给定someletters_12345_moreleters形式的文件名。ext，我想提取5位数字，并将它们放入一个变量。
为了强调这一点，我有一个x个字符的文件名，然后是一个5位数字序列，两边都有一个下划线，然后是另一组x个字符。我想把这个5位数代入一个变量。
我对实现这一目标的多种不同方式非常感兴趣。
当前回答
类似于php中的substr('abcdefg'， 2-1, 3):
echo 'abcdefg'|tail -c +2|head -c 3
其他回答
基于jor的回答(这对我来说并不适用):
substring=$(expr "$filename" : '.*_\([^_]*\)_.*')
以下是我的做法:
FN=someletters_12345_moreleters.ext
[[ ${FN} =~ _([[:digit:]]{5})_ ]] && NUM=${BASH_REMATCH[1]}
解释:
Bash-specific:
[[]]为条件表达式 =~表示条件为正则表达式 如果前一个命令成功，&&将链接这些命令
正则表达式(RE): _([[:digit:]]{5})_
_是字面量，用于为被匹配的字符串划分/锚定匹配边界 ()创建捕获组 [[:digit:]]是一个字符类，我认为它不言自明 {5}表示前面的字符中的恰好五个，类(如本例中所示)或组必须匹配
In english, you can think of it behaving like this: the FN string is iterated character by character until we see an _ at which point the capture group is opened and we attempt to match five digits. If that matching is successful to this point, the capture group saves the five digits traversed. If the next character is an _, the condition is successful, the capture group is made available in BASH_REMATCH, and the next NUM= statement can execute. If any part of the matching fails, saved details are disposed of and character by character processing continues after the _. e.g. if FN where _1 _12 _123 _1234 _12345_, there would be four false starts before it found a match.
外壳切割-从字符串中打印特定范围的字符或给定部分
#method1)使用bash
str=2020-08-08T07:40:00.000Z
echo ${str:11:8}
#方法2)使用cut
str=2020-08-08T07:40:00.000Z
cut -c12-19 <<< $str
#method3)当使用awk时
str=2020-08-08T07:40:00.000Z
awk '{time=gensub(/.{11}(.{8}).*/,"\\1","g",$1); print time}' <<< $str
有点晚了，但我刚刚遇到了这个问题，并发现了以下内容:
host:/tmp$ asd=someletters_12345_moreleters.ext
host:/tmp$ echo `expr $asd : '.*_\(.*\)_'`
12345
host:/tmp$
我用它在一个没有%N日期的嵌入式系统上获得毫秒分辨率:
set `grep "now at" /proc/timer_list`
nano=$3
fraction=`expr $nano : '.*\(...\)......'`
$debug nano is $nano, fraction is $fraction
也许这可以帮助你得到想要的输出
代码:
your_number=$(echo "someletters_12345_moreleters.ext" | grep -E -o '[0-9]{5}')
echo $your_number
输出:
12345
