Pipes, grep, sed and awk

The shell's real power is joining small tools with pipes. A pipe, the | character, sends the output of one command into the next. grep finds lines that match a pattern.

sort puts lines in order and uniq -c counts repeats. cut and awk pull out columns, and sed edits text as it flows past. Redirection with > and >> saves results to a file.

Together they answer questions like "which ten IP addresses made the most requests?" in one line: awk '{print $1}' access.log | sort | uniq -c | sort -rn | head. This is how you dig through logs on a server before any dashboard exists. It is also the heart of most Bash scripts.