bash 创建带日期的文件名时，shell 脚本中出现不明确的重定向错误
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Ambiguous redirect error in shell scripting when creating file name with date
提问by Gabor
I'm trying to make this temperature log in Raspberry Pi happen (though some of the code did not work therefore I used slightly diff. solutions):
我正在尝试在 Raspberry Pi 中生成此温度日志（尽管某些代码不起作用，因此我使用了稍微不同的解决方案）：
https://www.raspberrypi.org/learning/temperature-log/worksheet/
https://www.raspberrypi.org/learning/temperature-log/worksheet/
I'm stuck with writing the results in a file. I want to create a file that's name contains the actual date, e.g. temperature_log_2016_08_13.txt
我坚持将结果写入文件。我想创建一个名称包含实际日期的文件，例如 temperature_log_2016_08_13.txt
When running the script I get an ambiguous redirection erroreach time lines with the echo commands execute. I tried all sort of combinations with quotes, double-quotes, no quotes. Pls advice.
运行脚本时，每次执行带有回显命令的行时，我都会收到一个不明确的重定向错误。我尝试了各种带引号、双引号和无引号的组合。请建议。
#!/bin/bash
timestamp() {
date +%F_%H-%M-%S
}
temperature() {
/opt/vc/bin/vcgencmd measure_temp
}
temp=$(temperature)
temp2=${temp:5:9}
echo Temperature Log_$(date) >/home/pi/logs/temperature_log_$(date).txt
for i in {1..5}
do
echo ${temp2} $(timestamp) >>/home/pi/logs/temperature_log_$(date).txt
sleep 1
done
UPDATE: by putting the file name between quotation marks, as advised below, the ambiguous redirect error is gone, but instead the script produces 5 files with the date/timestamp in its name. I need only 1 file into which all the temperatures are written.
更新：通过将文件名放在引号之间，如下所示，不明确的重定向错误消失了，而是脚本生成了 5 个文件，其名称中带有日期/时间戳。我只需要 1 个文件，所有温度都写入其中。
回答by eckes
The $(date)in your example produces a timestamp with blanks. You might either use your function ($(timestamp)) instead, or quote the whole target filename (or both):
在$(date)你的榜样产生用空格时间戳。您可以改用您的函数 ( $(timestamp))，或者引用整个目标文件名（或两者）：
echo bla >> "/home/pi/logs/temperature_log_$(timestamp).txt"
And it is best to actually evaluate the timestamp in the filename only before the loop, otherwise you get a new file every second or minute:
最好只在循环之前实际评估文件名中的时间戳，否则每秒钟或每分钟都会得到一个新文件：
# %F: full date; same as %Y-%m-%d
logfile = "/home/pi/logs/temperature_log_$(date +%F).txt"
echo "Temperature Log_$(date)" > "$logfile" # overwrite if started 2 times a day
for i in {1..5}
do
temp=$(/opt/vc/bin/vcgencmd measure_temp)
temp=${temp:5:9}
echo "${temp} $(timestamp)" >> "$logfile"
sleep 1
done
回答by choroba
Output of datecontains spaces. You need to doublequote the filename to make the spaces part of it:
输出date包含空格。您需要双引号文件名以使其成为空格的一部分：
echo Temperature Log_$(date) > "/home/pi/logs/temperature_log_$(date).txt"
Or use your function, but quoting the file name is a good habit anyway.
或者使用你的函数，但无论如何引用文件名是一个好习惯。
