exit codes

Linux/Bash Script/3-Exit-Codes.md

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+# 🧾 Linux Exit Codes Cheat Sheet
+
+Every command in Linux returns an **exit status code** upon completion. You can check this code using:
+
+```bash
+command
+echo $?
+```
+
+These codes are helpful for debugging scripts or understanding command behavior.
+
+---
+
+## ✅ Common Exit Codes & Their Meanings
+
+| Exit Code | Meaning                                         |
+| --------- | ----------------------------------------------- |
+| `0`       | ✅ Success                                       |
+| `1`       | ❌ General Error                                 |
+| `2`       | ⚠️ Misuse of Shell Built-in (bad options, etc.) |
+| `126`     | 🚫 Command Found but Cannot Execute             |
+| `127`     | ❓ Command Not Found                             |
+| `130`     | ⌨️ Terminated by `Ctrl+C`                       |
+| `137`     | 💀 Killed (e.g., `kill -9`)                     |
+
+---
+
+## 🔍 Exit Code Examples
+
+### `0` — Success
+
+```bash
+echo "Hello"
+echo $?    # ➜ 0
+```
+
+---
+
+### `1` — General Error
+
+```bash
+grep "text" non_existing_file.txt
+echo $?    # ➜ 1
+```
+
+---
+
+### `2` — Misuse of Shell Built-in
+
+```bash
+ls --wrongoption
+echo $?    # ➜ 2
+```
+
+---
+
+### `126` — Command Found but Not Executable
+
+```bash
+touch myscript.sh
+chmod -x myscript.sh
+./myscript.sh
+echo $?    # ➜ 126
+```
+
+---
+
+### `127` — Command Not Found
+
+```bash
+nonexistentcommand
+echo $?    # ➜ 127
+```
+
+---
+
+### `130` — Script Terminated by `Ctrl+C`
+
+```bash
+sleep 10
+# Press Ctrl+C while it sleeps
+echo $?    # ➜ 130
+```
+
+---
+
+### `137` — Killed by `kill -9`
+
+```bash
+sleep 100 &
+kill -9 $!
+wait
+echo $?    # ➜ 137
+```
+