Comments on How to extract string from file, run filter, and replace in file with new value?
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How to extract string from file, run filter, and replace in file with new value?
TASK
I am coding up ebooks to a specific standard, and have a script that converts a string into the correct titlecase for this publisher. When working with some public domain source files, one often gets this for a chapter title string:
<p>HERE IS MY TITLE</p>
Using VSCodium (FOSS VS Code alternative), I can open each file, select the string between the p tags, then run the titlecase script with a hotkey that I've assigned it to. I end up with
<p>Here Is My Title</p>
(VSCodium's native titlecase filter isn't up to this job.) I save the file, and go on to the next one.
If you only have a few of these to do, that's fine. But sometimes there can be dozens, and it gets very tedious.
QUESTION
Is there a way that I can script this? I have scratched my head over both awk and sed, thinking that these are my prime options. But (as a rank amateur) I cannot work out how to:
- iterate through all
chapter-*.xhtmlfiles in a directory, - extract my string (ALWAYS line 12 in the file, only string on line, between
<p>...</p>tags), -
run my "external"
titlecasefilter on that string, - replace the new string for the original one in the source file,
- for all those files. :)
(The step in bold is the one that is my biggest stumbling block.)
UPDATE: Note that for my titlecase filter, ONLY the string between the tags can be used, so that step #2 (extracting the string) is mandatory. Both the answers so far look very promising, but is it possible to do something like e.g. a regex on sed -n '12p' in one answer?
The other answer suggests using pup although it would be helpful not to need extra packages if a simple regex would do.
UPDATE 2: for "real" data, one could download the ZIP of this commit in a Github repo - the files in question are found at: /src/epub/text/chapter-*.xhtml = the 12th line of every "chapter-nn.xhtml" file.
Post
Both replies, at different points, provided the basis for this working script. Assuming that the 12th line of file has something like:
<p>HERE IS MY TITLE</p>
where HERE... begins at column 8 (I need to omit the opening <p> tag, as noted in the original post), then:
for filename in chapter-*.xhtml; do
new12=$(sed -n '12p' "$filename" | cut -b 8- | se titlecase -n)
sed -i -e '12s#^\(.*<p>\).*#'"\1$new12"'#g' "$filename"
done
The two middle lines work this way:
Line 2:
-
sed -n '12p' "$filename"= print the 12th line of the file -
cut -b 8-= "cut" from the 8th column, so in this example, passing the stringHERE IS MY TITLE</p>to the pipe -
se titlecase -n= run thetitlecasescript (-nprevents it from generating a "newline") - all that assigned to
$new12.
Line 3
-
sed -i -e '12s#^\(.*<p>\).*#'"\1$new12"'#g'= replace original line 12, capturing the first part of the line, up to the opening<p>in a backreference group, so\1in the "replace", combined with the$new12value.
Produces:
<p>Here Is My Title</p>
in "$filename". Done. :)
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