CODEWITHSUNDEEP
regexlinuxshellsed
Pullingmyhairout
Pullingmyhairout

Reputation: 775

Combine these two regex patterns

I have two regex values that I have been trying to combine into a single statement however it is not working properly. I need to be able to display lines that have comments in them or start with a blank space and then have the comments.

ie. 

/* comment 

      /* comment

sed -n "/\(^[/*]\).*\([*/]$\)/ p" testfile

sed -n "/^\s/ p" testfile

I have been trying using the | statement however it is not working.

Is it possible to merge them into one or do I need to run them separately.

Thanks

Upvotes: 0

Views: 117

Answers (4)

Walter A
Walter A

Reputation: 20002

You can use grep:

grep "^ */\*" testfile

^=start of line First * is repeating the space 0 or more times Second star is escaped, so that is a real one.

Upvotes: 1

Michael Vehrs
Michael Vehrs

Reputation: 3363

As the other answers illustrate, it is often possible to find a regular expression general enough to match everything your original expressions matched. In fact, this is always possible, since you can always combine two expressions like this:

(regex_1|regex_2|...|regex_n)

(Depending on the dialect you use, you might have to use backslashes.) However, a sed program may consist of several statements, so your example could be simply rewritten as:

sed -n "/\(^[/*]\).*\([*/]$\)/p /^\s/p" testfile

Upvotes: 1

Pedro Lobito
Pedro Lobito

Reputation: 98901

You can try : 

/^[ ]*(\/\*.*)$/

The regex above will match any lines with comments, that can start with spaces, and capture the line to a group. Check the Regex Demo

Regex Explanation

/^[ ]*(\/\*.*)$/

    ^ assert position at start of a line
    [ ]* match a single character present in the list below
        Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
         the literal character  
    1st Capturing group (\/\*.*)
        \/ matches the character / literally
        \* matches the character * literally
        .* matches any character (except newline)
            Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
    $ assert position at end of a line

Upvotes: 1

karakfa
karakfa

Reputation: 67467

this should cover both cases

/^\s*\/\*.*/

Upvotes: 1

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