Basic scripting is done

Bash-Scripting.txt

@@ -460,4 +460,203 @@
                             if NOT true              |
                                 |--------------------|
 
-                        
+
+-> For loops
+
+    for arg in [list]
+    do
+        command(s)..
+    done
+
+    * Example 
+        for PLANET in "Mercury Venus Earth"
+        do
+            echo $PLANET
+        done
+
+        for file in *.txt
+        do
+            $file
+        done
+
+-> For loops - C style for loops
+
+    for ((i=1; i <= 10 ; i++))
+    do
+        echo $i
+    done
+
+-> While loop
+
+    while [ condition ]
+    do
+        command(s)
+    done
+
+-> C-style While loop
+
+    while (( condition ))
+    do
+        command(s)
+    done
+
+    * Example
+        A=1
+        LIMIT=10
+        while (( A < LIMIT )) //no $ here
+        do
+            touch $A
+            let A++
+        done
+
+-> Reading Files with While loop
+
+    while read line
+    do
+        command(s)..
+    done < "$FILENAME"
+
+    cat "$FILENAME" |
+    while read line
+    do
+        echo $line
+    done
+
+-> Case:
+
+    case "$VAR" in
+
+        "$condition1")
+            command(s)...
+        ;;
+        "$condition2")
+            command(s)...
+        ;;
+        *)
+        command(s)..
+        ;;
+    esac
+
+    *Example:
+
+    case "$(whoami)" in
+
+     "root")
+            echo you are root
+            ;;
+     "richard"|"susan")
+            echo you are user
+            ;;
+     *)
+            echo I don't know you
+            ;;
+    esac
+
+-> shift 
+    It's a command to throw away the parameter count
+    that is given to the script.
+
+
+-> getopts:
+
+    * easy way how to parse short positional parameters (-f)
+    * doesn't support long positional parameters ( --help )
+    
+    * getopts optstring name
+
+    -> For examples:
+
+        #!/bin/bash
+
+        while getopts a:b:cd param; do
+         case $param in                                                     OPTIND is initialized to 1
+            a)  echo ""                                                     each time the shell or a
+                echo "parameter 'a' with argument: $OPTARG"                 shell script is invoked.
+                ;;
+            b)  echo "parameter 'b' with argument: $OPTARG"                 getopts places index of the
+                ;;                                                          next argument to be
+            c)  echo "parameter 'c' selected (no colon, no argument)"       processed into the variable
+                ;;                                                          OPTIND
+            d)  echo "parameter 'd' selected (no colon, no argument)"
+                ;;
+         esac
+        done
+
+
+-> getopt:
+
+    * parse command options (enhanced)
+
+    opts=`getopt -o a::b:cde --long file::,name::,help -- "$@"`
+    eval set -- "$opts"
+
+    #!/bin/bash
+
+    echo "All arguments: $@"
+    opts=`getopt -o a::b:cde --long file::,name:,help -- "$@"`
+    eval set -- "$opts"
+    echo "All arguments after getopt: $@"
+
+-> Arrays:
+
+    * Declaration
+        * ARRAY=(value1 value2 .. valueN)
+        * ARRAY=(one,two,three)
+
+    * Calling
+        * ${ARRAY[0]}   #one
+        * ${ARRAY[1]}   #two
+        * ${ARRAY[2]}   #three
+
+    
+    * ARRAY=(one,two,three)
+
+        ${ARRAY[0]}     #one
+        ${ARRAY[1]}     #two
+        ${ARRAY[2]}     #three
+        ${ARRAY[@]}     #all items in Arrays
+        ${ARRAY[*]}     #all items in array, delimited by first character of IFS
+        ${!ARRAY[@]}    #all indexes in the array ( @/* )
+        ${#ARRAY[@]}    #number of items in the array ( @/* )
+        ${#ARRAY[0]}    #length of item zero
+
+-> Functions
+
+    * function_name(){
+        <commands>
+      }
+
+    * function function_name{
+        <commands>
+      }
+
+    * Example
+        | function hello{
+        |     echo hello
+        | }
+        |
+        | echo "output from function hello: "
+        | hello
+
+
+
+        | function hello{
+        |     echo hello $1
+        |     return 11
+        | }
+        |
+        | echo "output from function hello: "
+        | hello richard
+        | echo "return value from function hello is: $?"
+
+
+
+        | function hello {                      function hello{
+        |   name=$1                                 local name=$1
+        |   echo "hello $name"                      echo "hello $name"
+        | }                                     }
+        |
+        | echo "enter your name:"               echo "enter your name:"
+        | read name     #richard                read name       #richard
+        | hello Peter   #hello Peter            hello Peter     #hello Peter
+        | echo $name    #Peter                  echo $name      #richard