Autosave: 2023-02-07 08:44:16

.gitignore

@@ -1 +1,2 @@
 .DS_Store
+.obsidian/

Logic/Propositional_logic/Boolean_functions.md

@@ -19,7 +19,7 @@ Here is a work through where $f(1, 0, 1)$:
 - The second disjunction: $x \land y$ is false because $x$ is 1 and $y$ is 1
 - The overall function returns false because the main connective is disjunction and both of its disjuncts are false
 
-We can compute all possible outputs of the function by constructing a [truth table](/Logic/Propositional_logic/Truth-tables.md) with each possible variable as the truth conditions and the output of the function as the truth value:
+We can compute all possible outputs of the function by constructing a [trkjuth table](/Logic/Propositional_logic/Truth-tables.md) with each possible variable as the truth conditions and the output of the function as the truth value:
 
 | $x$ | $y$ | $z$ | $f(x,y,z) = (x \land y) \lor (\lnot(x) \land z )$ |
 | --- | --- | --- | ------------------------------------------------- |

Programming_Languages/Shell/Bash_snippets/Read_input_file_line_by_line.md

@@ -0,0 +1,12 @@
+---
+categories:
+  - Programming Languages
+tags:
+  - shell
+---
+
+# Read an input file line by line
+
+```bash
+# Add snippet here
+```

Programming_Languages/Shell/Lists_and_arrays.md

@@ -59,6 +59,18 @@ done
 
 Note that `@` here is a special symbol standing for all the members of the `words` array.
 
+### Sorting arrays
+
+#### Sorting an integer array highests to lowest
+
+```bash
+sorted_array=($(echo "${array[@]}" | tr " " "\n" | sort -nr))
+```
+
+Where `array` is the name of the original array. The sorted array will be stored in the `sorted_array` array.
+
+The `sort` command sorts the input in reverse numerical order (`-n` for numerical sort and `-r` for reverse sort). The `tr` command is used to convert the spaces in the array to newline characters so that each element is sorted on a separate line.
+
 ## Looping through file system
 
 The following script loops through all files in a directory that begin with `l` and which are of the bash file type (`.sh`) :

Programming_Languages/Shell/Read.md

@@ -7,9 +7,11 @@ tags:
 
 # `read`
 
-`read` is primarily used to capture `stdin` from the user and automatically parse it as variables. It has a secondary use case as a command that the `stdout` is piped to. This enables you to capture the output of a command as one or more variables which you can then execute subsequent operations on.
+The primary use of `read` is to capture user input from `stdin`. It is also often used frequently to parse strings or files that are redirected to it (with `<` and `<<`) or piped to it. In each case, what is read is stored as a variable.
 
-## `stdin`
+`read` will parse line by line using a space (`\n`) as the default delimiter. You can use IFS to parse by other characters and/or [split the contents into an array](/Programming_Languages/Shell/Split_into_array.md).
+
+## Example of capturing user input
 
 ```bash
 $ read var1 var2
@@ -20,8 +22,37 @@ $ bishop
 
 > If you don't specify variables, `read` will automatically parse using whitespace
 
-## `stdout`
+## Example of piping to `read`
+
+This reads the files in a directory and passes the file names to `read`.
 
 ```bash
 find -type -f  -not -path "./.git/" | read $fname
 ```
+
+## Example of parsing a file
+
+We will typically read from a source and then do something with each variable that `read` returns, e.g:
+
+```bash
+while read var; do
+  if [var == 'something']; then
+    # do something
+done < './input-file.txt
+```
+
+## `$REPLY`
+
+If you do not assign a variable name to store the value that `read` reads a default (`$REPLY`) is applied. You can reference this value in your code.
+
+For example the following loop does something if `$REPLY` is equal to an empty string:
+
+```bash
+while read;
+do
+    ((count++))
+    if [[ -z "$REPLY" ]]; then
+        echo "$count"
+    fi
+done < "$input
+```

_meta/Topic_Log.md

@@ -5,13 +5,15 @@
 - 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`
+- ~~What the weird variable symbols mean like errors and stuff~~
+- ~~Read up properly about `find` and `read`~~
 - `.list` file extension
 - Error handling
-- Splitting strings
+- ~~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
 

node-scratch.js

@@ -1,7 +0,0 @@
-process.stdin.on("data", (data) => {
-  process.stdout.write(data.toString().trim());
-  process.exit();
-});
-
-process.stdout.write("\n What is your name? \n");
-process.stdout.write(` \n > `);