UNIX BASH：从字符串中提取数字
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UNIX BASH: extracting number from string
提问by Albinoswordfish
This is probably a very simple question to an experienced person with UNIX however I'm trying to extract a number from a string and keep getting the wrong result.
对于有 UNIX 经验的人来说，这可能是一个非常简单的问题，但是我试图从字符串中提取一个数字并不断得到错误的结果。
This is the string:
这是字符串：
8962 ? 00:01:09 java
This it the output I want
这是我想要的输出
8962
But for some reason I keep getting the same exact string back. This is what I've tried
但出于某种原因，我一直在取回完全相同的字符串。这是我试过的
pid=$(echo $str | sed "s/[^[0-9]{4}]//g")
If anybody could help me out it would be appreciated.
如果有人可以帮助我，将不胜感激。
回答by Peter Tillemans
There is more than one way to skin a cat :
给猫剥皮的方法不止一种：
pti@pti-laptop:~$ echo 8962 ? 00:01:09 java | cut -d' ' -f1
8962
pti@pti-laptop:~$ echo 8962 ? 00:01:09 java | awk '{print }'
8962
cut cuts up a line in different fields based on a delimeter or just byte ranges and is often useful in these tasks.
cut 根据分隔符或仅字节范围在不同字段中剪切一行，并且在这些任务中通常很有用。
awk is an older programming language especially useful for doing stuff one line at a time.
awk 是一种较旧的编程语言，特别适用于一次一行地做事情。
回答by ghostdog74
Shell, no need to call external tools
Shell，无需调用外部工具
$ s="8962 ? 00:01:09 java"
$ IFS="?"
$ set -- $s
$ echo
8962
回答by Paused until further notice.
Pure Bash:
纯重击：
string='8962 ? 00:01:09 java'
pid=${string% \?*}
Or:
或者：
string='8962 ? 00:01:09 java'
array=($string)
pid=${array[0]}
回答by Sean
I think this is what you want:
我想这就是你想要的：
pid=$(echo $str | sed 's/^\([0-9]\{4\}\).*//')
回答by Fritz G. Mehner
Pure Bash:
纯重击：
string="8962 ? 00:01:09 java"
[[ $string =~ ^([[:digit:]]{4}) ]]
pid=${BASH_REMATCH[1]}
回答by Crayon Violent
/^[0-9]{4}/matches 4 digits at the beginning of the string
/^[0-9]{4}/匹配字符串开头的 4 位数字
