Files for GDB-coreutils dem that illustrate ELF startup

Copying compile_coreutils.sh and gdb-coreutils.txt to the same directory and then executing the script downloads the glibc and coreutils source, compiles coreutils, and illustrates ELF startup with GDB.   Inspired by https://0xax.gitbooks.io/linux-insides/content/Misc/program_startup.html, which is now a bit out of date.

compile_coreutils.sh

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+#!/bin/bash
+#
+set -u
+set -e
+
+if [[ ! -n $(which gcc) || ! -n $(which gdb) ]]; then
+  echo "Install gcc and gdb to proceed."
+  exit 1
+else
+  echo "Found GCC and GDB, proceeding."
+fi
+# This demo would also likely work on derivatives like Mint or Ubuntu.
+if [[ ! -f /etc/debian_version ]]; then
+  echo "Sorry, this is a Debian demo."
+else
+  echo "Confirmed Debian, proceeding."
+fi
+readonly GDBFILE="$(readlink -f gdb-coreutils.txt)"
+if [[ ! -n "$GDBFILE" ]]; then
+  echo "GDB commands file is missing."
+  exit 1
+else
+  echo "Found GDB commands file."
+fi
+
+readonly TESTDIR=./coreutils
+mkdir "$TESTDIR"
+
+# Install glibc sources.
+cd "$TESTDIR"
+echo "Getting glibc source."
+apt-get -q source glibc
+# du -hcs glibc-2.24/
+# 225M    glibc-2.24/
+readonly GLIBCDIR="$(find . -name "glibc*" -type d)"
+
+# Compile coreutils.
+echo "Getting coreutils source."
+apt-get -q source coreutils
+TARBALL="$(ls coreutils*orig.tar.xz)"
+tar xfJ "$TARBALL"
+readonly COREUTILSDIR="$(find . -name "coreutils-*" -type d)"
+
+# Build coreutils.
+cd "$COREUTILSDIR"
+echo "Configuring coreutils"
+# Semicolon matters; 'configure' seems to eat the next line otherwise.
+./configure -q; echo "Compiling coreutils"
+make -s
+
+# Run coreutils under GDB.
+ln -s "$(readlink -f ../"$GLIBCDIR"/sysdeps)" ../sysdeps
+ln -s "$(readlink -f ../"$GLIBCDIR"/csu)" ../csu
+gdb --command="$GDBFILE" src/date

gdb-coreutils.txt

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+# GDB commands to examine the start-up of an ELF binary with glibc.
+# Inspired by https://0xax.gitbooks.io/linux-insides/content/Misc/program_startup.html,
+# which is a bit out-of-date.
+run
+info functions
+b _init
+run
+l 40,100
+# Also interesting:
+# info files
+# Then break at "Entry point":
+# b *(0x????)
+# or, "info address _start"
+