Processing CSV files in Bash Scripting - Step-by-Step Execution

Concept Flow - Processing CSV files

Start

↓

Open CSV file

↓

Read line by line

↓

Split line by commas

↓

Process fields

↓

Output or store result

↓

Repeat until end of file

↓

Close file

↓

End

This flow shows how a bash script reads a CSV file line by line, splits each line into fields by commas, processes those fields, and outputs or stores the results until the file ends.

Execution Sample

Bash Scripting

while IFS=',' read -r name age city; do
  echo "Name: $name, Age: $age, City: $city"
done < people.csv

Reads a CSV file named people.csv line by line, splits each line into name, age, and city, then prints them.

Execution Table

Step	Line Read	Variables Assigned	Action	Output
1	Alice,30,New York	name=Alice, age=30, city=New York	Print formatted info	Name: Alice, Age: 30, City: New York
2	Bob,25,Los Angeles	name=Bob, age=25, city=Los Angeles	Print formatted info	Name: Bob, Age: 25, City: Los Angeles
3	Charlie,35,Chicago	name=Charlie, age=35, city=Chicago	Print formatted info	Name: Charlie, Age: 35, City: Chicago
4			End of file reached

💡 No more lines to read; loop ends

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
name		Alice	Bob	Charlie
age		30	25	35
city		New York	Los Angeles	Chicago

Key Moments - 3 Insights

Why do we use IFS=',' before read?

IFS=',' tells the shell to split each line by commas, so each field goes into the right variable. Without it, the whole line would go into the first variable (see execution_table rows 1-3).

What happens if the CSV line has more or fewer fields?

If there are fewer fields, some variables stay empty. If more, extra fields go into the last variable. This can cause wrong assignments, so the script expects exactly three fields per line (see variable_tracker).

Why do we redirect the file into the loop with done < people.csv?

This feeds the file line by line into the loop. Without it, the loop would wait for keyboard input instead of reading the file (see concept_flow step 'Read line by line').

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'city' at step 2?

A Chicago

B New York

C Los Angeles

D Empty

💡 Hint

Check the 'Variables Assigned' column at step 2 in the execution_table.

At which step does the loop stop reading lines from the file?

A Step 4

B Step 3

C Step 2

D Step 1

💡 Hint

Look for the row where 'End of file reached' is noted in the Action column.

If the CSV file had a line 'Diana,40', what would happen to the 'city' variable at that step?

A It would contain 'Diana'

B It would be empty

C It would contain '40'

D The script would crash

💡 Hint

Refer to key_moments about fewer fields and variable assignments.

Concept Snapshot

Processing CSV files in bash:
Use 'while IFS=',' read -r var1 var2 ...; do ... done < file.csv'
IFS=',' splits lines by commas into variables
Process each line inside the loop
Loop ends when file has no more lines

Full Transcript

This example shows how to process CSV files using bash scripting. The script reads the CSV file line by line, splitting each line by commas into variables using IFS=','. Each variable holds one field from the CSV line. The script then processes or prints these variables. The loop continues until all lines are read. Key points include setting IFS to comma for correct splitting, redirecting the file into the loop, and handling lines with the expected number of fields.