SIGTTOU 和SIGTTIN

#include "stdio.h"
#include "unistd.h"

int main(int argc, char const *argv[])
{
	char buf[10]="xxxxxxxxx";
	write(STDOUT_FILENO,buf, 5);
	return 0;
}

gcc out.c -o out

(要先执行命令  stty tostop ,禁止后台作业输出至控制终端)

./out &   或者  nohup ./out &

用strace查看

write(2, "nohup: ", 7)                  = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTOU {si_signo=SIGTTOU, si_code=SI_KERNEL, si_value={int=0, ptr=0x100000000}} ---
--- stopped by SIGTTOU ---
write(2, "nohup: ", 7)                  = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTOU {si_signo=SIGTTOU, si_code=SI_KERNEL, si_value={int=0, ptr=0x100000000}} ---
--- stopped by SIGTTOU ---
write(2, "nohup: ", 7)                  = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTOU {si_signo=SIGTTOU, si_code=SI_KERNEL, si_value={int=0, ptr=0x100000000}} ---
--- stopped by SIGTTOU ---

#include "stdio.h"
#include "unistd.h"

int main(int argc, char const *argv[])
{
	char buf[10]={0};
	read(STDIN_FILENO,buf, 5);
	write(STDOUT_FILENO,buf, 5);
	return 0;
}

gcc in.c -o in

./in &   或者  nohup ./in &

用strace查看

read(0, 0x7ffded8eae70, 5)              = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTIN {si_signo=SIGTTIN, si_code=SI_KERNEL, si_value={int=0, ptr=0x100000000}} ---
--- stopped by SIGTTIN ---
read(0, 0x7ffded8eae70, 5)              = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTIN {si_signo=SIGTTIN, si_code=SI_KERNEL, si_value={int=0, ptr=0x100000000}} ---
--- stopped by SIGTTIN ---
read(0, 0x7ffded8eae70, 5)              = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTIN {si_signo=SIGTTIN, si_code=SI_KERNEL, si_value={int=0, ptr=0x100000000}} ---
--- stopped by SIGTTIN ---

对于有标准输入输出的后台运行程序，应对其标准输入输出重定向。

(shell将作业转为前台进程组时，会将继续信号SIGCONT，送给该作业)