如何仅从文件名中提取一个下划线分隔的字段? [英] How can I just extract one underbar-separated field from a filename?

问题描述

我有一个像这样的文件名列表:

I have a list of file names like this:

REG_2016120200hourly_d01_20161202_00_00_00.nc

我要提取这个名字并放入一个变量:

Of this name I would like to extract and put in a variable:

1)日期20161202

1)date 20161202

    for file in /path/*;
    do
     filename=$(basename -- "$file")
     date=${filename:4:8}
     echo $date
    done

这有效，脚本给了我 20161202 ，我不知道为什么

and this is working, the script give me 20161202 and I don't know why

2)时间步00

我需要先取两个零0，然后尝试使用

I need to take the firsts two zero 00 and I'm trying with

timestep = $ {filename:34:36} ，但这不起作用.

我有点惊讶，因为我在其他脚本中使用了相同的方法，但是我从未遇到过问题.

I'm a little bit surprised because I used the same method in other scripts and I have never had problems.

谢谢

推荐答案

timestep="${filename:34:2}"

2 是长度.

来自 man bash :

$ {parameter:offset:length} :子字符串扩展.从offset指定的字符开始，扩展到参数值的最大长度字符.[...]

${parameter:offset:length}: Substring Expansion. Expands to up to length characters of the value of parameter starting at the character specified by offset. [...]

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