bash.md

可以使用 bash 时

Trap the SIGALRM signal

$ trap "" 14 && /readflag 
Solve the easy challenge first (((((-623343)+(913340))+(-511878))+(791102))-(956792)) 
input your answer: -387571 
ok! here is your flag!! 
...

mkfifo trick

$ mkfifo pipe
$ cat pipe| ./readflag |(read l;read l;echo $l;echo $(($l))>pipe;cat)
input your answer: 
ok! here is your flag!! 
...