bash 一次将多个字段设置为 awk 变量
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Setting multiple field to awk variables at once
提问by Nap
I am trying to set an awk variable field to several field at once.
我正在尝试将 awk 变量字段一次设置为多个字段。
Right now I can only set the variables one by one.
现在我只能一一设置变量。
for line in `cat file.txt`;do
var1=`echo $line | awk -F, '{print }'`
var2=`echo $line | awk -F, '{print }'`
var3=`echo $line | awk -F, '{print }'`
#Some complex code....
done
I think this is costly cause it parses the linux variable several times. Is there a special syntax to set the variable at once? I know that awk has a BEGIN and END block but the reason I am trying to avoid the BEGIN and END block is to avoid nested awk.
我认为这很昂贵，因为它会多次解析 linux 变量。是否有特殊的语法可以一次设置变量？我知道 awk 有一个 BEGIN 和 END 块，但我试图避免 BEGIN 和 END 块的原因是避免嵌套 awk。
I plan to place another loop and awk code in the #Some complex code.... part.
我计划在 #Some complex code.... 部分放置另一个循环和 awk 代码。
for line in `cat file.txt`;do
var1=`echo $line | awk -F, '{print }'`
var2=`echo $line | awk -F, '{print }'`
var3=`echo $line | awk -F, '{print }'`
for line2 in `cat file_old.txt`;do
vara=`echo $line2 | awk -F, '{print }'`
varb=`echo $line2 | awk -F, '{print }'`
# Do comparison of $var1,var2 and $vara,$varb , then do something with either
done
done
回答by newfurniturey
You can use the IFSinternal field separator to use a comma (instead of whitespace) and do the assignments in a whileloop:
您可以使用IFS内部字段分隔符来使用逗号（而不是空格）并在while循环中进行分配：
SAVEIFS=$IFS;
IFS=',';
while read line; do
set -- $line;
var1=;
var2=;
var3=;
...
done < file.txt
IFS=$SAVEIFS;
This will save a copy of your current IFS, change it to a ,character, and then iterate over each line in your file. The line set -- $line;will convert each word (separated by a comma) into a numeric-variable ($1, $2, etc.). You can either use these variables directly, or assign them to other (more meaningful) variable names.
这将保存当前 的副本IFS，将其更改为一个,字符，然后遍历文件中的每一行。线set -- $line;将每个字（由逗号分隔）转换成数字变量（$1，$2等）。您可以直接使用这些变量，也可以将它们分配给其他（更有意义的）变量名称。
Alternatively, you could use IFSwith the answer provided by William:
或者，您可以使用IFS威廉提供的答案：
IFS=',';
while read var1 var2 var3; do
...
done < file.txt
They are functionally identical and it just comes down to whether or not you want to explicitly set var1=$1or have it defined in the while-loop's head.
它们在功能上是相同的，这取决于您是否要var1=$1在while-loop 的头部显式设置或定义它。
回答by William Pursell
Why are you using awkat all?
你为什么要使用awk？
while IFS=, read var1 var2 var3; do
...
done < file.txt
回答by V H
#!/bin/bash
FILE="/tmp/values.txt"
function parse_csv() {
local lines=$lines;
> $FILE
OLDIFS=$IFS;
IFS=","
i=0
for val in ${lines}
do
i=$((++i))
eval var${i}="${val}"
done
IFS=$OLDIFS;
for ((j=1;j<=i;++j))
do
name="var${j}"
echo ${!name} >> $FILE
done
}
for lines in `cat file_old.txt`;do
parse_csv;
done
The problem you have described has only got 3 values, would there be a chance that 3 values may differ and be 4 or 5 or undefined ?
您描述的问题只有 3 个值，是否有可能 3 个值可能不同并且是 4 或 5 或未定义？
if so the above will parse through the csv line by line and output each value at a time on a new line in a file called /tmp/values.txt
如果是这样，上面将逐行解析 csv 并在名为 /tmp/values.txt 的文件中的新行上一次输出每个值
feel free to modify to match your requirements its far more dynamic than defining 3 values
随意修改以满足您的要求，它比定义 3 个值更具动态性
