Initial commit

README.md

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+# chmodulator
+
+A command-line script for deciphering linux permisions
+
+## Installation
+Download relevant executable from [here](https://github.com/sfodje/chmodulator/releases)
+
+## Usage
+```bash
+$ chmodulator 0655
+-rw-r-xr-x
+0655
+Owner: rw
+Group: rx
+Other: rx
+```
+
+```bash
+$ chmodulator -rwxr--r--
+-rwxr--r--
+0744
+Owner: rwx
+Group: r
+Other: r
+```
+
+```bash
+$ chmodulator -owner=rwx -group=r-- -other=r--
+-rwxr--r--
+0744
+Owner: rwx
+Group: r
+Other: r
+```

main.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var argument, owner, group, other string
+var permissionsKey = map[string]int{"r": 4, "w": 2, "x": 1, "-": 0}
+
+func init() {
+	if len(os.Args) == 2 && !strings.Contains(os.Args[1], "=") {
+		argument = os.Args[1]
+		os.Args = append([]string{os.Args[0]}, os.Args[2:]...)
+	}
+	// Usage overrides flag.Usage()
+	flag.Usage = func() {
+		fmt.Printf("Usage of %s:\n%s [permission e.g. -rwxrwxr-x or 775]\nor\n%s <flags>\n",
+			os.Args[0], os.Args[0], os.Args[0])
+		flag.PrintDefaults()
+	}
+	flag.StringVar(&owner, "owner", "---", "owner level permissions")
+	flag.StringVar(&group, "group", "---", "group level permissions")
+	flag.StringVar(&other, "other", "---", "other level permissions")
+}
+
+func main() {
+	flag.Parse()
+	if argument == "" && owner == "---" && group == "---" && other == "---" {
+		flag.Usage()
+		return
+	}
+	var permStr = "-" + owner + group + other
+	if argument != "" {
+		permStr = argument
+	}
+
+	if matched, _ := regexp.MatchString("^\\d+$", permStr); matched {
+		output, err := convertUIntStr(permStr)
+		checkError(err, "")
+		fmt.Println(output)
+		return
+	}
+
+	if matched, _ := regexp.MatchString("^[-rwx]+$", permStr); matched {
+		output, err := convertRWXStr(permStr)
+		checkError(err, "")
+		fmt.Println(output)
+		return
+	}
+
+	fmt.Println("Invalid argument!")
+	flag.Usage()
+}
+
+func checkError(err error, msg string) {
+	if err != nil {
+		log.Fatal(err, msg)
+	}
+	return
+}
+
+func reduce(arr []string) string {
+	var output string
+
+	for _, v := range arr {
+		output += strings.Replace(v, "-", "", -1)
+	}
+	return output
+}
+
+func convertRWXStr(str string) (string, error) {
+	var permArray = strings.Split(str, "")
+	if len(permArray) < 9 {
+		return "", fmt.Errorf("Invalid argument")
+	}
+	if len(permArray) > 9 {
+		permArray = permArray[1:]
+	}
+	str = "-" + strings.Join(permArray[:9], "")
+
+	var value int
+	var output string
+	for i, v := range permArray {
+		value += permissionsKey[v]
+		if (i+1)%3 == 0 {
+			output += fmt.Sprintf("%d", value)
+			value = 0
+		}
+	}
+
+	var ownerPerms = permArray[0:3]
+	var groupPerms = permArray[3:6]
+	var otherPerms = permArray[6:9]
+
+	return fmt.Sprintf("%s\n%s\nOwner: %s\nGroup: %s\nOther: %s\n",
+		str, "0"+output, reduce(ownerPerms), reduce(groupPerms), reduce(otherPerms)), nil
+
+}
+
+func convertUIntStr(str string) (string, error) {
+	var permArray = strings.Split(str, "")
+	if len(permArray) < 3 {
+		return "", fmt.Errorf("Invalid argument")
+	}
+	if len(permArray) > 3 {
+		permArray = permArray[1:]
+	}
+	str = "0" + strings.Join(permArray[:3], "")
+	var output = []string{"-"}
+	for _, v := range permArray {
+		i, err := strconv.Atoi(v)
+		if err != nil {
+			return "", err
+		}
+		if i -= permissionsKey["r"]; i >= 0 {
+			output = append(output, "r")
+		} else {
+			i += permissionsKey["r"]
+			output = append(output, "-")
+		}
+
+		if i -= permissionsKey["w"]; i >= 0 {
+			output = append(output, "w")
+		} else {
+			i += permissionsKey["w"]
+			output = append(output, "-")
+		}
+
+		if i -= permissionsKey["x"]; i >= 0 {
+			output = append(output, "x")
+		} else {
+			i += permissionsKey["x"]
+			output = append(output, "-")
+		}
+	}
+
+	var ownerPerms = output[1:][0:3]
+	var groupPerms = output[1:][3:6]
+	var otherPerms = output[1:][6:9]
+
+	return fmt.Sprintf("%s\n%s\nOwner: %s\nGroup: %s\nOther: %s\n",
+		strings.Join(output, ""), str, reduce(ownerPerms), reduce(groupPerms), reduce(otherPerms)), nil
+}