☰

日期字符串在 true 内不更新；做循环

tag-icon • tag-icon bash shell-script date
日期字符串在 true 内不更新；做循环

我有一个简单的 bash 脚本：

#!/bin/bash

enp="$(ip route | grep "192.168.1.1" | cut -d' ' -f 3)"

while true; do
    vnstat -l -i "$enp" --style 4 --json | awk '{ print strftime("[%d/%b/%Y:%H:%M:%S]"), $0 }' >> raw/caching_server_network.json
    printf -- '-%.0s' {1..100}; echo "" >> raw/caching_server_network.json
    sleep 10
done

目前，此脚本将 strftime 附加到每个 vnstat 输出的开头，并且 strftime 在每次调用时都会更新。输出：

[04/Jan/2022:13:31:17] {"index":1012,"seconds":2024,"rx":{"ratestring":"13.59 Mbit/s","bytespersecond":1698943,"packetspersecond":15220,"bytes":3397887,"packets":30441,"totalbytes":29895276777,"totalpackets":43496469},"tx":{"ratestring":"2.81 Gbit/s","bytespersecond":350918926,"packetspersecond":233842,"bytes":701837853,"packets":467685,"totalbytes":518923724379,"totalpackets":354639132}}
[04/Jan/2022:13:31:41] {"index":1013,"seconds":2026,"rx":{"ratestring":"206.68 Mbit/s","bytespersecond":25834765,"packetspersecond":31840,"bytes":51669531,"packets":63681,"totalbytes":29946946308,"totalpackets":43560150},"tx":{"ratestring":"3.15 Gbit/s","bytespersecond":394123782,"packetspersecond":269030,"bytes":788247565,"packets":538060,"totalbytes":519711971944,"totalpackets":355177192}}

我想做的是让日期时间字符串包含毫秒。但我面临一个问题，日期输出不再更新。每次调用只是将相同的时间添加到字符串中。

我已经尝试过以下方法：

#!/bin/bash

enp="$(ip route | grep "192.168.1.1" | cut -d' ' -f 3)"

while true; do
    vnstat -l -i "$enp" --style 4 --json | awk '{ print "'"$(date +%F:%T.%3N)"'", $0 }' >> raw/caching_server_network.json
    printf -- '-%.0s' {1..100}; echo "" >> raw/caching_server_network.json
    sleep 10
done

输出：

04/Jan/2022:13:30:11.743 {"index":975,"seconds":1950,"rx":{"ratestring":"73.04 Mbit/s","bytespersecond":9130121,"packetspersecond":25590,"bytes":18260242,"packets":51181,"totalbytes":29368713172,"totalpackets":42315654},"tx":{"ratestring":"3.90 Gbit/s","bytespersecond":486961964,"packetspersecond":326200,"bytes":973923928,"packets":652400,"totalbytes":498158299423,"totalpackets":340676257}}
04/Jan/2022:13:30:11.743 {"index":976,"seconds":1952,"rx":{"ratestring":"12.23 Mbit/s","bytespersecond":1529119,"packetspersecond":17962,"bytes":3058239,"packets":35924,"totalbytes":29371771411,"totalpackets":42351578},"tx":{"ratestring":"4.18 Gbit/s","bytespersecond":522336815,"packetspersecond":346742,"bytes":1044673631,"packets":693484,"totalbytes":499202973054,"totalpackets":341369741}}

请注意上面输出中两行的日期时间是如何相同的。在使用日期调用时，如何获取每次 vnstat 调用更新的日期？

答案1

每次调用 都会更改时间vnstat，但如果vnstat输出多行，则所有行都会收到相同的时间。这是因为 shell 运行date并将其输出插入到 的参数中awk。

要获取每行的新时间戳，您需要date从内部调用awk.由于我vnstat的机器上没有，我创建了一个更简单的示例：

#! /bin/bash

while true; do
    for i in {1..3} ; do
        echo $i
        sleep .1
    done  | awk '{ system("date +%F:%T.%3N\\  | tr -d \\\\n"); print $0 }'
    printf -- '-%.0s' {1..80}; echo ""
    sleep 1
done

删除tr时间戳后面的换行符。

答案2

我不会使用 shell 循环并在每次迭代中调用一个awk, date,sleep实用程序（或更糟糕的是，每次调用命令的每一行输出），我会在可以在内部完成所有这些操作的方式中完成整个操作，例如perl：

perl -MPOSIX -MTime::HiRes=gettimeofday -e '
  while (1) {
    open CMD, "-|", @ARGV;
    while (<CMD>) {
      my ($s,$us) = gettimeofday;
      printf "%s.%03d %s", strftime("%F:%T", localtime$s), $us/1000, $_
    }
    print "-" x 100 . "\n";
    sleep 10;
  }' vnstat -l -i "$enp" --style 4 --json >> file.log

或者在zsh：

zmodload zsh/zselect
ts_format='%D{%F:%T.%3.}'
sep=${(l[80][-])}

while true; do
  vnstat -l -i "$enp" --style 4 --json |
    while IFS= read -r line; do
      print -r ${(%)ts_format} $line
    done
  echo $sep
  zselect -t 1000 # cs
done >> file.log

相关内容