~/relaissrc$ gcc relais.c -g -o relais
relais.c: In function init:
relais.c:151: warning: incompatible implicit declaration of built-in function exit
relais.c: In function getport:
relais.c:180: warning: incompatible implicit declaration of built-in function exit
relais.c: In function usage:
relais.c:246: warning: incompatible implicit declaration of built-in function exit
relais.c: In function main:
relais.c:274: warning: incompatible implicit declaration of built-in function exit
relais.c:287: warning: incompatible implicit declaration of built-in function exit
relais.c:306: warning: incompatible implicit declaration of built-in function exit
relais.c:320: warning: incompatible implicit declaration of built-in function exit