In cloud infrastructure and DevOps, configuration files (YAML, JSON, INI, Nginx configs) and server logs are plain text. Being able to edit files directly inside a remote shell and parse gigabytes of log output with grep, find, sed, and awk is a required engineering skill.
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1. Terminal Text Editors: nano vs. vim
When you SSH into a remote Linux server or enter a container, there is no VS Code GUI. You must use a terminal-based editor:
nano — The Beginner-Friendly Editor
nano is intuitive and displays keyboard shortcuts at the bottom of the screen (^ represents the Ctrl key):
bash
nano /etc/nginx/nginx.conf
- Ctrl + O — WriteOut (Save) changes. Press Enter to confirm filename.
- Ctrl + W — Where Is (Search) for text.
- Ctrl + K — Cut line.
- Ctrl + U — Paste (Uncut) line.
- Ctrl + X — Exit nano (prompts to save if modified).
vim — The Ubiquitous Powerhouse
vim (Vi IMproved) is pre-installed on virtually every Linux distribution and container base image. It is a modal editor:
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Essential vim Cheat Sheet:
- Open a file:
vim app.config(starts in Normal Mode). - Start typing: Press i to switch to Insert Mode.
- Stop typing / return to command mode: Press Esc.
- Save and Exit:
:w— Save (Write).:q— Quit.:wqorZZ— Save and Quit.:q!— Force Quit (Discard all unsaved changes).
- Navigation & Editing in Normal Mode:
dd— Delete (cut) current line.yy— Copy (yank) current line.p— Paste below cursor.u— Undo last change.Ctrl + r— Redo undone change./keyword— Search forkeywordforward (pressnfor next match).:%s/old/new/g— Find and replace all occurrences across entire file.:set number— Display line numbers.
2. Searching File Contents with grep
grep (Global Regular Expression Print) scans files or standard input for text patterns:
bash
# Basic case-sensitive search
grep "ERROR" /var/log/syslog
# Case-insensitive search (-i)
grep -i "database connection failed" app.log
# Recursive directory search (-r) with line numbers (-n)
grep -rn "API_SECRET_KEY" ./src/
# Invert match (-v): Print all lines that DO NOT match
grep -v "^#" /etc/ssh/sshd_config # Show config ignoring comment lines (#)
grep -v "^$" /etc/ssh/sshd_config # Show config ignoring empty lines
# Search using Extended Regular Expressions (-E)
grep -E "(404|500|502)" /var/log/nginx/access.log
# Context lines: Show 2 lines Before (-B), After (-A), or Both (-C)
grep -C 3 "FATAL EXCEPTION" /var/log/app.log
# Print ONLY matching text (-o) and count occurrences (-c)
grep -c "GET /api/v1/checkout" access.log
3. Locating Files with find
While grep searches inside files, find searches the filesystem for files by attributes:
bash
# Find files by name (case-sensitive)
find /etc -name "nginx.conf"
# Find files by name pattern (case-insensitive -iname)
find . -iname "*.yaml"
# Find only Directories (-type d) or Regular Files (-type f)
find /var/log -type f -name "*.log"
# Find files modified in the last 24 hours (-mtime -1) or older than 7 days (+7)
find /tmp -type f -mtime +7
# Find files larger than 100MB (-size +100M)
find /var -type f -size +100M
# Find files with specific permissions
find ~/.ssh -type f -perm 600
# Execute a command on every found file (-exec ... {})
# Automatically compress logs older than 30 days:
find /var/log/apps -type f -name "*.log" -mtime +30 -exec gzip {} \;
# Delete temporary socket files safely
find /tmp -type s -name "*.sock" -delete
4. Stream Editing with sed
sed (Stream Editor) modifies text streams on the fly without opening an editor:
bash
# Replace 'localhost:5432' with 'postgres-db:5432' in output stream
sed 's/localhost:5432/postgres-db:5432/g' config.env
# In-place file modification (-i flag) — updates the file directly on disk!
sed -i 's/DEBUG=true/DEBUG=false/g' .env
# In-place modification with automatic backup creation
sed -i.bak 's/PORT=3000/PORT=8080/g' .env
# Delete lines matching a pattern
sed -i '/^#/d' config.ini # Delete all comment lines
sed -i '/^$/d' config.ini # Delete all blank lines
5. Column Extraction & Analysis with awk
awk is a complete pattern-scanning and text-processing language designed for structured column data (like CSVs, access logs, or command output):
bash
# Print specific columns ($1 = first column, $4 = fourth column)
# Example: List usernames and default shells from /etc/passwd (delimiter -F :)
awk -F: '{print $1, $7}' /etc/passwd
# Parse Nginx access log to extract IP ($1) and HTTP Status ($9)
awk '{print $1, $9}' /var/log/nginx/access.log
# Conditional filtering: Print processes consuming > 10% CPU from ps aux
ps aux | awk '$3 > 10.0 {print $2, $3, $11}'
6. Text Manipulation Toolkit: wc, sort, uniq, cut, tr
bash
# 1. wc (Word Count): lines (-l), words (-w), bytes (-c)
wc -l /var/log/syslog
# 2. cut: Extract delimited fields
# Extract only IP addresses from /etc/hosts
cut -d' ' -f1 /etc/hosts
# 3. tr: Translate or delete characters
# Convert text to uppercase
echo "hello devops" | tr '[:lower:]' '[:upper:]'
# Delete Windows carriage returns (\r) from file
cat windows.sh | tr -d '\r' > unix.sh
# 4. sort & uniq: Count unique occurrences
# Real-world DevOps recipe: Top 5 IP addresses hitting your web server
awk '{print $1}' /var/log/nginx/access.log | sort | uniq -c | sort -nr | head -n 5
Summary
- Use
nanofor quick simple edits; mastervim(ito insert, Esc +:wqto save,:q!to abort). - Use
grep -rnEfor fast recursive keyword and regex searching across codebases. - Use
findto locate files by name, size, type, or age, and execute batch operations with-exec. - Use
sed -ifor automated in-place configuration replacements in CI/CD scripts. - Chain
awk,sort, anduniq -cinto high-speed log-analysis pipelines.
In the next lesson, you will master Linux permissions, ownership, octal modes (chmod 755/600), and superuser delegation with sudo!