grep1-8  Exercise 3: Three greps in PowerShell
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(Run in the practice repository from the chapter. Make it first with the block at the top of the chapter, then change into the proj folder.)

Write-Output "Python files with TODO (case-sensitive):"
Get-ChildItem -Recurse -File -Include *.py | Select-String -Pattern TODO -CaseSensitive
Write-Output "lines without TODO in src\db.py:"
Select-String -Path src\db.py -Pattern TODO -NotMatch
Write-Output "files that contain FIXME:"
Get-ChildItem -Recurse -File | Select-String -Pattern FIXME -List | ForEach-Object { Resolve-Path -Relative $_.Path }


Output:

Python files with TODO (case-sensitive):

src\db.py:1:# TODO: use a connection pool
lines without TODO in src\db.py:
src\db.py:2:def connect():
src\db.py:3:    # HACK: retry forever
src\db.py:4:    return None
files that contain FIXME:
.\src\app.js

WHY THIS WORKS AS AN ANSWER
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Get-ChildItem -Recurse -File -Include *.py finds the files (recursion is its job, not Select-String's) and Select-String reads each. -CaseSensitive restores grep's behaviour, which is case-insensitive in PowerShell by default. -NotMatch is grep -v. -List returns only the first match in each file, the nearest thing to grep -l; Resolve-Path -Relative turns the full path into the short one grep would print.
Checking against grep: grep -rn TODO --include='*.py' . finds src/db.py:1, and grep -v TODO src/db.py prints the other three lines, and grep -rl FIXME . prints src/app.js. The answers agree. Remember that Select-String does not read .gitignore and does not skip the build folder, so on a real project add the exclusions yourself (a Where-Object on the path), or use rg or git grep.