When working in the Linux shell, you can combine simple commands to perform complex tasks quickly and efficiently. In this post, we’ll explore a few powerful tools—grep, redirection (>), logical AND (&&), pipes (|), and how they work together. We’ll also touch on nano - and wc with practical examples.
Let’s break it all down.
1. grep: Find What You’re Looking For
grep is used to search for text patterns inside files or output. You can think of it as a text filter.
Basic Usage:
grep "hello" file.txt
This command searches for the word “hello” in file.txt.
Useful Flags:
-i: Case-insensitive search-r: Recursive search through directories-n: Show line numbers--color=auto: Highlights matches
Example:
cat notes.txt | grep -i "error"
This prints all lines from notes.txt containing “error”, regardless of case.
2. Redirection (Output Insertion) ( > )
The > operator redirects output from a command into a file. If the file doesn’t exist, it’s created. If it does, it gets overwritten.
Example:
echo "This is a test" > test.txt
This writes “This is a test” into test.txt, replacing its contents if the file already exists.
If you want to append instead of overwrite, use >>:
echo "Another line" >> test.txt
3. Run Only If Previous Succeeds ( && )
The && operator runs the second command only if the first command is successful (i.e., it returns an exit status of 0).
Example:
mkdir new_folder && cd new_folder
This will only try to enter new_folder if it was successfully created.
4. Piping — Chain Commands ( | )
The pipe | takes the output of one command and feeds it into another as input. This is where the real power of the shell comes in.
Example:
ls -l | grep ".txt"
This lists only the .txt files from the ls -l output.
Another:
cat bigfile.txt | grep "error" | wc -l
This counts how many lines contain the word “error” in bigfile.txt.
5. Edit from Standard Input ( nano - )
Normally, nano is used to open files, but when you use a dash -, it reads from standard input. Combine it with echo or pipes to edit output directly.
Example:
echo "Hello everyone, what is up" | nano -
This opens nano with the echoed string in a new, unnamed buffer.
You can save it manually from there if needed.
6. Count Words, Lines, and Bytes ( wc)
wc stands for “word count”, but it can also count lines and characters.
Common Usage:
wc file.txt
This gives line, word, and byte count of the file.
Count only lines:
wc -l file.txt
Combine with grep:
grep -i "warning" log.txt | wc -l
This counts how many lines contain “warning” in log.txt.
Tying It All Together
Let’s say you want to search for the word “failed” in all .log files, count how many times it appears, and then save it to a file:
grep -i "failed" *.log | wc -l > failure_count.txt
Or you want to run a command only if the previous one completes:
cp backup.db /mnt/drive && echo "Backup copied successfully"
And to edit something quickly without saving a temporary file first:
echo "Quick note" | nano -
Final Thoughts
Once you start combining these commands—grep, >, &&, |, and tools like nano and wc—you’ll be able to manipulate and process text like a pro right from the command line. These techniques are foundational and widely used in scripting, log analysis, automation, and more.
Master them now, and your shell workflow will get a serious boost.
