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Linux/Bash-Script/02-Operators.md
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Linux/Bash-Script/02-Operators.md
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# 🖥️ Bash Operators
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A quick reference guide to essential bash command operators and their usage.
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---
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## `>` — **Write to File (Overwrite)**
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This operator **creates a new file** or **overwrites** the contents of an existing file.
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```bash
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echo "Hi" > file1
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```
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📄 *Creates* `file1` and writes `"Hi"` into it. If `file1` already exists, its content is replaced.
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---
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## `>>` — **Append to File**
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Adds content to the **end of an existing file** without deleting what's already there.
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```bash
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echo "Hi" >> file1
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```
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📝 *Appends* `"Hi"` to the end of `file1`.
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---
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## `&&` — **AND Operator**
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Runs the **second command only if the first succeeds**.
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```bash
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apt update && apt upgrade
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```
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🔗 `apt upgrade` runs only if `apt update` completes successfully.
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---
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## `;` — **Run Multiple Commands**
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Executes **commands sequentially**, regardless of success or failure.
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```bash
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echo "Hi" > file1 ; cat file1
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```
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🔄 Both commands are executed one after the other.
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---
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## `|` — **Pipe Operator**
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Takes the **output of the command on the left** and **uses it as input for the command on the right**.
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```bash
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ls -l | grep "txt"
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```
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🔗 Passes the output of `ls -l` to `grep "txt"` to filter and display only files containing "txt".
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---
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## `*` — **Wildcard (All Matching Files)**
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Matches **all files** that meet the pattern.
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```bash
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cat file*
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```
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🌐 Displays the contents of all files starting with `file`.
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---
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## `[ ... ]` — **Specific Character Matching**
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Reads files that match specific characters at the position defined in brackets.
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```bash
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cat file[1,2,3]
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```
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📚 Reads `file1`, `file2`, and `file3` (if they exist). Equivalent to:
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```bash
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cat file1 file2 file3
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```
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