Regex to replace first lowercase character in a line into uppercase

Question

I have a very large file containing thousands of sentences. In all of them, the first word of each sentence begins with lowercase, but I need them to begin with uppercase.

I looked through the site trying to find a regex to do this but I was unable to. I learned a lot about regex in the process, which is always a plus for my job, but I was unable to find specifically what I am looking for.

I tried to find a way of compiling the code from several answers, including the following:

• Convert first lowercase to uppercase and uppercase to lowercase (regex?)
• how to change first two uppercase character to lowercase character on each line in vim
• Regex, two uppercase characters in a string
• Convert a char to upper case using regular expressions (EditPad Pro)

But for different reasons none of them served my purpose.

I am working with a translation-specific application which accepts regex.

Do you think this is possible at all? It would save me hours of tedious work.

Answer 1

You can use this regex to search for the first letters of sentences:

(?<=[\.!?]\s)([a-z])

It matches a lowercase letter [a-z], following the end of a previous sentence (which might end with one of the following: [\.!?]) and a space character \s.

Then make a substitution with \U$1.

It doesn't work only for the very first sentence. I intentionally kept the regex simple, because it's easy to capitalize the very first letter manually.

Working example: https://regex101.com/r/hqwK26/1

UPD: If your software doesn't support \U, you might want to copy your text to Notepad++ and make a replacement there. The \U is fully supported, just checked.

UPD2: According to the comments, the task is slightly different, and just the first letters of each line should be capitalized.

There is a simple regex for that: ^([a-z]), with the same substitution pattern.

Here is a working example: https://regex101.com/r/hqwK26/2

Answer 2

Taking Ildar's answer and combining both of his patterns should work with no compromises. (?<=[\.!?]\s)([a-z])|^([a-z]) This is basically saying, if first pattern OR second pattern. But because you're now technically extracting 2 groups instead of one, you'll have to refer to group 2 as $2. Which should be fine because only one of the patterns should be matched. So your substitution pattern would then be as follows... \U$1$2

Here's a working example, again based on Ildar's answer... https://regex101.com/r/hqwK26/13