AWK is my favorite programming language for its excellent design—excellent defaults which help you solve specific problems in a fun way. The language was invented by Aho, Weinberger, and Kernighan to do text-processing and that’s great. But the real reason I love AWK is because of The AWK Programming Language technical book. I always keep a copy of either edition within arms reach as an evergreen reminder that parsimonious beauty is possible.

Learn interactively

You learn AWK by writing programs; but that’s true for all languages. AWK is fun to learn because you can learn interactively. Write your AWK program, then pass data into stdin and see what happens.

For example, consider the following interactive learning session where you loop over fields of a record. At first you solve the specific case of 2 fields and then generalize to any number of fields (with the NF builtin).

Fire up an AWK program.

awk '{ for (i = 1; i <= 2; i++)
    printf "$" i "=" $i " "
    print "[...]" }'

Type at it.
```
foo bar <enter>
foo bar baz <enter>
```
Your output should look like the following:
```
$ awk '{ for (i = 1; i <= 2; i++)
> printf "$" i "=" $i " "
> print "[...]" }'
foo bar
$1=foo $2=bar [...]
foo bar baz
$1=foo $2=bar [...]
```
Consider the following:
- Observation: Notice that this AWK program only does the right thing for 2 fields.
- Insight: Realize that you can play with the program interatively (by passing input on stdin).

Generalize (with the NF variable).

awk '{ for (i = 1; i <= NF; i++)
    printf("$%d=%s%s", i, $i, i == NF ? "\n" : " ")}'

Type at it—interactively, validate things work as you expect.
```
hello world <enter>
hello world again <enter>
```
Your output should look like the following:
```
$ awk '{ for (i = 1; i <= NF; i++)
> printf("$%d=%s%s", i, $i, i == NF ? "\n" : " ")}'
hello world
$1=hello $2=world
hello world again
$1=hello $2=world $3=again
```
Aside: Notice the expr1 ? expr2 : expr3 conditional expression which helps generalize the program by accomdating the boundary condition of printing the last field.

Conclusion

I really love AWK. The excellent design is well-described by an excellent book. To get started, try typing at an AWK program like awk '{ print $1, $2 }'.

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