Converts a string into an int16.

Converts a string into an int64.

Fatal when having an error.

Copies a file from src to dest with file permission 0666.

Check whether a critical directory exists.

Check whether a critical file exists.

Check whether a directory exists.

Check whether a file exists.

Converts an int16 into a string.

Converts an int64 into a string.

Returns true when the string is a number.

Now returns the time of now in the format "YYYY-MM-DD HH:MM:SS".

today returns the date of today in the format "YYYY-MM-DD".