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。
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
给定test.txt文件包含"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
cut -b19-20 test.txt > test1.txt # This will extract chars 19 & 20 "ST"
while read -r; do;
> x=$REPLY
> done < test1.txt
echo $x
ST
其他回答
使用sed replace的简单方法:
result=$(echo "someletters_12345_moreleters.ext" | sed 's/.*_\(.*\)_.*/\1/g')
echo $result
有点晚了,但我刚刚遇到了这个问题,并发现了以下内容:
host:/tmp$ 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
如果有人想要更严格的信息,你也可以像这样在man bash中搜索
$ man bash [press return key]
/substring [press return key]
[press "n" key]
[press "n" key]
[press "n" key]
[press "n" key]
结果:
${parameter:offset} ${parameter:offset:length} Substring Expansion. Expands to up to length characters of parameter starting at the character specified by offset. If length is omitted, expands to the substring of parameter start‐ ing at the character specified by offset. length and offset are arithmetic expressions (see ARITHMETIC EVALUATION below). If offset evaluates to a number less than zero, the value is used as an offset from the end of the value of parameter. Arithmetic expressions starting with a - must be separated by whitespace from the preceding : to be distinguished from the Use Default Values expansion. If length evaluates to a number less than zero, and parameter is not @ and not an indexed or associative array, it is interpreted as an offset from the end of the value of parameter rather than a number of characters, and the expan‐ sion is the characters between the two offsets. If parameter is @, the result is length positional parameters beginning at off‐ set. If parameter is an indexed array name subscripted by @ or *, the result is the length members of the array beginning with ${parameter[offset]}. A negative offset is taken relative to one greater than the maximum index of the specified array. Sub‐ string expansion applied to an associative array produces unde‐ fined results. Note that a negative offset must be separated from the colon by at least one space to avoid being confused with the :- expansion. Substring indexing is zero-based unless the positional parameters are used, in which case the indexing starts at 1 by default. If offset is 0, and the positional parameters are used, $0 is prefixed to the list.
基于jor的回答(这对我来说并不适用):
substring=$(expr "$filename" : '.*_\([^_]*\)_.*')
Inklusive end,类似于JS和Java实现。删除+1如果你不想这样做。
function substring() {
local str="$1" start="${2}" end="${3}"
if [[ "$start" == "" ]]; then start="0"; fi
if [[ "$end" == "" ]]; then end="${#str}"; fi
local length="((${end}-${start}+1))"
echo "${str:${start}:${length}}"
}
例子:
substring 01234 0
01234
substring 012345 0
012345
substring 012345 0 0
0
substring 012345 1 1
1
substring 012345 1 2
12
substring 012345 0 1
01
substring 012345 0 2
012
substring 012345 0 3
0123
substring 012345 0 4
01234
substring 012345 0 5
012345
更多示例调用:
substring 012345 0
012345
substring 012345 1
12345
substring 012345 2
2345
substring 012345 3
345
substring 012345 4
45
substring 012345 5
5
substring 012345 6
substring 012345 3 5
345
substring 012345 3 4
34
substring 012345 2 4
234
substring 012345 1 3
123