bash - 如何在 BASH 中使用 `while read -r line` 同时检查另一个文件是否为空？

Question

我有一个 while 循环，简化如下:

while read -r line
do
    (delete some lines from file2.txt)
done < file.txt

如果 file2.txt 为空，则此 while 循环不再需要运行。

换句话说，我需要这个:

while read -r line AND file2.txt IS NOT EMPTY
do
    (delete some lines from file2.txt
done < file.txt

我尝试将 while read -r line 与 -s file2.txt 结合使用，但结果不起作用:

while [ read -r line ] || [ -s file2.txt ]
do
    (delete some lines from file2.txt)
done < file.txt

我如何使用这个 while 循环来读取文件中的行，同时检查另一个文件是否为空？

Answer 1

将阅读和测试结合为:

while read -r line && [ -s file2.txt ]
do
  # (delete some lines from file2.txt)
  echo "$line"
done <file.txt

这将在循环的每次迭代之前检查 file2.txt 是否为非空。