style-guide: document use of POSIX-compliant shell syntax in subdirectory common

contributing-guides/style-guide.md

@@ -364,7 +364,7 @@
 Short option mnemonics are optional hints which can be added to help users understand the meaning of these short options. The assigned mnemonics should match with the ones in the command's official documentation (e.g. from `man` or `Get-Help`). For example:
 
 ```md
 - [d]isplay the ins[t]allation [i]D for the current device. Useful for offline license activation:
 
 `slmgr.vbs /dti`
 
@@ -376,11 +376,11 @@
 Note that, in the first example, the `[d]`, `[t]`, and `[i]` characters are enclosed with square brackets to indicate that the `/dti` option of the command is a combination of "display", "installation", and "ID", respectively. 
 Group consecutive mnemonic characters under the same square brackets, for example: `e[xp]i[r]ation` instead of `e[x][p]i[r]ation`.
 
 **Mnemonic characters must be written in a case-sensitive manner**, even when it is placed as the first character of the sentence (i.e. use `[d]isplay` instead of `[D]isplay`).
 This is to avoid conflicts with GNU-style command options which may interpret uppercase options differently than the lowercase ones, such as `-v` for displaying the command's `[v]ersion` number and `-V` to run the command in `[V]erbose` mode.
 
 Option mnemonics may also be used in translations as long as the highlighted word contains similar meanings to the language (commonly English) which the command is written for.
 For example, `[d]ownload` in English may be translated into `[d]escargar` in Spanish, `[i]nstall` in English may be translated to `[i]nstallieren` in German, and `[a]pp` in English may be translated into `[a]plikasi` in Indonesian and Malay.
 
 - Optionally, mnemonics and their enclosed terms can be separated with brackets from the rest of the description (i.e. `([a]ll)`) in translations and specific pages to provide additional context or mention a word not present in the description.
 
@@ -390,6 +390,26 @@
 
 ## Example commands
 
+### POSIX-compliant syntax
+
+- The examples of pages in the subdirectory `common` for UNIX-like operating systems (e.g. `pages/common/tar.md`), preferably, should be written with the shell syntax specified by the [latest POSIX standard](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18).
+However, if you believe the example is hard to read, has little to no use, or is impossible to write in POSIX-compliant syntax, use non-POSIX syntax and add a note or warning indicating it and some or all of its consequences concisely and specifically. For example:
+
+  ```md
+  # IFS
+
+  > IFS (Internal Field Separator) is a special environment variable that defines the delimiter used for word splitting in Unix shells.
+  > The default value of IFS is a space, tab, and newline. The three characters serve as delimiters.
+  > Note: Not all shells support ANSI C quoted strings (i.e., $'...' and $"..."), the dollar sign could be included in the string.
+  > More information: <https://www.gnu.org/software/bash/manual/html_node/Word-Splitting.html>.
+  ```
+
+  To help you decide using POSIX-compliant syntax, ask yourself this:
+
+  - Is the example too long (i.e. [exceeds the maximum line length](https://github.com/tldr-pages/tldr/blob/main/.markdownlint.json#L5))?
+  - Does the example utilize any [risky](https://unix.stackexchange.com/a/278439) or [inefficient](https://unix.stackexchange.com/a/169765) commands?
+  - Does the example return the correct output?
+
 ### Option syntax
 
 - For commonly/frequently used commands (e.g. `grep`, `tar`, `etc`), we prefer using short options along with [mnemonics](#short-option-mnemonics) or both inside a placeholder.
@@ -550,7 +570,7 @@
 | Image (as means of storage, such as CD, ISO, and Docker) | Image | Another recommended word, [`citra`](https://kbbi.kemdikbud.go.id/entri/citra), is not officially recognized for computing. |
 | Initialize, Reinitialize | Inisialisasikan, Inisialisasikan Ulang | The word [`inisialisasi`](https://kbbi.kemdikbud.go.id/entri/inisialisasi) is officially considered as noun. Requires a `-kan` suffix to convert into a verb. |
 | Interpreter | Interpreter | Preferred over [`penerjemah`](https://kbbi.kemdikbud.go.id/entri/penerjemah) which is also commonly used to describe `translator`. |
 | Install, Reinstall | Pasang, Pasang Ulang | Preferred over `instal` [which is not considered a standard word](https://kbbi.kemdikbud.go.id/entri/instal). |
 | Load, Reload | Muat, Muat ulang | These words are the same for `boot` and `reboot`. See notes in the bottom section. |
 | Options / Preferences (macOS) / Settings | Pengaturan | Preferred over [`opsi`](https://kbbi.kemdikbud.go.id/entri/opsi). |
 | Server | Server | Preferred over [`peladen`](https://kbbi.kemdikbud.go.id/entri/peladen) or [`pelayan`](https://kbbi.kemdikbud.go.id/entri/pelayan), which are less common when used in computing contexts. |
@@ -571,7 +591,7 @@
 
 Add detailed contexts to remove ambiguity (notice the highlighted word):
 
 > Muat konfigurasi dari file yang ditentukan setelah **pengguna** memuat ulang **sistem operasi**
 
 Similarly, for the word `start` / `mulai`