bt test $ bash b -1
suid.c: In function 'main':
suid.c:3: warning: incompatible implicit declaration of built-in function 'execl'
sh-3.1$ exit -----------> 又失败了
exit
bt test $ bash b -1
suid.c: In function 'main':
suid.c:3: warning: incompatible implicit declaration of built-in function 'execl'
sh-3.1# ---------------> 成功