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_posts/2023-10-07-porting-program-directives-shell-scripts.md

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+---
+title: Porting program directives into shell scripts
+tags:  bash, dash, shell, linux, interpreter, commandline, syntax
+article_header:
+  type: cover
+  image:
+    src: images/porting-program-directives-shell-scripts-01.jpg
+---
+
+## Introduction
+
+Some programs operations may include commands that can allow you to script them from your shell, such as **bash**.
+Moreover , some programs allow for a whole set of scripting capabilities within itself, but been able to ultimately chain them with some interpreter logic in order to perform some more complex actions.
+
+### Tmux case of study
+
+For instance in `tmux` terminal multiplexer for Linux, and other shell systems, the program has such a wide array of commands that customize the user experience, which can be checked on its manpage [man tmux](https://man7.org/linux/man-pages/man1/tmux.1.html)
+
+Say that I want to display a message, this command can be runned in three different places:
+    - Inside the program
+    - In the configuration file
+    - From the command line interpreter (the shell, probably **bash**)
+
+Say for the command 
+```
+display "Hello World"
+```
+
+Will show that message in the status bar of the program.
+
+Running it Inside the program would be
+
+```
+:display "Hello World"
+```
+
+Running it from its config file `$HOME/.tmux.conf` just append on it the following line.
+
+```
+display "Hello World"
+```
+
+In order to run it from the shell you need to just append the `tmux` to it and it will be runned.
+Ommitting some program specific particularities the former command can be runned as
+
+```
+$ tmux display "Hello World"
+```
+
+This opens up a whole new dimension of scripting capabilities by hooking up shell scripts performing program calls in and out, creating some more complex form of logic and functionalities.
+
+
+### A syntax colission
+
+Been `tmux` a complex program itself, the commands can be taking quite sophisticated forms that can collide with the syntax of shell.
+Let's take the example of the `tmux` command `bind-key` which can bind to certain key-presses some actions.
+Simplified and in a nutshell the command can be explained as
+```
+bind-key <key> <command01> /; <command02> /; ... /; <commandn>
+```
+So say I do
+
+```
+bind-key a display -p "Hello" \; display -p "World"
+```
+
+That would be working from Inside the program , and in its configuration file, but as soon as you try to execute it in the shell
+
+```
+$ tmux bind-key a display -p "Hello" \; display -p "World"
+World
+```
+
+And by pressing a , I will only get the "Hello" message
+The reason being is that the shell is "swallowing" the `\;` characters , saying , \ for escape the next character, ; for sequencing the execution of the commands.
+Thats why it prints then "World" to stdout
+
+One way of solving this situation is to escape these succession of characters by quoting them , according to `man bash` *Quoting  is  used  to remove the special meaning of certain characters or words to the shell.*. So that is our ally
+
+```
+tmux bind-key a display -p "Hello" '\;' display -p "World"
+```
+
+Will be the command corrected now
+
+### List of conflicting characters
+
+As you can see, you need to be careful with what the shell can interpret, in terms of characters telling the shell to perform a certain expanwould sion, or to escape some characters etc...
+
+Doing a 'man bash' checking for different expansions and etc... having an in-depth understanding of those rules would be the ultimate objective giving you a clear understanding on what conflicts may arise on such a "translation", but in a nutshell It is important to pay attention to the following characters.
+
+- Quotes : Single (') and double (")
+- Escape characters: Such as the backslash ('\')
+- Semicolon (;)
+- Ampersand (&)
+- Pipe (|)
+- Dollar Sign ($)
+- Parentheses (()) and Curly Braces ({})
+- Brackets ([]) and Wildcards (*, ?, [])
+- Whitespaces
+- Quotes in Quotes:
+- Hashtags for Comments #.
+