The logs I am processing is log (log4j). It is in format like:

我正在处理的日志是日志（log4j）。 格式如下：

2014-09-20 21:55:11,855 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Updated user map size: 362014-09-20 21:55:11,863 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Updated group map size: 552014-09-20 22:10:11,907 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Update now2014-09-20 22:10:11,907 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Not doing static UID/GID mapping because '/etc/nfs.map' does not exist.

Now, I want to get all the logs with a specific time range, e.g. last 4 hours. How to achieve this?

现在，我想获取具有特定时间范围（例如最近4个小时）的所有日志。 如何实现呢？

It should be with command line since it is in an automatic routine which is invoked by crond every 4 hours.

应该使用命令行因为它处于crond每4小时调用一次的自动例程中。

You can use date to generate filtering rules to filter out the logs in a specific range:

您可以使用日期来生成过滤规则，以过滤出特定范围内的日志：

# grep out latest logecho "" >$tmplogfor ((i=4; i>=1; i--)); do    grep "^$(date -d -${i}hour +'%Y-%m-%d %H')" $log >> $tmplogdone

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