Idiomatic Awk

/pattern/ is the same as $0 ~ /pattern/
- i.e., expression implicitly applied to $0, which is whole line
default action is print
- so awk '/pattern/' prints every line matching the pattern
- and awk 1 prints every line
you can use awk for substitution, the 1 prints the line:
```
awk '{sub(/pattern/, "foobar")} 1'
```
exclude empty lines (where NF, number of fields, is 0):
```
awk 'NF'
```
remove last field:
```
awk 'NF--'
```
prepend line numbers (yes you can just use nl instead):
```
awk '$0 = NR" "$0'
```
deduplicate lines:
```
awk '!a[$0]++'
```
print in 5 columns:
```
awk 'ORS = NR % 5 ? FS : RS'
```
replacing delimiters: the important thing here is that $0 doesn’t get recomputed unless AWK thinks it has to be. and that happens when a field is changed.
```
awk FS=\; OFS=, '$1=$1'
```
Also, any files that have an equal sign get treated as variables. Consequently, if yoru filename has an equal sign, you’re gonna have a bad time.