Question

我有一条日志，每分钟都会收到以下数据：

ID: Unit3443 IP: 192.168.1.1 MAC: 00:20:c0:04:e8:ab
ID: Unit2222 IP: 192.168.2.2 MAC: 00:40:c0:05:e8:bc

我抓住了尾巴为-1 / File的最后一行

是否可以一口气将这两个条目分配给变量？目前我有

UnitID=`tail -1 $File|awk '{print $1}'`
UnitIP=`tail -1 $File|awk '{print $2}'`

这可行，但是它要求文件被读取两次，而我担心的是在第二次读取时，tail -1的输出将不再相同。

是否可以在该行的一次读取中同时分配这两个变量？

Answer 1

arr=( $(tail -1 "$file" | awk '{print $1, $2}') )
UnitID=${arr[0]}
UnitIP=${arr[1]}

或：

id=0
ip=1
unit=( $(tail -1 "$file" | awk '{print $1, $2}') )
echo "${unit[id]}"
echo "${unit[ip]}"

或：

line=$(tail -1 "$file" | awk '{print $1, $2}')
UnitID="${line% *}"
UnitIP="${line#* }"

Answer 2

另一种替代方法，而不是使用@Pesa建议的xdf <- read_sl2("~/Downloads/Chart 09_07_2018 [2].sl2") ## Format: sl2 ## Block size: downscan ## ............. xdf ## # A tibble: 1,308 x 22 ## channel upperLimit lowerLimit frequency waterDepth keelDepth speedGps temperature lng_enc lat_enc ## <chr> <dbl> <dbl> <chr> <dbl> <dbl> <dbl> <dbl> <int> <int> ## 1 Secondary 0 13.3 200 KHz 2.62 0.328 0.5 15.8 4433307 7003054 ## 2 DSI (Downsc… 0 13.4 200 KHz 2.62 0.328 0.5 15.8 4433307 7003054 ## 3 Primary 0 13.3 200 KHz 2.62 0.328 0.5 15.9 4433307 7003054 ## 4 Secondary 0 13.3 200 KHz 2.62 0.328 0.5 15.9 4433307 7003054 ## 5 DSI (Downsc… 0 13.4 200 KHz 2.59 0.328 0 15.8 4433307 7003054 ## 6 Secondary 0 13.3 200 KHz 2.59 0.328 0 15.8 4433307 7003054 ## 7 Secondary 0 13.3 200 KHz 2.52 0.328 0 15.9 4433307 7003054 ## 8 DSI (Downsc… 0 13.4 200 KHz 2.52 0.328 0 15.9 4433307 7003054 ## 9 Primary 0 13.3 200 KHz 2.52 0.328 0 15.8 4433307 7003054 ## 10 DSI (Downsc… 0 13.4 200 KHz 2.52 0.328 0 15.8 4433307 7003054 ## # ... with 1,298 more rows, and 12 more variables: speedWater <dbl>, track <dbl>, altitude <dbl>, ## # heading <dbl>, timeOffset <int>, headingValid <lgl>, altitudeValid <lgl>, gpsSpeedValid <lgl>, ## # waterTempValid <lgl>, positionValid <lgl>, waterSpeedValid <lgl>, trackValid <lgl>，这将是一次glimpse(xdf) ## Observations: 1,308 ## Variables: 22 ## $ channel <chr> "Secondary", "DSI (Downscan)", "Primary", "Secondary", "DSI (Downscan)", "Sec... ## $ upperLimit <dbl> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,... ## $ lowerLimit <dbl> 13.3, 13.4, 13.3, 13.3, 13.4, 13.3, 13.3, 13.4, 13.3, 13.4, 13.3, 13.4, 13.3,... ## $ frequency <chr> "200 KHz", "200 KHz", "200 KHz", "200 KHz", "200 KHz", "200 KHz", "200 KHz", ... ## $ waterDepth <dbl> 2.620, 2.620, 2.620, 2.620, 2.586, 2.586, 2.516, 2.516, 2.516, 2.516, 2.516, ... ## $ keelDepth <dbl> 0.328084, 0.328084, 0.328084, 0.328084, 0.328084, 0.328084, 0.328084, 0.32808... ## $ speedGps <dbl> 0.5, 0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.... ## $ temperature <dbl> 15.84112, 15.84112, 15.86293, 15.86293, 15.79128, 15.79128, 15.86293, 15.8629... ## $ lng_enc <int> 4433307, 4433307, 4433307, 4433307, 4433307, 4433307, 4433307, 4433307, 44333... ## $ lat_enc <int> 7003054, 7003054, 7003054, 7003054, 7003054, 7003054, 7003054, 7003054, 70030... ## $ speedWater <dbl> 0.5, 0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.... ## $ track <dbl> 4.974188, 4.974188, 4.974188, 4.974188, 4.974188, 4.974188, 4.974188, 4.97418... ## $ altitude <dbl> 324.7375, 324.7375, 324.7375, 324.7375, 324.8687, 324.8687, 324.8687, 324.868... ## $ heading <dbl> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,... ## $ timeOffset <int> 1317703, 1317706, 1318036, 1318905, 1318946, 1318982, 1319130, 1319140, 13192... ## $ headingValid <lgl> FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, ... ## $ altitudeValid <lgl> TRUE, FALSE, FALSE, FALSE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, TRUE, FAL... ## $ gpsSpeedValid <lgl> TRUE, FALSE, FALSE, FALSE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, TRUE, FAL... ## $ waterTempValid <lgl> FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, ... ## $ positionValid <lgl> FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, ... ## $ waterSpeedValid <lgl> FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, ... ## $ trackValid <lgl> FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, ...并使用两次结果，以避免在read之间更改文件时出现问题

tail

注意：我也将示例更改为使用tail而不是反引号-的工作方式相同，但更容易理解。

Answer 3

您可以这样做：

dput

测试结果

df2 <- tibble(
  id = rep(1:9, each = 5, times = 2),
  date = rep(seq(as.POSIXct("2018-01-01 00:00:00"), by = "month", length.out = 5), times = 18),
  band = rep(c("b1", "b2"), each = 45),
  value = c(rnorm(45, 0), rnorm(45, 1))
)

正如@EdMorton在评论中所指出的那样，并非所有read UnitID UnitIP < <(awk 'END{print $2, $4}' file)变体都将$ 0 .. $ NF变量保留在echo $UnitID Unit2222 echo $UnitIP 192.168.2.2部分中，因此希望以下内容可以更广泛地应用：

awk

使用awk一次分配两个变量

3 个答案: