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--- bash_notes [2022/01/04 22:00] – [echo a string with multiple spaces] raju
+++ bash_notes [2023/12/28 08:49] (current) – [other pages in this wiki] raju
@@ Line 1: / Line 1: @@
+===== tasks =====
+==== dummy ====
+  * [[list files within a specific range]]
 ===== dummy =====
+==== other pages in this wiki ====
+  * [[bash scripting]]
+  * [[shell scripting notes]]
 ==== useful links ====
-  * https://mywiki.wooledge.org/ArithmeticExpression - Arithmetic Expansion
+  * https://explainshell.com/ - useful for understanding complex shell commands
+  * https://mywiki.wooledge.org/ArithmeticExpression - Arithmetic Expansion
+  * https://misc.flogisoft.com/bash/tip_colors_and_formatting - escape characters, color prompts, echo colored strings
+  * http://ezprompt.net/ - Easy bash prompt generator
+==== documentation links ====
+  * ignoredups, erasedups - https://www.gnu.org/software/bash/manual/html_node/Bash-Variables.html search for ignoredups .
+==== what is the difference between "ls > dirlist 2>&1" and "ls 2>&1 > dirlist"? ====
+The command
+<code>
+ls > dirlist 2>&1
+</code>
+directs both standard output (file descriptor 1) and standard error (file descriptor 2) to the file dirlist, while the command
+<code>
+ls 2>&1 > dirlist
+</code>
+directs only the standard output to file dirlist, because the standard error was made a copy of the standard output before the standard output was redirected to dirlist.
+To conclude, the order of redirections is significant.
+Ref:- https://www.gnu.org/software/bash/manual/html_node/Redirections.html -> 5th paragraph.
 ===== getopts =====
 ==== useful articles ====
@@ Line 113: / Line 143: @@
       * check if a number is greater than something
       * compare numbers
+==== add an element to an array ====
+<code>
+appliances=("AC" "TV" "Mobile" "Fridge" "Oven" "Blender")
+appliances+=("Dish Washer")
+for appliance in "${appliances[@]}"
+do
+     echo $appliance
+done
+</code>
+<code>
+languages=("PHP" "MySQL" "Bash" "Oracle")
+languages[${#languages[@]}]="Python"
+for language in "${languages[@]}"
+do
+     echo $language
+done
+</code>
+<code>
+fruits=("Banana" "Mango" "Watermelon" "Grape")
+fruits=(${fruits[@]} "Jack Fruit")
+for fruit in "${fruits[@]}"
+do
+     echo $fruit
+done
+</code>
+<code>
+men=("John" "Watson" "Micheal")
+women=("Lisa" "Ella" "Mila")
+people=(${men[@]} ${women[@]})
+for person in "${people[@]}"
+do
+     echo $person
+done
+</code>
+Ref:-
+  * https://linuxhint.com/bash_append_array/ - well written but the information density is low. So I just summarized the points here and renamed the variables a bit.
+  * https://stackoverflow.com/questions/1951506/add-a-new-element-to-an-array-without-specifying-the-index-in-bash