🐚 Shell Scripting Syntax Guide
This guide covers the essential shell scripting syntax you need to write powerful bash scripts. 🧠✨
📄 1. Script Declaration
Start your script with the shebang line:
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It tells the system which interpreter to use.
🧾 2. Comments
Use # for comments:
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🧮 3. Variables
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No space around =. Access with $variable.
🧠 4. Conditionals
🔸 If-Else
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🔸 Test Operators
| Operator | Meaning |
|---|---|
| [[-z string]] | Empty string |
| [[-n string]] | Not empty string |
| [[string == string]] | Equal |
| [[string != string]] | Not Equal |
| [[num -eq num]] | Equal |
| [[num -ne num]] | Not equal |
| [[num -lt num]] | Less than |
| [[num -le num]] | Less than or equal |
| [[num -gt num]] | Greater than |
| [[num -ge num]] | Greater than or equal |
| [[string =~ string]] | Regexp |
| (( num < num )) | Numeric conditions |
| [[-o noclobber]] | If OPTIONNAME is enabled |
| [[! EXPR]] | Not |
| [[X || Y]] | Or |
| [[X && Y]] | And |
🔸 File conditions
| Operator | Meaning |
|---|---|
| [[-e FILE]] | Exists |
| [[-r FILE]] | Readable |
| [[-h FILE]] | Symlink |
| [[-d FILE]] | Directory |
| [[-w FILE]] | Writable |
| [[-s FILE]] | Size is > 0 bytes |
| [[-f FILE]] | File |
| [[-x FILE]] | Executable |
| [[FILE1 -nt FILE2]] | 1 is more recent than 2 |
| [[FILE1 -ot FILE2]] | 2 is more recent than 1 |
| [[FILE1 -ef FILE2]] | Same files |
🔁 5. Loops
🔸 For Loop
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🔸 While Loop
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🔸 Until Loop
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📤 6. Functions
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📦 7. Arrays
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📂 8. File Input/Output
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💥 9. Exit Status
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0 = success, non-zero = failure
🔀 10. Case Statement
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🚫 11. Error Handling
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🔍 12. Read User Input
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🔐 13. Quotes
" ": allow variable expansion' ': literal string`or$(...): command substitution
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📌 14. Useful Shortcuts
| Shortcut | Description |
|---|---|
&& | Run next if previous success |
|| | Run next if previous fails |
$(...) | Command substitution |
${var} | Variable expansion |
"$@" | All script args |
🎯 15. Script Arguments
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✅ That’s a wrap! You now have a handy reference to shell scripting syntax!