英文:
Take value from each line of a file and search for it in another file in Unix?
问题
I have two files. I want my Unix code to take each first column from each line of File A as a variable and look for it in File B. If found, I want the found line in File B to be saved in an output file.
File A:
1335 skrgrsjgls 1231
12213 23rerwsdf 9605
11567 4693460 0340592
54321 293402460 324
File B:
-54321 Apples
-23453 Grapes
-1335 Pears
-65363 Pineapples
-96506 Grapefruit
Expected Output File:
-1335 Pears
-54321 Apples
英文:
I have two files. I want my Unix code to take each first column from each line of File A as a variable and look for it in File B. If found, I want the found line in File B to be saved in an output file.
File A:
1335 skrgrsjgls 1231
12213 23rerwsdf 9605
11567 4693460 0340592
54321 293402460 324
File B:
-54321 Apples
-23453 Grapes
-1335 Pears
-65363 Pineapples
-96506 Grapefruit
Expected Output File:
-1335 Pears
-54321 Apples
Code I have tried:
for i in $(cat File A); do grep -w $i File B > FileC; done
I get no result for this. Please any help is appreciated.
答案1
得分: 1
I hope it works for you. This could be done with grep command which is used to search patterns in the file.
OUTPUT
这个希望对你有帮助。这可以使用 `grep` 命令来完成，该命令用于在文件中搜索模式。
this one is the output for yours tested command.
这是您测试的命令的输出。
英文:
I hope it works for you. This could be done with grep command which is used to search patterns in the file.
for i in $(cat FileA.txt); do grep -i "$i" FileB.txt >> output.txt; done
OUTPUT
HaLF-MenTaL@DESKTOP-7B47GH0 MINGW64 ~/Documents
$ for i in $(cat FileA.txt); do grep -i "$i" FileB.txt >> output.txt; done
HaLF-MenTaL@DESKTOP-7B47GH0 MINGW64 ~/Documents
$ cat output.txt
-1335 Pears
-54321 Apples
this one is the output for yours tested command.
HaLF-MenTaL@DESKTOP-7B47GH0 MINGW64 ~/Documents
$ for i in $(cat FileA.txt); do grep -i "$i" FileB.txt | head -10; done
-1335 Pears
-54321 Apples
答案2
得分: 1
对于大文件，你应该避免在每一行中使用新的grep循环。
awk是一个很好的工具，另一个解决方案是：
grep -f <(sed -r 's/([^ ]*).*/^- /' FileA) FileB
部分 <(sed -r 's/([^ ]*).*/^-\1 /' FileA) 创建了一个类似于内存中的字符串文件，其中包含你想要查找的字符串（以 ^ 开头，连字符，数字，空格），
而 grep -f file 使用 "file" 作为要查找的多个字符串。
英文:
For large files you should avoid loops with a new grep for each line.
awk is a great tool, an other solution is
grep -f <(sed -r 's/([^ ]*).*/^- /' FileA) FileB
The part <(sed -r 's/([^ ]*).*/^-\1 /' FileA) is creating a kind of in-memory file of strings you want to look for (start of line with ^, hyphen, number, space),
and grep -f file uses the "file" as multiple strings to look for.
答案3
得分: 1
好的，以下是已解决我的问题的内容。我感谢所有为这个问题做出贡献的人，我相信他们的版本也有效。
while read -r line; do var=$(echo $line | awk '{print $1}') grep -w "$var" FileB > FileC; done < FileA
英文:
Okay, so the following solved my problem. I thank everyone who contributed to the question and I am sure their version also works.
while read -r line; do var=$(echo $line | awk '{print $1}') grep -w "$var" FileB > FileC; done < FileA
答案4
得分: 1
我同意应该避免在处理大文件时使用循环，并且awk是一个很好的替代方案。尝试使用以下命令：
awk 'FNR==NR { a[$1]=$0; next } $1 in a { print a[$1] }' FileB.txt FileA.txt > Output.txt
其中：
FNR==NR部分确保下一个块仅对第一个文件执行，{ a[$1]=$0; next }会将 FileB.txt 的第一列保存为数组，$1 in a会检查该键是否存在于 FileA.txt 中，{ print a[$1] }打印找到的匹配项，FileB.txt FileA.txt是命令行中提供的参数（注意顺序），> Output.txt将打印内容保存到输出文件中。
英文:
I agree that loops should be avoided for large files and that awk is a good alternative. Try doing:
awk 'FNR==NR { a[$1]=$0; next } $1 in a { print a[$1] }' FileB.txt FileA.txt > Output.txt
The FNR==NR part ensure that the next block is only executed for the first file,
{ a[$1]=$0; next } will save the first col of FileB.txt as an array,
$1 in a will check if that key exists in FileA.txt,
{ print a[$1] } prints the matches that are found,
FileB.txt FileA.txt are the arguments given to the cmd line (careful with the order),
and > Output.txt saves that print to an output file.
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