add other utils

utils/file.go

@@ -1,11 +1,79 @@
 package utils
 
 import (
+	"bufio"
+	"errors"
+	"io"
 	"os"
 	"path/filepath"
+	"regexp"
 )
 
 func SelfPath() string {
 	path, _ := filepath.Abs(os.Args[0])
 	return path
 }
+
+func SelfDir() string {
+	return filepath.Dir(SelfPath())
+}
+
+// FileExists reports whether the named file or directory exists.
+func FileExists(name string) bool {
+	if _, err := os.Stat(name); err != nil {
+		if os.IsNotExist(err) {
+			return false
+		}
+	}
+	return true
+}
+
+// search a file in paths.
+// this is offen used in search config file in /etc ~/
+func LookFile(filename string, paths ...string) (fullpath string, err error) {
+	for _, path := range paths {
+		if fullpath = filepath.Join(path, filename); FileExists(fullpath) {
+			return
+		}
+	}
+	err = errors.New(fullpath + " not found in paths")
+	return
+}
+
+// like command grep -E
+// for example: GrepE(`^hello`, "hello.txt")
+// \n is striped while read
+func GrepE(patten string, filename string) (lines []string, err error) {
+	re, err := regexp.Compile(patten)
+	if err != nil {
+		return
+	}
+
+	fd, err := os.Open(filename)
+	if err != nil {
+		return
+	}
+	lines = make([]string, 0)
+	reader := bufio.NewReader(fd)
+	prefix := ""
+	for {
+		byteLine, isPrefix, er := reader.ReadLine()
+		if er != nil && er != io.EOF {
+			return nil, er
+		}
+		line := string(byteLine)
+		if isPrefix {
+			prefix += line
+			continue
+		}
+
+		line = prefix + line
+		if re.MatchString(line) {
+			lines = append(lines, line)
+		}
+		if er == io.EOF {
+			break
+		}
+	}
+	return lines, nil
+}