我的被​​叫脚本中有“捕获'echo ignore'USR1”的字样，为什么调用脚本被杀死？

Question

说我有以下两个bash脚本：

的/ tmp /捕手：

#!/bin/bash
trap 'echo trapper: ignoring USR1' USR1
"$(dirname $0)"/usr1er & p=$!
sleep 1
echo trapper: now killing usr1er
kill $p
echo trapper: sleeping
sleep 1
echo trapper: reached end of trapper

的/ tmp / usr1er：

#!/bin/bash
trap 'echo "usr1er: EXIT received, sending USR1"; kill -USR1 0' EXIT
while sleep 1;do echo usr1er: sleeping;done

捕获程序应该捕获USR1并直接忽略它。 它启动usr1er，并使用USR1信号终止其进程组。 现在，如果我从交互式shell本身以脚本形式启动trapper，它将杀死usr1er并正常退出：

$ /tmp/trapper; echo done
trapper: now killing usr1er
trapper: sleeping
usr1er: EXIT received, sending USR1
/tmp/trapper: line 9: 16596 Terminated              "$(dirname $0)"/usr1er
trapper: ignoring USR1
trapper: reached end of trapper
done

如果我尝试$(/tmp/trapper) ，它将退出整个外壳。 同样，如果我制作一个单独的脚本来调用/tmp/trapper ，如/tmp/outer ：

#!/bin/bash
"$(dirname $0)"/trapper
echo outer: reached end of outer

它被杀死而没有打印“外部的到达端”：

$ /tmp/outer
trapper: now killing usr1er
trapper: sleeping
usr1er: EXIT received, sending USR1
User defined signal 1
/tmp/trapper: line 9: 23544 Terminated              "$(dirname $0)"/usr1er
User defined signal 1
trapper: ignoring USR1
trapper: reached end of trapper

为什么？

Answer 1

看来， $() 不以单独的进程组/ PGID启动过程（apparantly制作Cc工作）。

同样，任何非交互式外壳程序也不会为其子级启动单独的PGID（除非您使用set -m打开作业控制）：

$ bash -c '/tmp/trapper;echo done'
trapper: now killing usr1er
trapper: sleeping
usr1er: EXIT received, sending USR1
User defined signal 1
$ /tmp/trapper: line 9: 17522 Terminated              "$(dirname $0)"/usr1er
trapper: ignoring USR1
trapper: reached end of trapper

请注意，“ done”未打印，不会捕获USR1的外部bash脚本会被杀死，而trapper会一直活到最后。

您可以通过在脚本中添加ps -o %p%r%c -p$$来检查每个进程的PGID：

$ /tmp/outer
  PID  PGID COMMAND
27630 27630 outer
  PID  PGID COMMAND
27633 27630 trapper
  PID  PGID COMMAND
27635 27630 usr1er
trapper: now killing usr1er
trapper: sleeping
usr1er: EXIT received, sending USR1
User defined signal 1
$ /tmp/trapper: line 9: 27635 Terminated              "$(dirname $0)"/usr1er
trapper: ignoring USR1
trapper: reached end of trapper

Answer 2

试试这个变化

的/ tmp / usr1er：

#!/bin/bash
trap 'echo "usr1er: EXIT received, sending USR1"; kill -USR1 $PPID' TERM
while sleep 1;do echo usr1er: sleeping;done

处理了TERM信号而不是EXIT，并将USR1发送到$PPID而不是0