The modifier causes ^ and $ to match respectively (in addition to the normal behavior) the empty string after a newline, and the empty string before a newline. Next time Next time, in the final article of this series on sed, I’ll show you lots of excellent real-world examples of using sed for many different kinds of tasks. Fortunately, there is an easy way to fix this. Like q, it provides the ability to return an exit code to the caller. The character . (dot) matches any single character. The word-boundery expression (‘\b’) at both ends ensures partial words are not matched (e.g. ‘the then’ is not a desired match). The -E option enables extended regular expression syntax, alleviating the need to add backslashes before the parenthesis.
See Extended regular expressions. -s —separate By default, sed will consider the files specified on the command line as a single continuous long stream. You may want to think about how you’d have approached this problem using your favorite scripting language — could you have easily fit the solution in one line?Mixing things up As we begin creating more complex sed scripts, we need the ability to enter more than one command. Use -i to edit files in-place instead of printing to standard output. The label may be omitted, in which case the next cycle is started. t label Branch to label only if there has been a successful substitution since the last input line was read or conditional branch was taken. Note: when both the p and e options are specified, the relative ordering of the two produces very different results. In general, ep (evaluate then print) is what you want, but operating the other way round can be useful for debugging. Most characters are ordinary: they stand for themselves in a pattern, and match the corresponding characters.
Note that the regular expression matcher is greedy, i.e., matches are attempted from left to right and, if two or more matches are possible starting at the same character, it selects the longest. Then, sed proceeds to line 2, and repeats the process. Note that this is the only place where the 0 address makes sense; there is no 0-th line and commands which are given the 0 address in any other way will give an error. Regular expressions in sed are specified between two slashes.