bash 逐行读取文件 -> 搜索另一个文本文档中的每一行，如果匹配，则输出到另一个文本文件
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Read a file line by line -> search for each line in another text document, if match, output to another text file
提问by eveo
I have a script that takes two parameters.
我有一个需要两个参数的脚本。
ls > .txt
ls > .txt
I now have a.txt ($1 is directory 'a', $2 is directory 'b') and b.txt each with their contents listed inside them. What I want to do is search line by line in a.txt and see if there is a match in b.txt.
我现在有 a.txt（$1 是目录 'a'，$2 是目录 'b'）和 b.txt，其中每个都列出了它们的内容。我想要做的是在a.txt中逐行搜索，看看b.txt中是否有匹配项。
If I have these files in a.txt:
如果我在 a.txt 中有这些文件：
file1 -> search for file1 in b.txt, if match, output to a_match.txt
file2 -> search for file2 in b.txt, if match, output to a_match.txt
file3 -> search for file3 in b.txt, if match, output to a_match.txt
Vice versa for b.txt. How would I do this? Also, not looking for alternative methods to doing this, there are soooo many other ways to check differences amongst directories, but this is the only acceptable way for my assignment :(
b.txt 反之亦然。我该怎么做？此外，不是在寻找替代方法来执行此操作，还有很多其他方法可以检查目录之间的差异，但这是我分配的唯一可接受的方法:(
采纳答案by Charlie Martin
Okay, this is clearly homework so I'm not going to give you a full solution. Here's the outline
好的，这显然是家庭作业，所以我不会给你一个完整的解决方案。这是大纲
while "there are lines left in the file, read a line" do
grep "the line" "the file"
done
the key for getting lines is the readcommand. Do help readin bash for details.
获取行的关键是read命令。不要help read在bash了解详情。
Update
更新
Okay, so let's look a little more closely. Start the script with
好的，让我们仔细看看。启动脚本
Let's call the script a.bash. You'll want to run it as
我们将脚本称为 a.bash。你会想要运行它
$ a.bash b.txt < a.txt > a_match.txt
a.bashis a script that reads line from a.txt, searches in b.txtand sends output to STDOUT which you then direct into your file a_match.txt .
a.bash是一个脚本，它从 a.txt 读取行，搜索b.txt并将输出发送到 STDOUT，然后您将其定向到您的文件 a_match.txt 中。
Start the script witha "shebang line'. Usually it's
以“shebang line”开始脚本。通常是
#!/usr/bin/bash --
or something similar.
或类似的东西。
The readprimitive simply reads a line into a variable, and by default reads into a variable named REPLY. So "there are lines left in the file, read a line" is simply
该read原始简单的读取一行到一个变量，并且默认读取到一个变量命名的答复。所以“文件中还有行，读取一行”很简单
while read
The name of the file to search in will be in the special shell variable $1, representing the first argument. Since the other names are used in redirection, they don't appear as arguments at all.
要搜索的文件名将在特殊的 shell 变量 $1 中，代表第一个参数。由于其他名称用于重定向，因此它们根本不作为参数出现。
Now, the command grep(1)searches a file for a string and put's the line on which the string occurs onto STDOUT. So all we need for the search is
现在，命令grep(1)在文件中搜索字符串并将出现字符串的行放到 STDOUT 上。所以我们搜索所需的只是
grep $REPLY b.txt
(Read the man page for grep.)
（阅读grep的手册页。）
Since grep(1)puts the output on STDOUT anyway, it'll go out and be redirected into a_matches.txt. That's your "grep the line in the file" line.
由于grep(1)无论如何都会将输出放在 STDOUT 上，因此它将出去并被重定向到a_matches.txt. 那是您的“grep 文件中的行”行。
Now just fit that all together.
现在只需将它们组合在一起即可。
Quiz:
测验：
- Why is it
$REPLY? How would you change the script so you could call it as:
$ a.bash a.txt b.txt a_matches.txt
- 为什么
$REPLY？ 您将如何更改脚本，以便您可以将其称为：
$ a.bash a.txt b.txt a_matches.txt
回答by freiheit
Here's a quick solution that I think meets your requirements:
这是我认为满足您要求的快速解决方案：
fgrep -x -f b.txt a.txt > a_match.txt
回答by Algorithmist
This could help you just go through the tutorial and it bests meet your requirements.Again there is not just one way to read a file line by line and some are faster than others and some are more intuitive than others.
这可以帮助您完成本教程，它最能满足您的要求。同样，逐行读取文件的方法不止一种，有些方法比其他方法快，有些方法比其他方法更直观。
http://www.unix.com/tips-tutorials/18009-12-ways-parse-file.html
http://www.unix.com/tips-tutorials/18009-12-ways-parse-file.html
回答by Paused until further notice.
This is what I would use:
这就是我会使用的：
diff dir1/ dir2/
or
或者
diff "" ""
