Don Johnson copyleftdev

linux-archaeology

Reason through shell pipeline problems and surface the right forgotten Linux command. Each section maps a real situation to a specific tool with concrete invocations.

TRIGGER

Invoke this skill when the user:

Wants to monitor a running process, file, or resource without modifying the process
Needs to send output to both the screen and a file at the same time

	# WASM image — compiled to WASI preview1 target (Go 1.21+).
	# The resulting container holds a single .wasm binary on a scratch base.
	# Run via Docker+Wasm (experimental) or directly with wasmtime/wasmedge.
	# Build (from repo root): docker build -f runtimes/wasm/Dockerfile -t micro-containers-wasm .

	FROM golang:1.24 AS builder
	WORKDIR /src
	COPY go.mod ./
	RUN go mod download
	COPY cmd/wasm/ ./cmd/wasm/

	# OCI image — works with runc, gVisor (runsc), Kata (QEMU), and Kata (Firecracker).
	# The runtime is injected via RUNTIME_NAME at `docker run` time.
	# Build: docker build -t micro-containers .

	FROM golang:1.24-alpine AS builder
	WORKDIR /src
	COPY go.mod ./
	RUN go mod download
	COPY cmd/server/ ./cmd/server/
	RUN CGO_ENABLED=0 GOOS=linux go build \

	// WASI preview1 target — compiled with GOOS=wasip1 GOARCH=wasm.
	// net/http is not available in wasip1; this demonstrates env access,
	// stdout, and runtime introspection inside a WASM container.
	// The wasi-http proposal (https://github.com/WebAssembly/wasi-http)
	// will bring full HTTP support to WASI in a future Go release.
	package main

	import (
	"encoding/json"
	"fmt"

	package main

	import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"runtime"
	"time"
	)

	# parallel — GNU parallel: xargs -P with sane defaults
	# sudo apt install parallel

	# Basic concurrent execution:
	cat tasks.txt \| parallel <command> {}
	ls *.sh \| parallel bash {}

	# Control concurrency:
	cat tasks.txt \| parallel -j4 <command> {} # max 4 jobs
	cat tasks.txt \| parallel -j0 <command> {} # one per CPU core

	# vidir — edit a directory listing in $EDITOR (from moreutils)
	# sudo apt install moreutils

	vidir directory/ # open all files in editor
	ls *.sh \| vidir - # open a specific subset

	# In your editor:
	# - Edit a path → renames the file
	# - Delete a line → deletes the file
	# - Change directory prefix → moves the file

	# tac — cat backwards: last line first
	# (tac is cat spelled backwards)

	tac logfile.log # reverse entire file
	tac logfile.log \| head -20 # last 20 lines, newest-first
	tac logfile.log \| grep -m1 'ERROR' # last occurrence of ERROR

	# Process a JSONL file newest-first:
	tac data.jsonl \| head -5 \| python3 -c "
	import sys, json

	# comm — line-by-line comparison of two sorted files
	# Input must be sorted. Use: sort file \| sponge file

	comm a.txt b.txt # 3 columns: only-A \| only-B \| both

	comm -23 a.txt b.txt # only in A (suppress cols 2 and 3)
	comm -13 a.txt b.txt # only in B (suppress cols 1 and 3)
	comm -12 a.txt b.txt # in both (suppress cols 1 and 2)

	# Sort on the fly with process substitution:

	# column — align delimited input into a readable table

	# TSV file:
	column -t -s $'\t' models.tsv

	# CSV:
	column -t -s ',' data.csv

	# Colon-separated:
	column -t -s ':' /etc/passwd