### String Comparisons:

——————————— = compare if two strings are equal != compare if two strings are not equal -n evaluate if string length is greater than zero -z evaluate if string length is equal to zero

= is equal to – if [ “$a”= “$b” ]

== is equal to -f if [ “$a”==”$b” ]

!= is not equal to if [ “$a” !=”$b” ] < is less then ,in ASCII alphabetical order if [[“$a” < “$b”]]

> is greater than, in ASCII alphabetical order if [[ “$a” > “$b”]]

-z string is null, that is has zero length

Examples: [ s1 = s2 ] (true if s1 same as s2, else false) [ s1 != s2 ] (true if s1 not same as s2, else false) [ s1 ] (true if s1 is not empty, else false) [ -n s1 ] (true if s1 has a length greater then 0, else false) [ -z s2 ] (true if s2 has a length of 0, otherwise false) Number Comparisons: ————————————

-eq is equal to if [ “$a” -eq “$b” ]

-ne is not equal to if [ “$a” -ne “$b” ]

-gt is greater than if [ “$a” -gt “$b” ]

-ge is greater than or equal to if [ “$a” -ge “$b” ]

-lt is less than if [ “$a” -lt “$b” ]

-le is less than or equal to if [ “$a” -le “$b” ] < is less than ((“$a”<“$b” ))

<= is less than or equal to ((“$a” <= “$b”))

> is greater than [“$a” > “$b”]

>= is greater than equal to [“$a” >= “$b”]

-eq compare if two numbers are equal -ge compare if one number is greater than or equal to a number -le compare if one number is less than or equal to a number -ne compare if two numbers are not equal -gt compare if one number is greater than another number -lt compare if one number is less than another number Examples: [ n1 -eq n2 ] (true if n1 same as n2, else false) [ n1 -ge n2 ] (true if n1greater then or equal to n2, else false) [ n1 -le n2 ] (true if n1 less then or equal to n2, else false) [ n1 -ne n2 ] (true if n1 is not same as n2, else false) [ n1 -gt n2 ] (true if n1 greater then n2, else false) [ n1 -lt n2 ] (true if n1 less then n2, else false)

BASH command output to the variable

# Command Substitution Syntax:

variable=$(command [option…] argument1 arguments2 …)

variable=$(/path/to/command)

variable=`command [option…] argument1 arguments2 …`

variable=`/path/to/command`