Autosave: 2023-03-05 08:02:49

Programming_Languages/Shell/Data_types_in_Bash.md

@@ -0,0 +1,41 @@
+---
+categories:
+  - Programming Languages
+tags:
+  - shell
+  - data-types
+---
+
+# Data types in Bash
+
+> There is no typing in Bash
+
+- Bash variables do not have types thus bash is neither loosely or strictly typed. Anything you apply the identity operator against becomes a character string variable.
+- Bash is however able to distinguish numerical strings which is why arithmetic operations and comparisons work.
+- Consequently there is no `null` type either. The closest thing is an empty string, i.e. `APPROX_NULL=""` .
+
+## Declarations
+
+You can achieve a sort of typing through the `declare` keyword, although bear in mind this is not enforced and you do not have to use it.
+
+### `-r` : readonly
+
+```bash
+declare -r var1="I'm read only"
+```
+
+Roughly equivalent to a `const` : if you attempt to change the value of `var1` it will fail with an error message.
+
+### `i` : integer
+
+```bash
+declare -i var2="43"
+```
+
+The script will treat all subsequent occurrences of `var2` as an integer
+
+### `a` : array
+
+```bash
+declare -a anArray
+```

Programming_Languages/Shell/Loops_in_bash.md

@@ -7,9 +7,21 @@ tags:
 
 # Loops in bash
 
+## Loop through an array
+
 ```bash
 for element in "${arr[@]}"
 do
     echo "$element"
 done
 ```
+
+## Traditional for loop with upper and lower increment range
+
+```bash
+for (( i=0; i<=5;i++  )); do
+  echo $i
+done
+
+# 1 2 3 4 5
+```

Programming_Languages/Shell/Variables_and_data_types.md

@@ -7,22 +7,14 @@ tags:
 
 ## Types
 
-> There is no typing in bash!
-
-- Bash variables do not have types thus bash is neither loosely or strictly typed. Anything you apply the identity operator against becomes a character string variable.
-- Bash is however able to distinguish numerical strings which is why arithmetic operations and comparisons work.
-- Consequently there is no `null` type either. The closest thing is an empty string, i.e. `APPROX_NULL=""` .
-
 ## Variables
 
-### Variables that hold character strings
+We use the equality symbol to create a variable:
-
-As noted we use the equality symbol to create a variable:
 
 ```bash
-PRIM_VAR_STR="My first variable"
+stringVar="My first variable"
-PRIM_VAR_FLOAT="50.3"
+floatVar="50.3"
-PRIM_VAR_BOOL="true"
+boolVar="true"
 ```
 
 As there is no typing in bash, the names of these variables are purely notional.
@@ -30,36 +22,15 @@ As there is no typing in bash, the names of these variables are purely notional.
 To invoke a variable we use special brackets:
 
 ```bash
-echo ${PRIM_VAR_STR} # My first variable
+echo ${stringVar} # My first variable
-echo ${PRIM_VAR_FLOAT} # 50.3
+echo ${floatVar} # 50.3
-echo ${PRIM_VAR_BOOL} # true
+echo ${boolVar} # true
 ```
 
-- there is no compunction to use capitals for variables but it can be helpful to distinguish custom variables from program variables (see below)
+- Quotation marks at declaration are also not strictly necessary however they can help avoid bugs. Also serves as a reminder that every type is basically a string at the end of the day
-- quotation marks at declaration are also not strictly necessary however they can help avoid bugs. Also serves as a reminder that every type is basically a string at the end of the day
 
-## Declarations
+## Parameter expansion
 
-You can achieve a sort of typing through the `declare` keyword, although bear in mind this is not enforced and you do not have to use it.
+// TODO: What is the difference betweeen `$var`, `${var}` and `"${var}"` ?
 
-### `-r` : readonly
+Still not very clear on this.
-
-```bash
-declare -r var1="I'm read only"
-```
-
-Roughly equivalent to a `const` : if you attempt to change the value of `var1` it will fail with an error message.
-
-### `i` : integer
-
-```bash
-declare -i var2="43"
-```
-
-The script will treat all subsequent occurrences of `var2` as an integer
-
-### `a` : array
-
-```bash
-declare -a anArray
-```

_meta/Topic_Log.md

@@ -22,18 +22,9 @@
 
 ## Bash
 
-- Best way to run a command in a script - is it to `echo` it?
-- How to handle the return value of a command
-  - If it returns multiple values, how to isolate and loop through them
-- ~~What the weird variable symbols mean like errors and stuff~~
-- ~~Read up properly about `find` and `read`~~
-- `.list` file extension
-- Error handling
-- ~~Splitting strings~~
 - Awk
   - https://dane-bulat.medium.com/the-awk-programming-language-an-introduction-7035d343cd30
 - Why do we have to do `"$var"` instead of `$var` or `${var}` at times
-- The `test` program (does it actually use the word 'test' or is this implicit?) and its use of `-z` and and `-e` flags
 
 ## Linux