Interview › Scripting (Bash, Groovy)
What is the difference between NR and NF in awk? [Advanced]
Answer
NR is the current input record number, usually the line number across all files. NF is the number of fields in the current record. NR tells where I am; NF tells how many fields the current line has.
Technical explanation
Use NR for skipping headers, printing line numbers, or selecting line ranges.
Use NF for checking column counts or accessing the last field with $NF.
When processing multiple files, FNR is the record number within the current file, while NR is cumulative.
Hands-on example
awk 'NR == 1 {print "header:", $0} NR > 1 {print NR, NF, $NF}' data.txt
# Skip CSV header and print last field.
awk -F, 'NR > 1 {print $NF}' data.csv
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