为什么cron将我的程序输出重定向到/dev/null？

Question

我试图通过cron重新启动系统进程，并通过电子邮件发送进程的启动输出。我原以为将STDOUT和SDTERR重定向到/dev/null会“沉默”输出，但唉，这是行不通的。如何让cron安静地重新启动此服务？crontab条目：

0 6 * * * service sympa stop &>/dev/null; service sympa start &> /dev/null

重新启动电子邮件的输出示例：

 Stopping Sympa bounce manager bounced
   ...done.
 * Stopping Sympa task manager task_manager
   ...done.
 * Stopping Sympa mailing list archive manager archived
   ...done.
 * Stopping Sympa mailing list manager sympa
   ...done.
 ... waiting Prototype mismatch: sub Lock::LOCK_SH () vs none at /home/sympa/bin/Lock.pm line 38.
Constant subroutine LOCK_SH redefined at /home/sympa/bin/Lock.pm line 38.
Prototype mismatch: sub Lock::LOCK_EX () vs none at /home/sympa/bin/Lock.pm line 39.
Constant subroutine LOCK_EX redefined at /home/sympa/bin/Lock.pm line 39.
Prototype mismatch: sub Lock::LOCK_NB () vs none at /home/sympa/bin/Lock.pm line 40.
Constant subroutine LOCK_NB redefined at /home/sympa/bin/Lock.pm line 40.

Answer 1

我想你会想要用下面这句话

service sympa stop >/dev/null 2>&1。

第一个命令将stdout发送到/dev/null，然后2>&1使stderr (standard error)被发送到stdout(standard output)要去的地方，这就是/dev/null，从而导致抑制输出。