分类： LINUX
2012-04-19 09:56:15
#include
#include
#include
int main()
{
pid_t pid = 0;
if((pid = fork()) < 0)
{
printf("frok erro and exit\n");
exit(0);
}
if(0==pid)
{
#ifdef SETGROUP
setpgrp();
#endif
while(1)
{
printf("In child, pid is %d, pgid is %d\n", getpid(),
getpgrp());
sleep(2);
}
}else
{
while(1)
{
printf("In parent, pid is %d, pgid is %d\n", getpid(),
getpgrp());
sleep(2);
}
}
return 0;
}
在没有定义SETGROUP时，输出如下：
./a.out
In child, pid is 24010, pgid is 24009
In parent, pid is 24009, pgid is 24009
In parent, pid is 24009, pgid is 24009
In child, pid is 24010, pgid is 24009
In parent, pid is 24009, pgid is 24009
In child, pid is 24010, pgid is 24009
In parent, pid is 24009, pgid is 24009
In child, pid is 24010, pgid is 24009
Ctrl+c之后父子进程都退出
在定义了SETGROUP时，输出如下：
./a.out
In child, pid is 24562, pgid is 24562
In parent, pid is 24561, pgid is 24561
In parent, pid is 24561, pgid is 24561
In child, pid is 24562, pgid is 24562
In parent, pid is 24561, pgid is 24561
In child, pid is 24562, pgid is 24562
In parent, pid is 24561, pgid is 24561
In child, pid is 24562, pgid is 24562
Ctrl+c之后父进程退出，子进程仍然运行
关于setpgrp()，该函数的调用者会把自己加入一个新的process group，并且process group leader就是自己，即process group ID就是自己的进程号。
这个例子可以确定的是：调用了setpgrp()后就不会收到Ctrl+c信号了，但是究竟是调用了setpgrp()后脱离了控制终端 还是 该进程成为了后台进程 导致的，我还不是很清楚。
网上有人说是：脱离了控制终端，但是两种情况下执行lsof可以看到如下输出：
lsof -p
24710
lsof: WARNING: can't stat() ext3 file system /dev/.static/dev
Output information may be incomplete.
COMMAND PID
USER
FD TYPE
DEVICE
SIZE
NODE NAME
a.out 24710
jsun
cwd
DIR
8,9 4096
10403851 /home/jsun
a.out 24710
jsun
rtd
DIR
8,1
4096
2 /
a.out 24710
jsun
txt
REG
8,9 7811
10404039 /home/jsun/a.out
a.out 24710
jsun
mem
REG 8,1
1241392 7242668
/lib/tls/i686/cmov/libc-2.3.6.so
a.out 24710
jsun
mem
REG
0,0
0 [vdso] (stat: No such file or directory)
a.out 24710
jsun
mem
REG
8,1 88164
7225346 /lib/ld-2.3.6.so
a.out 24710
jsun
0u CHR
136,2
4 /dev/pts/2
a.out 24710
jsun
1u CHR
136,2
4 /dev/pts/2
a.out 24710
jsun
2u CHR
136,2
4 /dev/pts/2
lsof -p
24711
lsof: WARNING: can't stat() ext3 file system /dev/.static/dev
Output information may be incomplete.
COMMAND PID
USER
FD TYPE
DEVICE
SIZE
NODE NAME
a.out 24711
jsun
cwd
DIR
8,9 4096
10403851 /home/jsun
a.out 24711
jsun
rtd
DIR
8,1
4096
2 /
a.out 24711
jsun
txt
REG
8,9 7811
10404039 /home/jsun/a.out
a.out 24711
jsun
mem
REG 8,1
1241392 7242668
/lib/tls/i686/cmov/libc-2.3.6.so
a.out 24711
jsun
mem
REG
0,0
0 [vdso] (stat: No such file or directory)
a.out 24711
jsun
mem
REG
8,1 88164
7225346 /lib/ld-2.3.6.so
a.out 24711
jsun
0u CHR
136,2
4 /dev/pts/2
a.out 24711
jsun
1u CHR
136,2
4 /dev/pts/2
a.out 24711
jsun
2u CHR
136,2
4 /dev/pts/2
lsof -p
24746
lsof: WARNING: can't stat() ext3 file system /dev/.static/dev
Output information may be incomplete.
COMMAND PID
USER
FD TYPE
DEVICE
SIZE
NODE NAME
a.out 24746
jsun
cwd
DIR
8,9 4096
10403851 /home/jsun
a.out 24746
jsun
rtd
DIR
8,1
4096
2 /
a.out 24746
jsun
txt
REG
8,9 7894
10404039 /home/jsun/a.out
a.out 24746
jsun
mem
REG 8,1
1241392 7242668
/lib/tls/i686/cmov/libc-2.3.6.so
a.out 24746
jsun
mem
REG
0,0
0 [vdso] (stat: No such file or directory)
a.out 24746
jsun
mem
REG
8,1 88164
7225346 /lib/ld-2.3.6.so
a.out 24746
jsun
0u CHR
136,2
4 /dev/pts/2
a.out 24746
jsun
1u CHR
136,2
4 /dev/pts/2
a.out 24746
jsun
2u CHR
136,2
4 /dev/pts/2
lsof -p
24747
lsof: WARNING: can't stat() ext3 file system /dev/.static/dev
Output information may be incomplete.
COMMAND PID
USER
FD TYPE
DEVICE
SIZE
NODE NAME
a.out 24747
jsun
cwd
DIR
8,9 4096
10403851 /home/jsun
a.out 24747
jsun
rtd
DIR
8,1
4096
2 /
a.out 24747
jsun
txt
REG
8,9 7894
10404039 /home/jsun/a.out
a.out 24747
jsun
mem
REG 8,1
1241392 7242668
/lib/tls/i686/cmov/libc-2.3.6.so
a.out 24747
jsun
mem
REG
0,0
0 [vdso] (stat: No such file or directory)
a.out 24747
jsun
mem
REG
8,1 88164
7225346 /lib/ld-2.3.6.so
a.out 24747
jsun
0u CHR
136,2
4 /dev/pts/2
a.out 24747
jsun
1u CHR
136,2
4 /dev/pts/2
a.out 24747
jsun
2u CHR
136,2
4 /dev/pts/2
可以看到，都打开了/dev/pts/2，感觉没有脱离控制终端，不知道我这想法对不？后者说打开了终端文件，但是该终端不一定是控制终端？那是否变成了后台进程呢？下面是一段英文来自man setpgrp
Each process group is a member of a session and each process is a member of the session of which its process group is a member.
Process groups are used for distribution of signals, and by terminals to arbitrate requests for their input: Processes that have the same process group as the terminal are foreground and may read, while others will block with a signal if they attempt to read. These calls are thus used by programs such as csh(1) to create process groups in implementing job control. The TIOCGPGRP and TIOCSPGRP calls described in termios(3) are used to get/set the process group of the control terminal.
If a session has a controlling terminal, CLOCAL is not set and a
hangup occurs, then the session leader is sent a SIGHUP.
If the session leader exits, the SIGHUP signal will be sent to each
process in the foreground process group of
the controlling terminal.
If the exit of the process causes a process group to become orphaned, and if any member of the newly-orphaned process group is stopped, then a SIGHUP signal followed by a SIGCONT signal will be sent to each process in the newly-orphaned process group.
这里父进程所在的组才是前端进程组，所以能够接收终端信号，子进程此时调用setpgrp()脱离了前端进程组，而不是脱离控制台
