grep

grep looks like regular expression matches in text, and is a very versatile tool.

Here is the GNU grep manual.

Here are some handy invocations:

• Look for a pattern in a tool's output: adb devices | grep device$
• Look for a fixed string under a directory: grep -RF feedback
• Include or exclude certain files: grep -RF --include '*.md' --exclude '*.html' feedback
• Find patterns but ignore case: grep -R content
• Print only the matching part: adb devices | grep -o '^[a-zA-Z0-9]*'
• Print lines that don't match: ls | grep -v PAT

grep is particularly useful when you stick to plain text.

grep can print out matching file names, but if you need further processing you can turn to something like awk when you want to work on files and print out the per-file results.

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