Abs returns absolute path , ignore error return "" as representing error.

ExpandWd only works for ./ prefix.

Fprintf is thread safe.

GetCommandList seperate cmd to []string.

IsNewer if filename1 newer than filename2.

LsDir returns slices containing contents of a directory if fname is a file, not a directory, return empty slice return: relative path.

LsRegexWd returns absolute path.

ReadString read all content from fname.

TarGz add all srcNames to outName as tar.gz file.

WriteToFile will clean the original content!!.

StopWatch is "auto-reset" stopwatch.