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将终端命令过滤到文本文件

tag-icon • tag-icon command-line grep
将终端命令过滤到文本文件

问题：我有dmesg | grep ttyUSB 一个具有以下输出的命令：

[    7.648896] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB0
[    7.649091] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB1
[    7.649502] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB2
[17406.327030] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[17406.329670] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[17406.334036] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[90128.405694] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB0
[90128.405987] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB1
[90128.406295] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB2
[90132.905458] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB3
[90132.905791] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB4
[90132.906541] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB5
[90148.661532] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB6
[90148.661828] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB7
[90148.662440] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB8

需要将此输出重定向到文本文件，为此我使用以下命令：

dmesg | grep ttyUSB > test.txt

一切正常，但我只需要列出可用的端口。我希望文本文件输出如下：

ttyUSB0 
ttyUSB1 
ttyUSB2 
ttyUSB3

我怎样才能做到这一点？

答案1

只需使用此命令：

dmesg | egrep -o "ttyUSB[0-9]+" | sort -u > test.txt

它将匹配并返回 ttyUSB 模式。

从man grep：

   -o, --only-matching
          Print only the matched (non-empty) parts of a matching line,
          with each such part on a separate output line.

答案2

我认为这个问题比宣传的要难一些。仅仅解析dmesg实例ttyUSB*并不能让你知道它当前是否可用。它可能刚刚被断开了。

下面通过查看当前的状态。它通过查找to ...和实例来实现这一点，并且只使用位于行尾的from ...那些实例。to ttyUSB*

dmesg | tac | awk '$NF~/ttyUSB[0-9]+/ && !a[$NF]++ && $(NF-1)=="to" {print $NF}'

快速解释一下：

  • tac反转输入，所以我们先处理最近的
  • $NF ~ /ttyUSB[0-9]+/是一个正则表达式，检查最后一个字段是否是ttyUSB*
  • !a[$NF]++检查我们之前是否见过此字段
  • $(NF-1) == "to"对倒数第二个字段进行过滤，以确保我们处理的是行to ...。

为了测试这一点，我简单地获取了您的输出并删除了第二个连接。在我的示例中，ttyUSB2 已连接，然后断开连接，并且从未重新连接。它不应该可用。

$ cat testdmesg 
[    7.648896] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB0
[    7.649091] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB1
[    7.649502] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB2
[17406.327030] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[17406.329670] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[17406.334036] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[90128.405694] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB0
[90128.405987] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB1
[90132.905458] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB3
[90132.905791] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB4
[90132.906541] usb 1-2: GSM modem (1-port) converter now attached to ttyUSB5
[90148.661532] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB6
[90148.661828] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB7
[90148.662440] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB8

$ tac testdmesg | awk '$NF~/ttyUSB[0-9]+/ && !a[$NF]++ && $(NF-1)=="to" {print $NF}'
ttyUSB8
ttyUSB7
ttyUSB6
ttyUSB5
ttyUSB4
ttyUSB3
ttyUSB1
ttyUSB0

当然，sort如果您愿意，您可以将其传递下去。但是您不需要uniq(或sort -u) 它，因为 awk 应该已经处理了重复项。

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