我有这两个文件file1.txt
$ cat file1.txt
I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples.
I need to run the laundry.
I need to wash the dog.
I need to get the car detailed.
和file2.txt
$ cat file2.txt
I need to buy apples.
I need to do the laundry.
I need to wash the car.
I need to get the dog detailed.
我希望使用diff命令查看文件的差异，并使用-y选项显示它。
$ diff --width=250 -y file1.txt file2.txt
I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples. | I need to buy apples.
I need to run the laundry. | I need to do the laundry.
I need to wash the dog. | I need to wash the car.
I need to get the car detailed. | I need to get the dog detailed.
我希望能够重定向上面diff的输出，但我想保持上面的格式。
我在做这件事时遇到了麻烦。可以吗？
$ echo $(diff --width=250 -y file1.txt file2.txt)
I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples. | I need to buy apples. I need to run the laundry. | I need to do the laundry. I need to wash the dog. | I need to wash the car. I need to get the car detailed. | I need to get the dog detailed.
我还想知道file1.txt中最长行中有多少个字符（包括空格）。 我尝试过以下但没有快乐。可以这样做吗？
$ wc -L file1.txt
109 file1.txt
答案 0 :(得分：0)
要确保有足够的空间来完整显示所有行，请使用：
diff --width=$(( $(cat file1.txt file2.txt|wc -L)*2+3 )) -y file1.txt file2.txt
有人可能天真地认为diff所需的宽度与每个文件中最大行长度的总和有关。事实并非如此。
要在使用echo时保留换行符，需要使用双引号：
$ echo "$(diff --width=$(( $(cat file1.txt file2.txt|wc -L)*2+3 )) -y file1.txt file2.txt)"
I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples. I need to buy apples. | I need to buy apples.
I need to run the laundry. | I need to do the laundry.
I need to wash the dog. | I need to wash the car.
I need to get the car detailed. | I need to get the dog detailed