docs: Rewrite and enhance 'wait' command chapter

ebook/en/content/046-the-curl-command.md

@@ -1,30 +1,48 @@
 # The `curl` command
 
-In linux, `curl` is a tool to transfer data from or to a server, using one of the supported protocols(DICT, FILE ,FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET and TFTP).
+In Linux, curl is a powerful command-line tool used to transfer data from or to a server using a wide variety of protocols, including HTTP, HTTPS, and FTP. It is often used for testing APIs, downloading files, and automating web-related tasks.
 
-## Example :
+## The syntax of the `curl` command :
 
 ```bash
-$ curl example.com
+$ curl [options...] <url>
 ```
-
 The command will print the source code of the example.com homepage in the terminal window.
 
-## The syntax of the `curl` command is :
+## Common Options :
+
+curl has over 200 options! Here are some of the most common and useful ones.
+
+| Option               | Long Version        | Description                                                            |
+|----------------------|---------------------|------------------------------------------------------------------------|
+| `-O`                 | `--remote-name`     | Downloads the file and saves it with the same name as the remote file.  |
+| `-o <file>`          | `--output <file>`   | Saves the downloaded output to a specific filename.                    |
+| `-L`                 | `--location`        | Follows redirects if the server reports that the requested page has moved. |
+| `-X <METHOD>`        | `--request <METHOD>`| Specifies the HTTP request method to use (e.g., POST, PUT, DELETE).     |
+| `-H <header>`        | `--header <header>` | Allows you to add a custom HTTP header to your request.                 |
 
-```bash
-$ curl [options...] <url>
-```
 
-## Options :
+## Examples :
 
-Options start with one or two dashes. Many of the options require an additional value next to them.
+### 1. View the source code of a webpage
 
-The short "single-dash" form of the options, `-d` for example, may be used with or without a space between it and its value, although a space is a recommended separator. The long "double-dash" form, `-d`, `--data` for example, requires a space between it and its value.
+This is the simplest use of curl. It will fetch the content from the URL and print its HTML source code directly to your terminal.
+```bash
+$ curl example.com
+```
+### 2. Download a file
+
+The -O flag is used to download a file. curl will save it in your current directory using the same name as the remote file.
 
-Short version options that don't need any additional values can be used immediately next to each other, like for example you can specify all the options `-O`, `-L` and `-v` at once as `-OLv`.
+```bash
+$ curl -O https://github.com/bobbyiliev/101-linux-commands/archive/refs/tags/v1.0.zip
+```
+### 3. Download a file and rename it
 
-In general, all boolean options are enabled with `--option` and yet again disabled with `--no-option`. That is, you use the exact same option name but prefix it with `no-`. However, in this list we mostly only list and show the `--option` version of them. (This concept with `--no` options was added in 7.19.0. Previously most options were toggled on/off through repeated use of the same command line option.)
+Using the -o flag, you can specify a new name for the downloaded file.
+```bash
+$ curl -o linux-commands.zip https://github.com/bobbyiliev/101-linux-commands/archive/refs/tags/v1.0.zip
+```
 
 ## Installation:
 

ebook/en/content/121-the-wait-command.md

@@ -1,27 +1,76 @@
 # The `Wait` commands
 
-It is a command that waits for completing any running process of given id. if the process id is not given then it waits for all current child processes to complete.
+The wait command is a shell builtin that pauses script execution until a specific background process, or all running child processes, have finished.
 
-## Example
+Its primary purpose is to synchronize tasks, ensuring that a script doesn't continue to the next step until prerequisite background jobs are complete. A background process is a command that is run with an ampersand (&) at the end, which tells the shell to run it without waiting for it to finish.
 
-This example shows how the `wait`  command works : <br />
+## Syntax
 
-**Step-1**:
+```bash
+$ wait [PID]
+```
+[PID] - An optional Process ID to wait for. If no PID is given, wait will wait for all active child processes to complete.
 
-Create a file named "wait_example.sh" and add the following script to it.
+## Examples
 
-```
+### 1. Waiting for a Specific Process
+This example shows how to launch a single background process and wait for it specifically.
+
+### Script:
+```bash
 #!/bin/bash
-echo "Wait command" &
+echo "This process will run in the background..." &
 process_id=$!
+
+echo "Script is now waiting for process ID: $process_id"
 wait $process_id
-echo "Exited with status $?"
+echo "Process $process_id has finished."
+echo "The script exited with status: $?"
 ```
+### Explanation:
 
-**Step-2**:
+* &: The ampersand runs the echo command in the background, allowing the script to immediately continue to the next line.
 
-Run the file with bash command.
+* $!: This is a special shell variable that holds the Process ID (PID) of the most recently executed background command. We save it to the process_id variable.
 
-```
+* wait $process_id: This is the key command. The script pauses here until the process with that specific ID is complete.
+
+* $?: This variable holds the exit status of the last command that finished. An exit status of 0 means success.
+
+
+### Output:
+
+```bash
 $ bash wait_example.sh
+Script is now waiting for process ID: 12345
+This process will run in the background...
+Process 12345 has finished.
+The script exited with status: 0
 ```
+
+### 2. Waiting for All Background Processes
+This is the most common use case. Here, we launch several background tasks and then use a single wait command to pause until all of them are done.
+
+### Script:
+```bash
+#!/bin/bash
+
+echo "Starting multiple background jobs..."
+sleep 3 &
+sleep 1 &
+sleep 2 &
+
+echo "Waiting for all sleep commands to finish."
+wait
+echo "All jobs are done. Continuing with the rest of the script."
+```
+
+### Output:
+
+```bash
+$ bash wait_all_example.sh
+Starting multiple background jobs...
+Waiting for all sleep commands to finish.
+(after about 3 seconds)
+All jobs are done. Continuing with the rest of the script.
+```