Linux 从 tail -f 输出管道到 grep 后写入文件
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write to a file after piping output from tail -f through to grep
提问by Reddy
I'm looking to write to a file after piping output from tail -f through to grep. Say,write to a file "temp" for all lines with "Playing:" within in error_log "FreeSwitch.log".
我希望在将 tail -f 的输出通过管道传输到 grep 后写入文件。比如说，将 error_log “FreeSwitch.log”中带有“Playing:”的所有行写入文件“temp”。
tail -f "/var/lof/freeswitch/freeswitch.log" | grep "Playing:" > temp
but not working ! It is a centos 5.5
但不工作！这是一个centos 5.5
回答by John Kugelman
Did you put the file name after the >?
你把文件名放在了之后>吗？
tail -f /var/lof/freeswitch/freeswitch.log | grep "Playing:" > temp
回答by Sergey
-f, --follow[={name|descriptor}]
output appended data as the file grows;
It scans the file as it grows. And it is a process with an interval. You can only interrupt it.
它随着文件的增长而扫描文件。这是一个有间隔的过程。你只能打断它。
Use parameter:
使用参数：
-c, --bytes=K
output the last K bytes; alternatively, use -c +K to output bytes starting with the Kth of each file
or
或者
-n, --lines=K
output the last K lines, instead of the last 10; or use -n +K to output lines starting with the Kth
EDIT: as bmk said:
编辑：正如 bmk 所说：
grep --line-buffered
think it will help you
认为它会帮助你
回答by bmk
Maybe you have an issue with buffering? See BashFAQ: What is buffering?
也许你有缓冲问题？请参阅BashFAQ：什么是缓冲？
You could e.g. try:
你可以尝试：
tail -f /var/lof/freeswitch/freeswitch.log | grep --line-buffered "Playing:" > temp
回答by BX16Soupapes
thanks for your help.
谢谢你的帮助。
here is my code to insert into mysql with the word "error":
这是我用“错误”一词插入 mysql 的代码：
tail -f /var/log/httpd/error_log | \
grep -E --line-buffered "error" | \
while read line; do \
#echo -e "MY LINE: ${line}"; done
echo "INSERT INTO logs (logid,date,log) VALUES (NULL, NOW(), '${line}');" | mysql -uUSERDB -pPASSDB DBNAME; done
