Add program

README.md

@@ -1,2 +1,10 @@
-# fp
+# FP
+
 A filepath utility
+
+```
+$ fp
+usage: fp [file or directory]
+Flags:
+  -v print the file hash in (md5, sha1, sha256)
+```

go.mod

@@ -0,0 +1,3 @@
+module github.com/lotusirous/fp
+
+go 1.17

goreleaser.yml

@@ -0,0 +1,12 @@
+env:
+  - GO111MODULE=on
+before:
+  hooks:
+    - go mod download
+    - go mod tidy
+builds:
+- env:
+    - CGO_ENABLED=0
+  goos: [darwin, linux]
+  goarch: [386, arm, amd64, arm64]
+  mod_timestamp: '{{ .CommitTimestamp }}'

main.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"flag"
+	"fmt"
+	"hash"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// Digest hashes a file for a given path
+func Digest(h hash.Hash, loc string) (string, error) {
+	file, err := os.Open(loc)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+
+	buf := make([]byte, 1024)
+	if _, err := io.CopyBuffer(h, file, buf); err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(h.Sum(nil)), nil
+}
+
+// ReadFileInfo gets the abs path and follows the link
+func ReadFileInfo(path string) (string, os.FileInfo, error) {
+	abs, err := filepath.Abs(path)
+	if err != nil {
+		return "", nil, err
+	}
+	linkAbs, err := filepath.EvalSymlinks(abs)
+	if err != nil {
+		return "", nil, err
+	}
+	fi, err := os.Stat(linkAbs)
+	if errors.Is(err, os.ErrNotExist) {
+		return "", nil, err
+	} else if err != nil {
+		return "", nil, err
+	}
+
+	return linkAbs, fi, nil
+}
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: fp [file or directory]\n")
+	fmt.Fprintf(os.Stderr, "Flags:\n")
+	flag.PrintDefaults()
+	os.Exit(2)
+}
+
+func exit(w io.Writer, a ...interface{}) {
+	fmt.Fprintln(w, a...)
+	os.Exit(1)
+}
+
+var (
+	verbose = flag.Bool("v", false, `print the file hash in (md5, sha1, sha256)`)
+)
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	if flag.NArg() == 0 {
+		flag.Usage()
+	}
+
+	fd := os.Stdout // default writer
+	path := flag.Arg(0)
+
+	abs, fi, err := ReadFileInfo(path)
+	if err != nil {
+		exit(fd, "Cannot resolve the path: ", err)
+	}
+
+	fmt.Fprintf(fd, "PATH: %s\n", abs)
+	if fi.IsDir() {
+		os.Exit(0)
+	}
+
+	if *verbose {
+		hashes := map[string]hash.Hash{
+			"MD5":    md5.New(),
+			"SHA1":   sha1.New(),
+			"SHA256": sha256.New(),
+		}
+		for name, hf := range hashes {
+			if v, err := Digest(hf, abs); err != nil {
+				fmt.Fprintf(fd, "Cannot digest %s: %v", name, err)
+				os.Exit(1)
+			} else {
+				fmt.Fprintf(fd, "%s: %s\n", name, v)
+			}
+		}
+	}
+
+}