Question

说我想将file_b.txt的内容附加到file_a.txt。但仅当file_a.txt尚未包含file_b.txt的内容时。我如何首先在第一个文件中搜索第二个文件的内容？

所以给定file_a.txt：

the quick
brown fox

和file_b.txt：

jumped over
the lazy
dog

和script.sh的开头：

#!/bin/bash

# make sure file_b.txt isn't already in file_a.txt, then:
cat file_b.txt >> file_a.txt

无论执行script.sh多少次，我怎样才能确保我最终得到这个？

the quick
brown fox
jumped over
the lazy
dog

Answer 1

也许你可以试试diff，就像这样。

#!/bin/sh

diff <(tail -$(wc -l file_b.txt | awk '{print $1}') file_a.txt) file_b.txt 
is_appended=$?
if is_appended ; then
  exit 1;  # file_b.txt has been appended.
else
  cat file_b.txt >> file_a.txt
fi

exit 0

Answer 2

你可以做一个嵌套的while循环来实现所需的结果

#!/usr/bin/env bash

isNotReadInFile=0;

while read secondFile;do
    while read firstFile;do
        [[ "${firstFile}" != "${secondFile}" ]] && {
            isNotReadInFile=1;
        }
    done < ./file_a.txt

    (( isNotReadInFile == 1 )) && {
        echo "${secondFile}" >> ./file_a.txt;
        isNotReadInFile=0;
    }

done < ./file_b.txt

Answer 3

与：bash text search: find if the content of one file exists in another file中的建议相似你可以用

grep -q -f file_a.txt file_b.txt

全文

editor cat_if_not_already_there.sh

粘贴

#!/bin/bash

file1=$1
file2=$2
if grep -q -f  $file1 $file2 ;
then
    cat $file1 # already contains the text
else
    cat $file1 $file2 # ok concat
fi

制作可执行文件

chmod u+x cat_if_not_already_there.sh

准备测试文件

echo -e "the quick\nbrown fox" >file_a.txt
echo -e "jumped over\nthe lazy\ndog" >file_b.txt
cat file_a.txt file_b.txt > file_c.txt

期待cat被执行

./cat_if_not_already_there.sh file_a.txt file_b.txt 
the quick
brown fox
jumped over
the lazy
dog

[OK]

预计cat不会被执行

./cat_if_not_already_there.sh file_c.txt file_b.txt 
the quick
brown fox
jumped over
the lazy
dog

[OK]

向观众提问

./cat_if_not_already_there.sh file_c.txt file_a.txt表现如预期吗？
./cat_if_not_already_there.sh file_b.txt file_b.txt表现如预期吗？
./cat_if_not_already_there.sh file_a.txt file_c.txt表现如预期吗？

如何在文件中搜索其他文件的内容？

3 个答案: