename.ext
				#

tar czvf - ~/mydirectory/ | openssl des3 -salt -out encrypted_dir.tar.gz -pass pass:p@sSw0rD
				#creates an encrypted copy of ~/mydirectory/ and
				#saves it into encrypted_dir.tar.gz
				#

#shred
#removes files and overwrites their content

#mktemp
#creates a temporary file with a unique filename

mktemp				#creates a file with a random
				#name tmp + chars long string
				#

mktemp $var_name.XXXXXX		#creates a file with the name
				#stored in $var_name + six chars
				#needs at least four place holders (XXXX)

#dos2unix
#converts DOS-formatted text files (CR-LF terminated)
#into UNIX format files (LF terminated)

#ptx
#outputs a permuted index



						##########################
						#####NETWORK COMMANDS#####
						##########################

#host
#finds the IP address of a host
#using DNS
host mysite.com				#"mysite.com has address 10.11.11.10"


#ipcalc
#does a reverse DNS lookup to find
#the hostname of an IP address
#
ipcalc -h 11.10.10.11		
				#HOSTNAME=yoursite.com
				#

#nslookup
#does an internet name server lookup
#by ip address
nslookup -sil 11.10.10.11
				#nslookup mysite.com
				#server: 12.12.21.21
				#address: 12.21.12.21
				#

#dig
#makes an internet name server
#lookup on a host
dig -x 12.21.12.21		
				#10.11.11.10.in.ternet.host
				#11.10.01.11.the.isp.hostname.net
				#

#traceroute
#traces the route taken by packet
#sent to a remote host
traceroute 45.54.45.54
				#lists the IP hops made by the
				#packets sent to a host
				#

#ping
#broadcast an ICMP ECHO_REQUEST
#packet to another machine
ping localhost
				#64 bytes from localhost.localdomain
				#
#finger
#retrieves information about users
#connected to a network
finger username			
				#shows general user information
				#shell, home directory and address(?)

#ftp
#transfer files from/to a remote host(s)
#

#uucp (UNIX to UNIX copy)
#tranfers files between UNIX servers
#

#uux (UNIX to UNIX execute)
#execute commands on a remote system
#

#cu (Call Up)
#remote system to system connection
#

#wget
#downloads files or retrieves websites
wget -p http://www.website.com/file.html
				#the -p parameter or --page-requisite tells
				#wget to fetch all required files to display
				#the specified website
				#
wget -r ftp://ftp.server.net/file_folder/ -O $FOLDERNAME
				#the -r parameter tells wget to retrieve all
				#files recursively
				#
wget -c ftp://ftp.server.net/file_folder/bigzippedfile.zip
				#the -c parameter tells wget to resume
				#a download if it gets interrupted
				#

#lynx
#web and file browser
#
lynx -dump http://www.website.com/filename.html > $FILENAME
				#the -dump option tells lynx to retrieve
				#a file from a web server
				#
				#-transversal tells lynx to start crawling
				#all links in a specified URL
				#-crawl tells lynx to output the website
				#to a log file
				#

#rlogin (has security issues)
#initiates a session on a remote host
#

#rsh (has security issues)
#execute command on a remote host
#

#rcp
#copies files between different networked machines
#

#rsync
#synchronizes files between two different networked machines
#
rsync -a ~/pathto/thedirectory/*fileextension	/host-1/pathto/thedirectory/

#ssh
#allows login into a remote host
#
ssh username@hostip

#scp
#copies files between two different networked machines
#

#write
#allows terminal-to-terminal communication in the local network
#

#netconfig
#allows configuration of a network adapter
#

#mail
#allows sending/reading e-mail messages
#

#mailto
#allows sending e-mail messages from the CLI also allows MIME messages 
#



						##########################
						#####terminal control#####
						##########################

#tput
#initialize/fetch terminal information
#
tput clear
				#clears the screen
				#
tput reset			
				#resets the terminal
				#
tput cup 15 25		
				#moves the mouse to coordinates X:125 Y:250
				#

#infocmp
#prints extended information about the current terminal
#
infocmp

#clear/reset
#clear the text out of a terminal screen
#reset terminal parameters and clears the screen

#script
#records all user keystrokes in the terminal
#
script keystrokes_log.txt
                #saves pressed keystrokes into
                #keystrokes_log.txt
                #

script -a keystrokes_log.txt
                #appends the new keystrokes to
                #an existing file
                #

script -c 'command' keystrokes_log.txt
                #saves the results of a single
                #command instead a shell session
                #

script -c 'command' -q keystrokes_log.txt
                #-q tells script to hide its output
                #

script --timing=time.txt keystrokes_log.txt
                #saves time execution information
                #into the 'time.txt' file
                #

scriptreplay --timing=time.txt keystrokes_log.txt
                #scriptreplay replays the commands
                #stored in keystrokes_log.txt file
                #

exit
                #stops keystroke recording


#stty
#displays or changes the characteristics
#of the terminal
#
stty -g
				#saves terminal settings
				#

stty -F /dev/tty7
                #uses tty7 instead of stdout
                #

stty -icanon -echo
				#disables canonical/local echo modes
				#



							#######################
							#####math commands#####
							#######################


#factor
#decomposes an integer into prime factors
#
factor 25417
				#27417: 3 13 19 37
				#

#bc
#(extensible) basic calculator
#

#dc
#(extensible) desk calculator
#uses Reverse Polish Notation
#

#seq
#prints a sequence of integers
#
seq 10
				#1
				#2
				#3
				#4
				#5
				#6
				#7
				#8
				#9
				#10

seq -s : 10
				#1:2:3:4:5:6:7:8:9:10
				#

seq 50 100
				#prints all numbers between 50 and 100
				#

seq 50 5 100			
				#prints all numbers between 50 and 100
				#in increments of 5
				#

#yes
#prints the "y" character continuously
#it also allows to run command non-interactively
#
yes | fsck /dev/sda
				#the command expecting user input
				#will get it from yes instead
				#

yes | rm -r directory		
				#removes 'directory' without waiting
				#for user input
				#

yes $PATH >  verybigfile.txt
				#parsing the variable $PATH the command
				#creates a very big ASCII file
				#

#printenv
#prints environment variables set for a user
#
printenv | grep SHELL
				#shows the shell assigned to the user
				#

#mkfifo
#creates a temporary FIFO buffer for
#date transfers between processes
#
mkfifo pipe1
				#creates the named pipe "pipe1"
				#
#dd
#data duplicator command
#
dd if=filename conv=ucase > filename.ext
				#converts "filename" to all uppercase
				#

dd if=$0 of=$0.copyname	2> /dev/null
				#allows the script to copy itself
				#

keypresses=100
dd bs=1 count=$keypresses 2> /dev/null
				#captures 100 keystrokes
				#

dd if=/dev/urandom of=filename bs=1 count=7
sync
rm -f filename
				#securely deletes a file (filename)
				#fills the file with random data with a blocksize of '1'
				#seven times (count=7)
				#flushes the buffers (sync) then remove the file (rm -f filename)
				#

#od
#octal dump converts input and files
#to octal or other bases
#
head -c4 /dev/urandom | od -N4 -tu4

#hexdump
#dumps files in hexadecimal, octal or ASCII format
#
hexdump -C /bin/ls | less
				#-C formats output in tabular form
				#

#objdump
#shows information about binary/object files
#in hexadecimal or disassembled format
#
objdump -d /bin/ls
				#-d parameter shows file information
				#in disassembled mode
				#

#mcookie
#generates a random magic cookie
#of 128-bit (32 characters) length
#
mcookie
				#f3a4383d5751d693c8800fadcd71a660
				#

#m4
#macro processing filter
#combines eval, tr and awk functionalities
#


#xmessage
#X-based pop-up message windows
#


#zenity
#GTK+ dialog widget displaying utility
#


#doexec
#allows to pass arguments to an executable
#


#dialog
#tools that allow displaying interactive
#dialog boxes from a  script
#


#sox
#plays/performs sound files conversion
#
sox soundfilename.midi soundfilename.wav
				#converts soundfilename.midi into
				#a WAV file
				#

#readelf
#shows information and statistics
#about an ELF binary file
#
readelf -h filename
				#shows header file information
				#about filename
				#

#size
#shows segment sizes of an executable file
#
size filename
				#text	data	bss	dec	hex filename
				#7080	0080	680	678	98	filename	

#logger
#allows to append a user generated message
#to the system log
#
logger This is a long ass message.
				#adds the user suplied message
				#to /var/log/messages
				#

logger -t $0 -i Error after line 25.
				#-t parameter specifies the logger entry tag
				#-i records process ID
				#

#logrotate
#allows rotation, compression, deleting or emailing
#system log files
#



							#####################
							#####JOB CONTROL#####
							#####################

#ps (process statistics)
#list currently executing processes
#


#pgrep (ps + grep)
#pkill (ps + kill)
#
pgrep processname

#pstree
#lists running processes in tree format
#
pstree

#top
#display a list of processes
#
top -b
				#-b tells top to display the list in
				#text mode so it can be parsed or accessed
				#from a script
				#

#nice
#allows to manipulate a process' priority
#from 19 [lowest] to -20 [highest]
#


#nohup
#keep a process running even after
#user logs off
#


#pidof
#displays the Process ID of a running job
#
pidof processname

#fuser
#shows the processes accessing a file, set of
#files or direvtory
#
fuser -u /usr/bin/vim
				#-u parameter shows the username
				#
fuser -un tcp 25
				#-n parameter shows processes accessing a port
				#

#cron (crond)
#program scheduler
#



							#########################
							#####PROCESS CONTROL#####
							#########################


#init
#determines the runlevel of the system
#


#runlevel
#shows the current and last runlevel
#


#halt/shutdown
#shut down a system
#


#reboot
#reboots a system
#


#service
#starts/stops a system service
#


							##########################
							#####NETWORK COMMANDS#####
							##########################


#ifconfig
#network interface configuration tool
#
ifconfig -a
				#-a tells ifconfig to show
				#all network interfaces even if
				#they're down
				#

#netstat
#show network statistics
#
netstat -r
				#-r tells netstat to show the
				#routes
				#
netstat -lptu
				#-lptu tells netstat to show
				#port listening shockets and the
				#processes used by these sockets
				#

#iwconfig
#command used to configure
#wireless networks
#


#ip
#general IP network configuration tool
#


#route
#shows information or modifies kernel
#routing table
#


#iptables
#packet filtering tool mostly used
#to set up firewalls
#


#chkconfig
#check network and system configuration
#
chkconfig --list

#tcpdump
#allows to analyze network traffic
#



							####################
							#####FILESYSTEM#####
							####################



#mount
#allows a filesystem to be mounted
#


#umount
#allows to unmount filesystem
#
umount /mnt/cdrom

#sync
#forces a write of updated buffers
#to the hard drive
#


#losetup
#configures loopback devices
#


#mkswap
#creates a swap partition/file
#


#swapon/swapoff
#enable and disable swap partitions/files
#


#mkdosfs
#creates a DOS FAT filesystem
#


#hdparm
#lists or change hard disk parameters
#


#fdisk
#creates or changes the partition table
#


#fsck
#allows to check a UNIX	filesystem
#


#badblocks
#checks for bad blocks on a device
#


#lsusb
#shows all active USB buses
#


#usbmodules
#shows information about USB driver
#modules
#


#lspci
#shows present PCI buses
#


#mkbootdisk


#mkisofs


#chroot


#lockfile


#flock


#mknod


#makedev


#tmpwatch


#dump


#restore



                        ##################
                        #SYSTEM RESOURCES#
                        ##################


#quota


#setquota


#umask


#rdev



                        #################
                        #####MODULES#####
                        #################


#lsmod


#insmod


#rmmod


#modprobe


#depmod


#modinfo



                        ######################
                        #####MISCELLANEOUS#####
                        ######################


#env


#ldd


#watch


#strip


#nm


#xrand


#rdist








































'-o-o-o'
#

stat --format=%A file			#prints permissions
stat --format=%U file			#prints file/filesystem owner
stat --format=%s file			#prints file size
stat --format=%F file			#prints file type

#options combined
stat --format="%A %U %s %F" file

#byte order mark manipulation
sed '1s/^\xEF\xBB\xBF//' < orig.txt > new.txt
sed -i '1s/^\xEF\xBB\xBF//' orig.txt
# Deletes files containing these characters: + { ; " \ = ? ~ ( ) < > & * | $
badname=`echo "$filename" | sed -n /[\+\{\;\"\\\=\?~\(\)\<\>\&\*\|\$]/p` \
rm $badname 2>/dev/null
EOF