string bash 在文件的每一行中搜索字符串
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bash search for string in each line of file
提问by Joshua Noble
I'm trying what seems like a very simple task: use bash to search a file for strings, and if they exist, output those to another file. It could be jetlag, but this should work:
我正在尝试一个看起来很简单的任务：使用 bash 搜索文件中的字符串，如果存在，将它们输出到另一个文件。这可能是时差，但这应该有效：
#!/bin/bash
cnty=CNTRY
for line in $(cat wheatvrice.csv); do
if [[ $line = *$cnty* ]]
then
echo $line >> wr_imp.csv
fi
done
I also tried this for completeness:
为了完整性，我也试过这个：
#!/bin/bash
cnty=CNTRY
for line in $(cat wheatvrice.csv); do
case $line in
*"$cnty"*) echo $line >> wr_imp.csv;;
*) echo "no";;
esac
done
both output everything, regardless of whether the line contains CNTRY or not, and I'm copy/pasting from seemingly reliable sources, so apparently there's something simple about bash-ness that I'm missing?
两者都输出所有内容，无论该行是否包含 CNTRY，而且我是从看似可靠的来源复制/粘贴的，所以显然我缺少一些关于 bash-ness 的简单内容？
回答by Ignacio Vazquez-Abrams
Don't use bash, use grep.
不要使用 bash，使用 grep。
grep -F "$cnty" wheatvrice.csv >> wr_imp.csv
回答by user unknown
While I would suggest to simply use grep too, the question is open, why you approach didn't work. Here a self referential modification of your second approach - with keyword 'bash' to match itself:
虽然我也建议简单地使用 grep，但问题是开放的，为什么你的方法不起作用。这是第二种方法的自引用修改 - 使用关键字“bash”来匹配自身：
#!/bin/bash
cnty=bash
while read -r line
do
case $line in
*${cnty}*)
echo $line " yes" >> bashgrep.log
;;
*)
echo "no"
;;
esac
done < bashgrep.sh
The keypoint is while read -r line ... < FILE. Your command with cat involves String splitting, so every single word is processed in the loop, not every line.
关键是while read -r line ... < FILE。您的 cat 命令涉及字符串拆分，因此循环中处理每个单词，而不是每一行。
The same problem in example 1.
示例 1 中的相同问题。
