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flags.go
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flags.go
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package main
import (
"fmt"
"os"
"strings"
flag "github.com/spf13/pflag"
)
var (
flagset = flag.NewFlagSet("selpg", flag.ContinueOnError)
flagInfo = map[string]string{
"s": "startpage",
"e": "endpage",
"l": "pagesize",
"f": "f",
"d": "destination",
}
filename = ""
)
func makeHasFlagMap() map[string]bool {
hasFlag := make(map[string]bool)
isFilename := false
for _, oneArg := range os.Args {
toContinue := false
// check whether oneArg is a flag
for short, full := range flagInfo {
if strings.HasPrefix(oneArg, "--"+full) {
hasFlag[short] = true
// next oneArg can be a filename
isFilename = true
toContinue = true
break
} else if strings.HasPrefix(oneArg, "-"+short) {
hasFlag[short] = true
// next oneArg can be a filename if oneArg != "-s"
isFilename = oneArg != short
toContinue = true
break
}
}
if toContinue {
continue
}
// oneArg is not a flag: it can be a filename
if isFilename {
filename = oneArg
} // else: oneArg is like 10 in "-s 10"
isFilename = true
}
return hasFlag
}
func processFlags() error {
flagset.SortFlags = false
// define flags
flagset.UintP(flagInfo["s"], "s", 0, "start_page, must be specified")
flagset.UintP(flagInfo["e"], "e", 0, "end_page, must be specified and no smaller than start_page")
flagset.UintP(flagInfo["l"], "l", 72, "page_size, exclusive to -f")
flagset.BoolP(flagInfo["f"], "f", false, "use \\f instead of page_size to delimit a page, exclusive to -l")
flagset.StringP(flagInfo["d"], "d", "", "printer to output to (default stdout)")
// parse flags
err := flagset.Parse(os.Args[1:])
if err != nil {
os.Exit(2)
}
// parsed results
startPagenum, _ := flagset.GetUint(flagInfo["s"])
endPagenum, _ := flagset.GetUint(flagInfo["e"])
pageSize, _ := flagset.GetUint(flagInfo["l"])
dest, _ := flagset.GetString(flagInfo["d"])
hasFlag := makeHasFlagMap()
_, hasS := hasFlag["s"]
_, hasE := hasFlag["e"]
_, hasL := hasFlag["l"]
_, hasF := hasFlag["f"]
_, hasD := hasFlag["d"]
if !hasS {
return fmt.Errorf("missing argument for -s")
}
if startPagenum == 0 {
return fmt.Errorf("invalid argument \"%v\" for -s: expected a positive integer", startPagenum)
}
if !hasE {
return fmt.Errorf("missing argument for -e")
}
if endPagenum == 0 {
return fmt.Errorf("invalid argument \"%v\" for -e: expected a positive integer", endPagenum)
}
if startPagenum > endPagenum {
return fmt.Errorf("invalid argument \"%v\" for -e: end_page (%d) must be no smaller than start_page (%d)", endPagenum, endPagenum, startPagenum)
}
if hasL && hasF {
return fmt.Errorf("-l and -f must not be specified simultaneously")
}
if hasL && pageSize == 0 {
return fmt.Errorf("invalid argument \"%v\" for -l: expected a positive integer", pageSize)
}
if hasD && len(dest) == 0 {
return fmt.Errorf("invalid argument \"%v\" for -d: should name one destination", dest)
}
return nil
}