Nash supports the full suite of Unix pipe and redirection operators, allowing you to build powerful command pipelines.
Simple Pipes Pipes (|) connect the output of one command to the input of another.
Basic pipe
Filter output with grep: user@nash:/home/user$ cat welcome.txt | grep Nash Welcome to Nash!
Count lines
user@nash:/home/user$ ls | wc -l 5
Search environment variables
user@nash:/home/user$ env | grep USER USER = user LOGNAME = user
Chained Pipes You can chain multiple commands together for complex data processing.
Example: Text Processing Pipeline user@nash:/home/user$ echo "apple\nbanana\napple\ncherry\nbanana\napple" > fruits.txt user@nash:/home/user$ cat fruits.txt apple banana apple cherry banana apple user@nash:/home/user$ cat fruits.txt | sort | uniq -c 3 apple 2 banana 1 cherry
The pipeline sort | uniq is a common pattern: sort groups identical lines together, then uniq removes duplicates.
Example: Log Analysis user@nash:/home/user$ cat > access.log 192.168.1.1 GET /api/users 192.168.1.2 POST /api/login 192.168.1.1 GET /api/posts 192.168.1.3 GET /api/users 192.168.1.1 DELETE /api/posts/5 user@nash:/home/user$ cat access.log | grep GET | wc -l 3 user@nash:/home/user$ cat access.log | grep "192.168.1.1" | wc -l 3 user@nash:/home/user$ cat access.log | cut -d ' ' -f1 | sort | uniq -c 3 192.168.1.1 1 192.168.1.2 1 192.168.1.3
Example: Finding and Filtering user@nash:/home/user$ mkdir -p projects/{frontend,backend,docs} user@nash:/home/user$ touch projects/frontend/app.js user@nash:/home/user$ touch projects/frontend/styles.css user@nash:/home/user$ touch projects/backend/server.js user@nash:/home/user$ touch projects/docs/README.md user@nash:/home/user$ find projects -type f | grep "\.js$" projects/frontend/app.js projects/backend/server.js user@nash:/home/user$ find projects -type f | grep -v "README" | wc -l 3
Output Redirection Write to File (>) The > operator redirects output to a file, overwriting existing content:
user@nash:/home/user$ echo "First line" > output.txt user@nash:/home/user$ cat output.txt First line user@nash:/home/user$ echo "Replaced content" > output.txt user@nash:/home/user$ cat output.txt Replaced content
Append to File (>>) The >> operator redirects output to a file, appending to existing content:
user@nash:/home/user$ echo "Line 1" > log.txt user@nash:/home/user$ echo "Line 2" >> log.txt user@nash:/home/user$ echo "Line 3" >> log.txt user@nash:/home/user$ cat log.txt Line 1 Line 2 Line 3
Building Files Incrementally Create config file
Collect data
user@nash:/home/user$ echo "# Application Config" > config.txt user@nash:/home/user$ echo "PORT=8080" >> config.txt user@nash:/home/user$ echo "HOST=localhost" >> config.txt user@nash:/home/user$ echo "DEBUG=true" >> config.txt user@nash:/home/user$ cat config.txt # Application Config PORT = 8080 HOST = localhost DEBUG = true
The < operator reads input from a file:
user@nash:/home/user$ echo "line1\nline2\nline3" > input.txt user@nash:/home/user$ cat < input.txt line1 line2 line3 user@nash:/home/user$ grep "line2" < input.txt line2
Complex Pipeline Examples Example 1: Word Frequency Analysis user@nash:/home/user$ cat > story.txt the cat sat on the mat the dog sat on the log the cat and the dog user@nash:/home/user$ cat story.txt | sed 's/ /\n/g' | sort | uniq -c | sort -r 5 the 2 sat 2 on 2 cat 2 dog 1 mat 1 log 1 and
Read the file
cat story.txt reads the content
Split into words
sed 's/ /\n/g' replaces spaces with newlines (one word per line)
Sort alphabetically
sort groups identical words together
Count occurrences
uniq -c counts each unique word
Sort by frequency
sort -r sorts in reverse (highest count first)
Example 2: File Statistics user@nash:/home/user$ find /home/user -type f | wc -l > stats.txt user@nash:/home/user$ echo "---" >> stats.txt user@nash:/home/user$ find /home/user -type d | wc -l >> stats.txt user@nash:/home/user$ cat stats.txt 8 --- 5
user@nash:/home/user$ cat > users.csv name,email,role alice,[email protected] ,admin bob,[email protected] ,user charlie,[email protected] ,user user@nash:/home/user$ cat users.csv | grep -v "^name" | cut -d ',' -f2 [email protected] [email protected] [email protected] user@nash:/home/user$ cat users.csv | grep "admin" | cut -d ',' -f1,2 alice,[email protected]
Example 4: Filtered File List user@nash:/home/user$ mkdir -p src/{js,css,images} user@nash:/home/user$ touch src/js/app.js src/js/utils.js user@nash:/home/user$ touch src/css/main.css src/css/theme.css user@nash:/home/user$ touch src/images/logo.png user@nash:/home/user$ find src -type f | sort src/css/main.css src/css/theme.css src/images/logo.png src/js/app.js src/js/utils.js user@nash:/home/user$ find src -name "*.js" | sort > js_files.txt user@nash:/home/user$ find src -name "*.css" | sort >> css_files.txt user@nash:/home/user$ cat js_files.txt src/js/app.js src/js/utils.js
Combining Pipes and Redirections You can mix pipes and redirections in sophisticated ways:
user@nash:/home/user$ cat data.txt | grep "error" | sort | uniq > errors.txt user@nash:/home/user$ cat access.log | grep "GET" | cut -d ' ' -f3 | sort | uniq -c > popular_endpoints.txt user@nash:/home/user$ find . -name "*.txt" | grep -v "test" | sort >> file_inventory.txt
Real-World Session user@nash:/home/user$ mkdir analysis && cd analysis user@nash:/home/user/analysis$ cat > sales.csv date,product,amount 2024-01-01,laptop,1200 2024-01-02,mouse,25 2024-01-02,laptop,1200 2024-01-03,keyboard,80 2024-01-03,mouse,25 user@nash:/home/user/analysis$ cat sales.csv | grep -v "^date" 2024-01-01,laptop,1200 2024-01-02,mouse,25 2024-01-02,laptop,1200 2024-01-03,keyboard,80 2024-01-03,mouse,25 user@nash:/home/user/analysis$ cat sales.csv | grep -v "^date" | cut -d ',' -f2 | sort | uniq keyboard laptop mouse user@nash:/home/user/analysis$ cat sales.csv | grep -v "^date" | cut -d ',' -f2 | sort | uniq -c | sort -r 2 mouse 2 laptop 1 keyboard user@nash:/home/user/analysis$ cat sales.csv | grep "laptop" | wc -l 2 user@nash:/home/user/analysis$ cat sales.csv | grep "laptop" > laptop_sales.txt user@nash:/home/user/analysis$ cat laptop_sales.txt 2024-01-01,laptop,1200 2024-01-02,laptop,1200
Redirection Operators Operator Description Behavior |Pipe Connects stdout of left command to stdin of right >Output redirect Writes stdout to file (overwrites) >>Append redirect Appends stdout to file <Input redirect Reads file content as stdin
Remember: > replaces, >> appends. Use > when starting fresh, >> when accumulating data.
