Bash: find references to filenames in other files - bash

Question

Problem:
I have a list of filenames, filenames.txt:
Eg.
/usr/share/important-library.c
/usr/share/youneedthis-header.h
/lib/delete/this-at-your-peril.c
I need to rename or delete these files and I need to find references to these files in a project directory tree: /home/noob/my-project/ so I can remove or correct them.
My thought is to use bash to extract the filename: basename filename, then grep for it in the project directory using a for loop.
FILELISTING=listing.txt
PROJECTDIR=/home/noob/my-project/
for f in $(cat "$FILELISTING"); do
extension=$(basename ${f##*.})
filename=$(basename ${f%.*})
pattern="$filename"\\."$extension"
grep -r "$pattern" "$PROJECTDIR"
done
I could royally screw up this project -- does anyone see a flaw in my logic; better: do you see a more reliable scalable way to do this over a huge directory tree? Let's assume that revision control is off the table ( it is, in fact ).

Answer 1

A few comments:
Instead of
for f in $(cat "$FILELISTING") ; do
...
done
it's somewhat safer to write
while IFS= read -r f ; do
...
done < "$FILELISTING"
That way, your code will have no problem with spaces, tabs, asterisks, and so on in the filenames (though it still won't support newlines).
Your goal in separating f into extension and filename, and then reassembling them with \., seems to be that you want the filename to be treated as a literal string; right? Like, you're worried that grep will treat the . as meaning "any character" rather than as "one dot". A more general solution is to use grep's -F option, which tells it to treat the pattern as a fixed string rather than a regex:
grep -r -F "$f" "$PROJECTDIR"
Your introduction mentions using basename, but then you don't actually use it. Is that intentional?
If your non-use of basename is intentional, then filenames.txt really just contains a list of patterns to search for; you don't even need to write a loop, in this case, since grep's -f option tells it to take a newline-separated list of patterns from a file:
grep -r -F -f "$FILELISTING" "$PROJECTDIR"
You should back up your project, using something like tar -czf backup.tar.gz "$PROJECTDIR". "Revision control is off the table" doesn't mean you can't have a rollback strategy!
Edited to add:
To pass all your base-names to grep at once, in the hopes that it can do something smarter with them than just looping over them just as though the calls were separate, you can write something like:
grep -r -F "$(sed 's#.*/##g' "$FILELISTING")" "$PROJECTDIR"
(I used sed rather than while+basename for brevity's sake, but you can an entire loop inside the "$(...)" if you prefer.)

Answer 2

This is a job for an IDE.
You're right that this is a perilous task, and unless you know the build process and the search directories and the order of the directories, you really can't say what header is with which file.
Let's take something as simple as this:
# include "sql.h"
You have a file in the project headers/sql.h. Is that file needed? Maybe it is. Maybe not. There's also a /usr/include/sql.h. Maybe that's the one that's actually used. You can't tell without looking at the Makefile and seeing the order of the include directories which is which.
Then, there are the libraries that get included and may need their own header files in order to be able to compile. And, once you get to the C preprocessor, you really will have a hard time.
This is a task for an IDE (Integrated Development Environment). An IDE builds the project and tracks file and other resource dependencies. In the Java world, most people use Eclipse, and there is a C/C++ plugin for those developers. However, there are over 2 dozen listed in Wikipedia and almost all of them are open source. The best one will depend upon your environment.