For each character in the first string, any letter that appears in the second string is replaced by the corresponding letter from the third-string.
对于第一个字符串中的每个字符,第二个字符串中的任意一个字符都由第三个字符串中相应的字母所替代。
2
The short form string should include each valid option letter, followed by a colon (:) to indicate that the command line option should be followed by a value.