如何转义从文件获取的内容中的双引号

Question

statusfile.log我在从到添加内容时尝试转义双引号statusfile_truncated.log。

我四处寻找，但越来越困惑。您将如何实现它？

这是我目前得到的：

#!/bin/bash

statusfile="statusfile.log"
statusfile_truncated="statusfile_truncated.log"
tail -n 50 $statusfile >> $statusfile_truncated

statusfile.log的内容：

2017-05-15 22:36:18 test.somedomain.com <--- 250 CWD successful. "/xxxxxxxxxxxxx" is current directory.
2017-05-15 22:36:18 test.somedomain.com <--- 250 CWD successful. "/xxxxxxxxxxxxx" is current directory.
2017-05-15 22:36:18 test.somedomain.com <--- 250 CWD successful. "/xxxxxxxxxxxxx" is current directory.

statusfile_truncated.log 的内容应该是：

2017-05-15 22:36:18 test.somedomain.com <--- 250 CWD successful. \"/xxxxxxxxxxxxx\" is current directory.
2017-05-15 22:36:18 test.somedomain.com <--- 250 CWD successful. \"/xxxxxxxxxxxxx\" is current directory.
2017-05-15 22:36:18 test.somedomain.com <--- 250 CWD successful. \"/xxxxxxxxxxxxx\" is current directory.

Answer 1

如果您只想在双引号前插入一个反斜杠，您可以sed这样做：

sed 's/"/\\"/g' $statusfile >> $statusfile_truncated

但如果要真正逃脱，还应该考虑其他工具和技术。

Answer 2

引用字符串的最佳方式bash是使用%b选项 in printf。这将处理所有特殊字符：

$ variablename='foo "bar and C:\\foo\\bar'
$ printf '%b\n' "$variablename"
foo "bar and C:\foo\bar