#!/usr/bin/perl
# -*- mode: cperl; coding: utf-8; -*-

use strict;
use warnings;
use utf8;

use lib "/h/hamren/src/post/lib", "."; my $rval = do "common.pm" || die "$0: common.pm failed ($!) [$@]";  #--- Single-line common initializer

#--- End of header

post(
     header(),
     p("When downloading, compiling and installing applications from source, the installed programs ususally end up in ",
       tt("/usr/local/bin"),
       ", ",
       tt("/usr/local/share"),
       ", ",
       tt("/usr/local/lib"),
       " and other subdirectories of ",
       tt("/usr/local"),
       ". After a while ",
       tt("/usr/local"),
       " becomes messy. It is difficult to know which files belong to which package, and removing a package becomes a chore. Many packages have some kind of support for uninstalling (e.g. ",
       tt("make uninstall"),
       "), but not all."),

     p("There is a simple way of solving this problem. Instead of installing all packages to ", tt("/usr/local"), ", install each package to its own subdirectory of ", tt("/usr/local"), ", then symlink it to ", tt("/usr/local/bin"), " &c. A package can then be removed by a) removing its own unique subdirectory, and b) removing all dangling symbolic links."),

     p("If the source is in ", tt("/usr/local/src/gcc-5.3.0"), ", then put the resulting program in ", tt("/usr/local/prog/gcc-5.3.0"), ". This example assumes GNU configure:"),

source_codeq(<<'EOF'),
	$ cd /usr/local/src/gcc-5.3.0
	$ ./configure --prefix=$(/bin/pwd | sed -e 's/src/prog/')
	$ make && make install
EOF

     p("Then install into the regular places using symbolic links. GNU ",
       tt("cp"), " has an option ",
       tt("-s"), " for doing just that. Here is a script to automate installation:"),

source_codeq(<<'END'),
	#!/bin/bash -e

	usage() {
	    echo "Usage: $(basename $0) source-dirs... target-dir" 1&>2
	    exit 1
	}

	[ $# -gt 1 ] || { usage $0; }

	DESTDIR="${@: -1}"

	[ -d $DESTDIR/. ] || {
	    echo "$0: Target directory $DESTDIR does not exist" 1&>2;
	    exit 1;
	}),

	echo mkdir -p $DESTDIR/share

	for i in "${@:1:$(($#-1))}"
	do
	    for d in bin etc include info lib man share/man; do
	        if [ -d $i/$d ] ; then
	           D=$(readlink -e $DESTDIR/`dirname $d`/.)
	           echo cp -sfrv $i/$d $D/.
	        fi
	    done
	done
END

     p("The odd-looking assignment ",
      tt(q<DESTDIR="${@: -1}">), " extracts the very last argument on the command line. The even odder-looking for statement ",
      tt(q<for i in "${@:1:$(($#-1))}">), " loops over all but the last argument. This makes the script behave as ",
      tt("cp"), " and ",
      tt("mv"), ", which take one or more source arguments, and a target argument at the end."),

    p("The script writes command to stdout."),

source_codeq(<<'END'),
	linkin.sh /usr/local/prog/gcc-5.3.0 /usr/local
	mkdir -p /usr/local/share,
	cp -sfrv /usr/local/prog/gcc-5.3.0/bin /usr/local/.
	cp -sfrv /usr/local/prog/gcc-5.3.0/include /usr/local/.
	cp -sfrv /usr/local/prog/gcc-5.3.0/lib /usr/local/.
	cp -sfrv /usr/local/prog/gcc-5.3.0/share/man /usr/local/share/.
END

    p("To execute the commands, pipe to ",
      tt("sh"), ". Then convert absolute links to relative links:"),

source_codeq(<<'END'),
	#!/bin/bash -e
	p("cd /usr/local"),

	#
	# -r: Recursive
	# -c: Convert absolute links to relative links
	# -d: Remove dangling links
	# -s: Detect lengthy links
	#
	symlinks -rcds bin etc include info lib man share \> /dev/null})
END


    p("Call this script ",
      tt("clean-usr-local.sh"),
      ". To uninstall:"),

source_codeq(<<'END'),
	$ rm -rf /usr/local/prog/gcc-5.3.0
	$ clean-usr-local.sh
END

    p("That is all that is needed to get full control of /usr/local, but to go one step further, I have a script that:"),

    ul(
       q<Deletes the "target" subdirectories of > . tt("/usr/local") . ", like " . tt("bin") . " and " . tt("share") . ".",
       "Reinstalls the symbolic links for the packages I want.",
       "Performs additional installation, like updating " . tt("/etc/ld.so.conf.d/") . "."),

    p("Warning! Be really, really careful when experimenting with things like this. A single bad ",
      tt("sudo rm -r"),
      " can completely destroy your file system. That is why I often print commands to stdout, instead of executing them. You have been warned."),

    footer()
);