What other `awk` variables are useful?

That's a great question! Besides NR, awk has several other built-in variables that make text processing much easier. Here are the most useful ones:

1. NF (Number of Fields)

NF represents the number of fields (columns) in the current line.

• Use case: Finding lines that don't have the expected number of columns.
• Example: awk '{print "Line " NR " has " NF " columns"}' awk_test.txt

2. FS (Field Separator)

By default, awk splits lines by spaces or tabs. FS lets you change that.

• Use case: Processing CSV files (where discovery is separated by commas).
• Example: awk 'BEGIN {FS=","} {print $1}' data.csv
• Note: You can also use the -F flag on the command line: awk -F',' '{print $1}' data.csv

3. OFS (Output Field Separator)

This defines how fields are separated when you print them using a comma.

• Use case: Converting a space-separated file to a dash-separated one.
• Example: awk 'BEGIN {OFS="-"} {print $1, $2}' awk_test.txt

4. FILENAME

This variable stores the name of the file currently being processed.

• Use case: When processing multiple files at once, it helps you identify where the data came from.
• Example: awk '{print FILENAME, $0}' *.txt

5. RS (Record Separator)

By default, a "record" is a single line (separated by a newline \n). RS allows you to define a different record separator.

• Use case: Processing data where records are separated by blank lines instead of single newlines.

Summary Table

You can try using NF on your awk_test.txt file now to see how many columns each line has