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printchars.go
47 lines (42 loc) · 760 Bytes
/
printchars.go
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package main
import (
"flag"
"fmt"
"log"
"os"
"strconv"
)
func main() {
log.SetFlags(0)
log.SetPrefix("printchar: ")
flag.Usage = usage
flag.Parse()
if flag.NArg() != 2 {
printChars(32, 127)
} else {
printChars(atoi(flag.Arg(0)), atoi(flag.Arg(1)))
}
}
func printChars(start, end int64) {
if end < start {
start, end = end, start
}
for ; start <= end; start++ {
fmt.Printf("%c", start)
}
}
func atoi(str string) int64 {
n, err := strconv.ParseInt(str, 0, 64)
if err != nil {
log.Fatal(err)
}
if n < 0 || n > 0x7fffffff {
log.Fatalf("invalid range value %d", n)
}
return n
}
func usage() {
fmt.Fprintln(os.Stderr, "usage: <start> <end>")
flag.PrintDefaults()
os.Exit(2)
}