$ cat logs.txt
GET /robots.txt HTTP/1.1
HEAD /README.md HTTP/1.1
GET /wp-admin/ HTTP/1.0

$ prig 'Println("https://example.com" + S(2))' <logs.txt
https://example.com/robots.txt
https://example.com/README.md
https://example.com/wp-admin/

Prig v1.0.0 - Copyright (c) 2022 Ben Hoyt

Usage: prig [options] [-b 'begin code'] 'per-record code' [-e 'end code']

Prig is for Processing Records In Go. It's like AWK, but snobbish (Go! static
typing!). It runs 'begin code' first, then runs 'per-record code' for every
record (line) in the input, then runs 'end code'. Prig uses "go build", so it
requires the Go compiler: https://go.dev/doc/install

Options:
  -F char | re     field separator (single character or multi-char regex)
  -g executable    Go compiler to use (eg: "go1.18rc1", default "go")
  -h, --help       print help message and exit
  -i import        import Go package (normally automatic)
  -s               print formatted Go source instead of running
  -V, --version    print version number and exit

Built-in functions:
  F(i int) float64 // return field i as float64, int, or string
  I(i int) int     // (i==0 is entire record, i==1 is first field)
  S(i int) string

  NF() int // return number of fields in current record
  NR() int // return number of current record

  Print(args ...interface{})                 // fmt.Print, but buffered
  Printf(format string, args ...interface{}) // fmt.Printf, but buffered
  Println(args ...interface{})               // fmt.Println, but buffered

  Match(re, s string) bool            // report whether s contains match of re
  Replace(re, s, repl string) string  // replace all re matches in s with repl
  Submatches(re, s string) []string   // return slice of submatches of re in s
  Substr(s string, n[, m] int) string // s[n:m] but safe and allow negative n/m

  Sort[T int|float64|string](s []T) []T
    // return new sorted slice; also Sort(s, Reverse) to sort descending
  SortMap[T int|float64|string](m map[string]T) []KV[T]
    // return sorted slice of key-value pairs
    // also Sort(s[, Reverse][, ByValue]) to sort descending or by value

Examples:
  # Run an arbitrary Go snippet; don't process input
  prig -b 'Println("Hello, world!", math.Pi)'

  # Print the average value of the last field
  prig -b 's := 0.0' 's += F(NF())' -e 'Println(s / float64(NR()))'

  # Print 3rd field in milliseconds if line contains "GET" or "HEAD"
  prig 'if Match(`GET|HEAD`, S(0)) { Printf("%.0fms\n", F(3)*1000) }'

  # Print frequencies of unique words, most frequent first
  prig -b 'freqs := map[string]int{}' \
       'for i := 1; i <= NF(); i++ { freqs[strings.ToLower(S(i))]++ }' \
       -e 'for _, f := range SortMap(freqs, ByValue, Reverse) { ' \
       -e 'Println(f.K, f.V) }'