Home / ubuntu / Questions / 1008738
Accepted
Josef Klimuk
Asked: 2018-02-23 06:43:38 +0800 CST

Why am I getting the error "missing terminating ] for character class"?

  • 772

I want to cut a string with brackets using sed.

How to avoid an error if I want to drop a string with [? For example:

$ echo '[Om/mystring' | grep -oP '(?<=[Om\\)\w+'
grep: missing terminating ] for character class
command-line regex grep text-processing

2 Answers

  1. Best Answer

    As the error missing terminating ] for character class already says, the problem here has to do with [, which you need to escape. Otherwise, it is understood as a character class by grep.

    Also, you are saying //, while you want to use / instead of \ according to your input.

    All together, this prints a set of words after [Om/:

    $ echo '[Om/mystring' | grep -oP '(?<=\[Om\/)\w+'
mystring
    • 10

  2. You are getting the error because [ is a special character in regular expression syntax, introducing a character class. To be treated as a string literal, it must be escaped i.e. \[

    If you just want to remove the [Om/ prefix, then it's simpler sed if you use a delimiter that doesn't appear in the pattern:

    $ echo '[Om/mystring' | sed 's;\[Om/;;'
mystring
    • 6