Sed

You need to change a config value across 50 files. You could open each one, or: 1 sed -i 's/old_value/new_value/g' *.conf Done. sed is the stream editor — it transforms text as it flows through. Master it, and you’ll never manually edit repetitive files again. The Basics 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 # Replace first occurrence per line echo "hello hello" | sed 's/hello/hi/' # hi hello # Replace all occurrences (g = global) echo "hello hello" | sed 's/hello/hi/g' # hi hi # Replace in file (print to stdout) sed 's/foo/bar/g' file.txt # Replace in place (-i) sed -i 's/foo/bar/g' file.txt # Backup before in-place edit sed -i.bak 's/foo/bar/g' file.txt The -i flag is powerful and dangerous. Always test without it first. ...

sed (stream editor) processes text line by line, applying transformations as data flows through. It’s the scalpel to awk’s Swiss army knife — focused on text substitution and line manipulation. Basic Substitution 1 2 3 4 5 6 7 8 9 10 11 # Replace first occurrence per line sed 's/old/new/' file.txt # Replace all occurrences per line sed 's/old/new/g' file.txt # Case insensitive sed 's/old/new/gi' file.txt # Replace Nth occurrence sed 's/old/new/2' file.txt # Second occurrence only Delimiters When patterns contain slashes, use different delimiters: ...