ion1-mischacks

= MiscHacks

• http://johan.kiviniemi.name/software/mischacks/

== DESCRIPTION:

Miscellaneous methods that may or may not be useful.

sh:: Safely pass untrusted parameters to sh scripts.

fork_and_check:: Run a block in a forked process and raise an exception if the process returns a non-zero value.

do_and_exit, do_and_exit!:: Run a block. If the block does not run exit!, a successful exec or equivalent, run exit(1) or exit!(1) ourselves. Useful to make sure a forked block either runs a successful exec or dies.

Any exceptions from the block are printed to standard error.

overwrite:: Safely replace a file. Writes to a temporary file and then moves it over the old file.

tempname_for:: Generates an unique temporary path based on a filename. The generated filename resides in the same directory as the original one.

try_n_times:: Retries a block of code until it succeeds or a maximum number of attempts (default 10) is exceeded.

Exception#to_formatted_string:: Returns a string that looks like how Ruby would dump an uncaught exception.

IO#best_datasync:: Tries fdatasync, falling back to fsync, falling back to flush.

== FEATURES/PROBLEMS:

The sh method is only safe if your sh script is safe. If unsure, add double quotation marks around all variable references ("$1", "$foo", "$@"), and never, ever use an untrusted variable as a command.

== SYNOPSIS:

sh

MiscHacks.sh %q{ diff -u "$1" "$2" | tr a-z A-Z >"$output" }, '/dev/null', '/etc/motd', :output => 'foo'

unsafe_str = %q{" 'foo' $(bar) baz "} MiscHacks.sh 'printf "%s\n" "$1"', unsafe_str

fork_and_check

These examples raise MiscHacks::ChildError.

MiscHacks.fork_and_check do exit! 42 end MiscHacks.fork_and_check do exec 'sh', '-c', 'exit 42' end MiscHacks.fork_and_check do exec 'failure' end

Does not raise an error.

MiscHacks.fork_and_check do exit! 0 end

do_and_exit

Prints foo if there are no failures. If anything fails, raises an

exception.

MiscHacks.fork_and_check do MiscHacks.do_and_exit! do exec 'sh', '-c', 'echo foo' end end

overwrite

MiscHacks.overwrite 'myconfig' do |io| io << config.to_yaml end

tempname_for

MiscHacks.tempname_for '/foo/bar/baz' # => '/foo/bar/.baz.klyce3f517qkh9l'

try_n_times

io = MiscHacks.try_n_times do File.open path, File::RDWR|File::CREAT|File::EXCL end

== REQUIREMENTS:

• POSIX sh
• A system that implements fork

== INSTALL:

• sudo gem install ion1-mischacks --source http://gems.github.com/

== LICENSE:

Copyright © 2009 Johan Kiviniemi

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.