Beginner LevelLinux Commands & SysAdmin
What are File Descriptors (0=stdin, 1=stdout, 2=stderr) and Redirection (>, >>, 2>&1)?
❓ Interview Prompt: Explain standard I/O streams (stdin, stdout, stderr), redirection operators (>, >>), and merging error streams.
In Linux, everything is treated as a file stream represented by integer File Descriptors (FD):
•
FD 0 (stdin): Standard Input (keyboard/stream input).
•
FD 1 (stdout): Standard Output (normal terminal output).
•
FD 2 (stderr): Standard Error (error diagnostic output).
Redirection Operators:
•
'> file': Overwrites stdout to a file.
•
'>> file': Appends stdout to a file.
•
'2> file': Redirects stderr to a file.
•
'2>&1': Merges stderr into stdout.
Code Implementation Example
bash
# Redirect stdout to file (overwrite)
echo "Build successful" > build.log
# Append stdout to file
echo "Timestamp: $(date)" >> build.log
# Redirect both stdout and stderr to a single log file
./deploy.sh > output.log 2>&1💡Redirecting standard output and standard error streams in Bash.
🎯 Interview Key Takeaway
Use > to overwrite output, >> to append, and 2>&1 to merge standard error into standard output.
#File Descriptors#Redirection#stdin#stdout#stderr#Beginner
Back to all Linux Commands & SysAdmin Questions→