bash sed：如何删除与包含正斜杠的模式匹配的行？
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sed: How to delete lines matching a pattern that contains forward slashes?
提问by donatello
Suppose a file /etc/fstabcontains the following:
假设一个文件/etc/fstab包含以下内容：
/dev/xvda1 / ext4 defaults 1 1
/dev/md0 /mnt/ibsraid xfs defaults,noatime 0 2
/mnt/ibsraid/varlog /var/log none bind 0 0
/dev/xvdb None auto defaults,nobootwait 0 2
I want to delete the line starting with /dev/xvdb. So I tried:
我想删除以/dev/xvdb. 所以我试过：
$ sed '/^/dev/xvdb/d' /etc/fstab
sed: -e expression #1, char 5: extra characters after command
$ sed '?^/dev/xvdb?d' /etc/fstab
sed: -e expression #1, char 1: unknown command: `?'
$ sed '|^/dev/xvdb|d' /etc/fstab
sed: -e expression #1, char 1: unknown command: `|'
None of these worked. I tried changing the delimiters to ?and |because doing this works for the sed substitution command when a pattern contains /.
这些都没有奏效。我尝试将分隔符更改为?and|因为当模式包含/.
I am using GNU Sed 4.2.1 on Debian.
我在 Debian 上使用 GNU Sed 4.2.1。
回答by John1024
You were very close. When you use a nonstandard character for a pattern delimiter, such as |pattern|, the first use of that character must be escaped:
你非常接近。当您使用非标准字符作为模式分隔符时，例如|pattern|，必须对该字符的第一次使用进行转义：
$ sed '\|^/dev/xvdb|d' /etc/fstab
/dev/xvda1 / ext4 defaults 1 1
/dev/md0 /mnt/ibsraid xfs defaults,noatime 0 2
/mnt/ibsraid/varlog /var/log none bind 0 0
Similarly, one can use:
同样，可以使用：
sed '\?^/dev/xvdb?d' /etc/fstab
Lastly, it is possible to use slashes inside of /pattern/if they are escaped in the way that you showed in your answer.
最后，/pattern/如果它们以您在答案中显示的方式转义，则可以在其中使用斜杠。
回答by donatello
After some digging, I found that it is possible to escape the /in the pattern string using \. So this works:
经过一番挖掘，我发现可以/使用\. 所以这有效：
$ sed '/^\/dev\/xvdb/d' /etc/fstab
回答by Bohemian
Why the obsession with using forward slash as your delimiter? Just use something else, like a comma:
为什么痴迷于使用正斜杠作为分隔符？只需使用其他东西，例如逗号：
sed ',^/dev/xvdb,d' /etc/fstab
or a colon:
或冒号：
sed ':^/dev/xvdb:d' /etc/fstab
Or whatever makes it easiest to read. The delimiter can be anycharacter. The convention is to use a forward slash, but when it becomes awkward, switch it to something else.
或者任何使阅读更容易的东西。分隔符可以是任何字符。约定是使用正斜杠，但当它变得尴尬时，将其切换为其他东西。
Note, if you want to changethe file itself, rather than output the result, you need the "in place" flag -i:
请注意，如果要更改文件本身，而不是输出结果，则需要“就地”标志-i：
sed -i ':^/dev/xvdb:d' /etc/fstab
