bash 如何在 a 是变量赋值的行中对子字符串进行 GREP？
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How to GREP a substring in a line which a is variable assignment?
提问by Lev Levitsky
I have an output which is of the format
我有一个格式的输出
OK: CpuUser=0.11; CpuNice=0.00; CpuSystem=0.12; CpuIowait=0.02; CpuSteal=0.00;
确定：CpuUser=0.11；CpuNice=0.00；中央处理器=0.12；CPUIowait=0.02；CpuSteal=0.00;
I want to get just the CpuIowait=0.12 as output. I want to grep just a specific substring. How do I do that?
我只想得到 CpuIowait=0.12 作为输出。我只想 grep 一个特定的子字符串。我怎么做？
回答by ruakh
You can use the -o("only") flag. This command:
您可以使用-o("only") 标志。这个命令：
grep -o 'CpuIowait=[^;]*'
will print out the specific substrings that match CpuIowait=[^;]*, instead of printing out the whole lines that contain them.
将打印出匹配的特定子字符串CpuIowait=[^;]*，而不是打印出包含它们的整行。
回答by Lev Levitsky
If you want to use grep, try something like this:
如果要使用grep，请尝试以下操作：
echo "OK: CpuUser=0.11; CpuNice=0.00; CpuSystem=0.12; CpuIowait=0.02; CpuSteal=0.00;" | grep -oE "CpuIowait=[[:digit:]]*\.[[:digit:]]*"
回答by xtopher
If you're not dead set on using grep, you can pipe the input to sed:
如果您不是死心塌地使用grep，则可以将输入通过管道传输到sed：
sed -ne "s/^.*\(CpuSystem=[0-9.]*\);.*$//p;"
From man sed:
来自man sed：
-n, --quiet, --silent: suppress automatic printing of pattern space
-e script, --expression=script: add the script to the commands to be executed
-n, --quiet, --silent: 抑制模式空间的自动打印
-e script, --expression=script: 将脚本添加到要执行的命令中
回答by jordanm
To get the entire string:
要获取整个字符串：
var=$(grep -Eo 'CpuIowait=[0-9]{1,2}[.][0-9]{2}' < <(command))
To get just the value, if you have GNU grep with -P, you can use the following:
要获得该值，如果您有带 -P 的 GNU grep，则可以使用以下命令：
var=$(grep -Po '(?<=CpuIowait=).*(?=;)' < <(command))
Using awk:
使用 awk：
var=$(awk -F'; |: ' '{ for (i=0;i<=NF;i++) { split($i,arr,/=/); if (arr[1] == "CpuIowait") { print arr[2] } } }' < <(command))
Using pure bash:
使用纯 bash：
output=$(command)
[[ $output =~ (CpuIowait=[0-9][.][0-9]{2}) ]] && echo "${BASH_REMATCH[1]}"
