01-redirection-pipes.md

Day 10 – Redirection & Pipes

Topics Covered:

• Output/input redirection: >, >>, <, 2>, &>, tee
• Pipes: |
• Command chaining: ;, &&, ||
• Use cases: logs, backups, chaining scripts

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Key Notes:

• > : Redirects standard output (stdout) to a file (overwrites).

• >> : Appends output to a file without overwriting.

• < : Takes input from a file.

• 2> : Redirects standard error (stderr) to a file.

• &> : Redirects both stdout and stderr to a file.

• tee : Displays output and writes it to a file at the same time.

• | : Takes the output of one command and passes it as input to another (pipe).

• Command chaining:

  • ; : Run multiple commands one after another, regardless of success.
  • && : Run the next command only if the previous one is successful.
  • || : Run the next command only if the previous one fails.

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Commands Practiced:

# Redirect output to a file (overwrites)
echo "Hello Linux" > file.txt

# Append output to a file
echo "Another line" >> file.txt

# Redirect input from a file
cat < file.txt

# Redirect error to a file
ls wrongfile 2> error.log

# Redirect both output and error
ls /etc /fake  &> all_output.txt

# Use tee to show and write
ls /etc | tee output.txt

# Use pipe to pass output
ps aux | grep ssh

# Command chaining
mkdir test && cd test && touch file.txt
mkdir folder1 || echo "Folder creation failed"
echo "Done"; echo "Next step"

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