awk — File Diffs & Set Operations

Lines in file1 not in file2 (subtract)

awk 'NR==FNR {a[$0]; next} !($0 in a)' file2 file1

Lines common to both files (intersection)

awk 'NR==FNR {a[$0]; next} $0 in a' file2 file1

Symmetric difference — lines in either but not both

awk 'NR==FNR {a[$0]=1; next} {if($0 in a) a[$0]=0; else print} END{for(k in a) if(a[k]) print k}' file1 file2

Compare expected vs actual host lists — find extras

awk 'NR==FNR {expected[$0]; next} !($0 in expected) {print "EXTRA:", $0}' expected_hosts.txt actual_hosts.txt

Compare expected vs actual host lists — find missing

awk 'NR==FNR {actual[$0]; next} !($0 in actual) {print "MISSING:", $0}' actual_hosts.txt expected_hosts.txt

Interleave lines from two files

awk 'NR==FNR {a[FNR]=$0; max=FNR; next} {print a[FNR]; print}' file1 file2