Bash

# Bash Synx
var1 = 3                              #variable assignment
var2 = "Test"                         #variable assignment
echo $var1                            #print a var
$?                                    #Stores the exit value of the last command that was executed.
" "                                   #ignore whitespace, count all as one arg or string
' '                                   #ignore special characters
` `                                   #use result of a command executed between back-ticks
int1 -eq int2                         #Returns True if int1 is equal to int2.
int1 -ge int2                         #Returns True if int1 is greater than or equal to int2.
int1 -gt int2                         #Returns True if int1 is greater than int2.
int1 -le int2                         #Returns True if int1 is less than or equal to int2
int1 -lt int2                         #Returns True if int1 is less than int2
int1 -ne int2                         #Returns True if int1 is not equal to int2
str1 = str2                           #Returns True if str1 is identical to str2.
str1 != str2                          #Returns True if str1 is not identical to str2.
str                                   #Returns True if str is not null.
-n str                                #Returns True if the length of str is greater than zero.
-z str                                #Returns True if the length of str is equal to zero (zero is not null!)
-d filename                           #Returns True if file, filename is a directory.
-f filename                           #Returns True if file, filename is an ordinary file.
-r filename                           #Returns True if file, filename can be read by the process.
-s filename                           #Returns True if file, filename has a nonzero length.
-w filename                           #Returns True if file, filename can be written by the process.
-x filename                           #Returns True if file, filename is executable.
!expression                           #Returns true if expression is not true
expr1 -a expr2                        #Returns True if expr1 and expr2 are true. ( && , and )
expr1 -o expr2                        #Returns True if expr1 or expr2 is true. ( ||, or )
arr1=(val1 val2 ...)                  #arrays
arr1[2]                               #retrieve second element