bash-linux

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Translated

Bash/Linux terminal patterns. Critical commands, piping, error handling, scripting. Use when working on macOS or Linux systems.

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Translated version includes tags in frontmatter
bash-scriptinglinux-terminalcommand-line-toolsprocess-managementerror-handling

SKILL.md Content

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Bash Linux Patterns

Essential patterns for Bash on Linux/macOS.

1. Operator Syntax

Chaining Commands

OperatorMeaningExample
;
Run sequentially
cmd1; cmd2
&&
Run if previous succeeded
npm install && npm run dev
||
Run if previous failed
npm test || echo "Tests failed"
|
Pipe output
ls | grep ".js"

2. File Operations

Essential Commands

TaskCommand
List all
ls -la
Find files
find . -name "*.js" -type f
File content
cat file.txt
First N lines
head -n 20 file.txt
Last N lines
tail -n 20 file.txt
Follow log
tail -f log.txt
Search in files
grep -r "pattern" --include="*.js"
File size
du -sh *
Disk usage
df -h

3. Process Management

TaskCommand
List processes
ps aux
Find by name
ps aux | grep node
Kill by PID
kill -9 <PID>
Find port user
lsof -i :3000
Kill port
kill -9 $(lsof -t -i :3000)
Background
npm run dev &
Jobs
jobs -l
Bring to front
fg %1

4. Text Processing

Core Tools

ToolPurposeExample
grep
Search
grep -rn "TODO" src/
sed
Replace
sed -i 's/old/new/g' file.txt
awk
Extract columns
awk '{print $1}' file.txt
cut
Cut fields
cut -d',' -f1 data.csv
sort
Sort lines
sort -u file.txt
uniq
Unique lines
sort file.txt | uniq -c
wc
Count
wc -l file.txt

5. Environment Variables

TaskCommand
View all
env
or 
printenv
View one
echo $PATH
Set temporary
export VAR="value"
Set in script
VAR="value" command
Add to PATH
export PATH="$PATH:/new/path"

6. Network

TaskCommand
Download
curl -O https://example.com/file
API request
curl -X GET https://api.example.com
POST JSON
curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' URL
Check port
nc -zv localhost 3000
Network info
ifconfig
or 
ip addr

7. Script Template

bash
#!/bin/bash
set -euo pipefail  # Exit on error, undefined var, pipe fail

# Colors (optional)
RED='\033[0;31m'
GREEN='\033[0;32m'
NC='\033[0m'

# Script directory
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

# Functions
log_info() { echo -e "${GREEN}[INFO]${NC} $1"; }
log_error() { echo -e "${RED}[ERROR]${NC} $1" >&2; }

# Main
main() {
    log_info "Starting..."
    # Your logic here
    log_info "Done!"
}

main "$@"

8. Common Patterns

Check if command exists

bash
if command -v node &> /dev/null; then
    echo "Node is installed"
fi

Default variable value

bash
NAME=${1:-"default_value"}

Read file line by line

bash
while IFS= read -r line; do
    echo "$line"
done < file.txt

Loop over files

bash
for file in *.js; do
    echo "Processing $file"
done

9. Differences from PowerShell

TaskPowerShellBash
List files
Get-ChildItem
ls -la
Find files
Get-ChildItem -Recurse
find . -type f
Environment
$env:VAR
$VAR
String concat
"$a$b"
"$a$b"
(same)
Null check
if ($x)
if [ -n "$x" ]
PipelineObject-basedText-based

10. Error Handling

Set options

bash
set -e          # Exit on error
set -u          # Exit on undefined variable
set -o pipefail # Exit on pipe failure
set -x          # Debug: print commands

Trap for cleanup

bash
cleanup() {
    echo "Cleaning up..."
    rm -f /tmp/tempfile
}
trap cleanup EXIT
Remember: Bash is text-based. Use 
&&
for success chains, 
set -e
for safety, and quote your variables!