#include<signal.h>
#include<unistd.h>
static void func(){return;}
int main(){
int n=0;
char line[256];
signal(SIGALRM,func);
alarm(10);
n=read(0,line,256);
alarm(0);
write(1,line,n);
}

$strace ./a.out
...
rt_sigaction(SIGALRM, {0x8048424, [ALRM], SA_RESTORER|SA_RESTART, 0x40046678}, {SIG_DFL}, 8) = 0
alarm(10) = 0
read(0, 0xbffff980, 256) = ? ERESTARTSYS (To be restarted)
--- SIGALRM (Alarm clock) @ 0 (0) ---
sigreturn() = ? (mask now [RTMIN])
read(0,

select使えばいいんだろうけど。