This is an attempt at recreating the functionality of GNU Parallel in Rust under a MIT license. The end goal will be to support much of the functionality of GNU Parallel and then to extend the functionality further for the next generation of command-line utilities written in Rust.
Here are some benchmarks from an i5-2410M laptop running Gentoo.
sh
time parallel 'echo {#}: {}' ::: /usr/bin/* > /dev/null
real 0m5.728s
user 0m2.960s
sys 0m1.310s
--ungroup Option
real 0m4.801s
user 0m2.070s
sys 0m1.290s
sh
time target/release/parallel 'echo {#}: {}' ::: /usr/bin/* > /dev/null
The default options are the slowest options, with all features enabled.
real 0m1.198s
user 0m0.130s
sys 0m0.550s
--no-shell optionsh
time target/release/parallel --no-shell 'echo {#}: {}' ::: /usr/bin/* > /dev/null
A significant amount of overhead is caused by executing commands within the platform's preferred shell. On Unix
systems, that shell is sh, whereas on Windows it is cmd. Disabling shell executing is a good idea if your
command is simple and doesn't require chaining multiple commands.
real 0m0.559s
user 0m0.084s
sys 0m0.372s
--no-shell and --ungroup Optionsh
time target/release/parallel --no-shell --ungroup 'echo {#}: {}' ::: /usr/bin/* > /dev/null
This will achieve utmost optimization at the cost of not having the standard output and error printed in order.
``` real 0m0.575s user 0m0.060s sys 0m0.450s
```
The following syntax is supported:
sh
parallel 'echo {}' ::: * // {} will be replaced with each input found.
parallel echo ::: * // If no placeholders are used, it is automatically assumed.
parallel echo :::: list1 list2 list3 // Read newline-delimited arguments stored in files.
parallel echo ::: arg1 :::: list ::: arg2 // Interchangeably read arguments from the command line and files.
parallel ::: "echo 1" "echo 2" "echo 3" // If no command is supplied, the input arguments become commands.
parallel 'cd {}; echo Directory: {}; echo - {}' // Commands may be chained in the platform\'s shell.
ls | parallel 'echo {}' // If no input arguments are supplied, stdin will be read.
Parallel parallelizes otherwise non-parallel command-line tasks. When there are a number of commands that need to be executed, which may be executed in parallel, the Parallel application will evenly distribute tasks to all available CPU cores. There are three basic methods for how commands are supplied:
A COMMAND may be defined, followed by an which denotes that all following arguments will be usde as INPUTS for the command.
If no COMMAND is provided, then the INPUTS will be interpreted as COMMANDS.
If no INPUTS are provided, then standard input will be read for INPUTS.
By default, Parallel groups the standard output and error of each child
process so that outputs are printed in the order that they are given, as
if the tasks were executed serially in a traditional for loop. In addition,
commands are executed in the platform's preferred shell by default, which
is sh -c on Unix systems, and cmd /C on Windows. These both come at a
performance cost, so they can be disabled with the --ungroup and --no-shell
options.
Input modes are used to determine whether the following inputs are files that contain inputs or inputs themselves. Files with inputs have each input stored on a separate line, and each line is considered an entire input.
::: Denotes that the input arguments that follow are input arguments.
:::: Denotes that the input arguments that follow are files with inputs.
COMMANDs are typically formed the same way that you would normally in the shell, only that you will replace your input arguments with placeholder tokens like {}, {.}, {/}, {//} and {/.}. If no tokens are provided, it is inferred that the final argument in the command will be {}. These tokens will perform text manipulation on the inputs to mangle them in the way you like. Ideas for more tokens are welcome.
Options may also be supplied to the program to change how the program operates:
less).ffmpeg is a highly useful application for converting music and videos. However, audio transcoding is limited to a a single core. If you have a large FLAC archive and you wanted to compress it into the efficient Opus codec, it would take forever with the fastest processor to complete, unless you were to take advantage of all cores in your CPU.
sh
parallel 'ffmpeg -v 0 -i "{}" -c:a libopus -b:a 128k "{.}.opus"' ::: $(find -type f -name '*.flac')
VP9 has one glaring flaw in regards to encoding: it can only use about three cores at any given point in time. If you have an eight core processor and a dozen or more episodes of a TV series to transcode, you can use the parallel program to run three jobs at the same time, provided you also have enough memory for that.
sh
vp9_params="-c:v libvpx-vp9 -tile-columns 6 -frame-parallel 1 -rc_lookahead 25 -threads 4 -speed 1 -b:v 0 -crf 18"
opus_params="-c:a libopus -b:a 128k"
parallel -j 3 'ffmpeg -v 0 -i "{}" $vp9_params $opus_params -f webm "{.}.webm"' ::: $(find -type f -name '*.mkv')
There are a number of methods that you can use to install the application. I provide binary packages for AMD64 systems that are available for download:
I have a personal Gentoo layman overlay that provides this application for installation.
Debian packages are provided on the releases page. If a release is not available, it's because I haven't built it yet with cargo deb.
sh
wget https://github.com/mmstick/parallel/releases/download/0.2.3/parallel_0.2.3_amd64.tar.xz
tar xf parallel_0.2.3.tar.xz
sudo install parallel /usr/local/bin
All of the dependencies are vendored locally, so it is possible to build the packages without Internet access.
If you would like to install the latest release directly to ~/.cargo/bin using the official method.
sh
cargo install parallel
If you would like to install the latest git release:
sh
cargo install --git https://github.com/mmstick/parallel parallel
If you would like to install it system-wide.
sh
wget https://github.com/mmstick/parallel/archive/master.zip
unzip master.zip
cd parallel-master
cargo build --release
sudo install target/release/parallel /usr/local/bin