Working with CSV data

Create a CSV table and filter rows with Linux tools (grep, awk, sort). The validator reads the result file.

Duration: 25 minLevel: BeginnerExercises: 5

Create and filter a table

Analysing CSV data

CSV ("Comma-Separated Values") is the simplest table format: plain text, columns separated by commas, one line per record. Excel, databases and APIs exchange data this way. You analyse CSV with the Linux tools grep, wc, cut and sort.

Key terms & tools

Header: the first line with the column names.
grep: filters lines containing a pattern.
wc -l: counts lines.
cut -d, -f1: cuts out the 1st column (delimiter ,).
sort: sorts lines alphabetically.

Work in the folder /home/student/csv/ (mkdir -p /home/student/csv).

Your goal

You create a CSV table and analyse it: filter, count, extract columns, sort.

Exercises

1. Create a CSV
Concept: CSV structure. First line = column names, then one line per record. Create a table schueler.csv with the header name,klasse,alter and at least four data lines.
```
mkdir -p /home/student/csv
printf "name,klasse,alter\nMax,7a,13\nLisa,7b,12\nTom,7a,13\nAnna,8a,14\n" > /home/student/csv/schueler.csv
```
Check: schueler.csv starts with name,klasse,alter and has at least 4 data lines with 3 columns each.
2. Filter for class 7a
Concept: filtering lines with grep. Extract all students of class 7a and write them to klasse-7a.csv.
```
grep ",7a," /home/student/csv/schueler.csv > /home/student/csv/klasse-7a.csv
```
The pattern ,7a, matches the class column exactly (between two commas).

Check: klasse-7a.csv contains lines with ,7a,.
3. Total number of students
Concept: counting lines. Count the data lines (excluding the header) and write only the number to anzahl.txt. tail -n +2 skips the first line.
```
tail -n +2 /home/student/csv/schueler.csv | wc -l > /home/student/csv/anzahl.txt
```
Check: anzahl.txt contains exactly one number — the count of your data lines (at least 4).
4. Extract names only
Concept: extracting a column with cut. cut -d, -f1 cuts out the 1st column (comma delimiter). Get only the names (without header) into namen.txt.
```
tail -n +2 /home/student/csv/schueler.csv | cut -d, -f1 > /home/student/csv/namen.txt
```
Check: namen.txt contains at least four lines, each with one name.
5. Sort students alphabetically
Concept: sorting while keeping the header. Sort the students alphabetically by name, but keep the header on top. Trick: output the header separately, sort the rest.
```
( head -1 /home/student/csv/schueler.csv; tail -n +2 /home/student/csv/schueler.csv | sort ) > /home/student/csv/sortiert.csv
```
Check: sortiert.csv starts with the header name,klasse,alter, followed by at least four data lines — sorted alphabetically by name.

Knowledge check: Working with CSV data

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Create and filter a table

Analysing CSV data

Key terms & tools

Your goal

Exercises

1. Create a CSV

2. Filter for class 7a

3. Total number of students

4. Extract names only

5. Sort students alphabetically

Knowledge check: Working with CSV data

Related courses

Now practice it yourself