在Linux下，使用
gets(cmd)
函數報錯：warning: the 'gets' function is dangerous and should not be used.
解決辦法：采用
fgets(cmd,100,stdin);//100為size
問題解決！
fgets從stdin中讀字符，直至讀到換行符或文件結束，但一次最多讀size個字符。讀出的字符連同換行符存入緩沖區cmd中。返回指向cmd的指針。
gets把從stdin中輸入的一行信息存入cmd中，然后將換行符置換成串結尾符NULL。用戶要保證緩沖區的長度大於或等於最大的行長。
gets的詳細解釋：
char * gets ( char * str );//Get string from stdin
Reads characters from stdin and stores them as a string into str until a newline character ('\n') or the End-of-File is reached.
The ending newline character ('\n') is not included in the string.
A null character ('\0') is automatically appended after the last character copied to str to signal the end of the C string.
Notice that gets does not behave exactly as fgets does with stdin as argument: First, the ending newline character is not included with gets while with fgets it is. And second, gets does not let you specify a limit on how many characters are to be read, so you must be careful with the size of the array pointed by str to avoid buffer overflows.
說明：紅色部分很好地解釋了“the 'gets' function is dangerous and should not be used”這個warning的原因。
參考鏈接：http://www.cplusplus.com/reference/clibrary/cstdio/gets/