slap
slap (shell clap
) - painless argument parsing and dependency check.
Why?
Writing code to parse arguments in a shell scripting language (bash
, zsh
,
fish
etc...) is an extremly verbose, repetitive, error prone, and painful
process.
This program aims to improve that.
Can't I just use getopt
or something similiar?
getopt
and similiar tools are not only language-dependent (slap works with a number of shells), but are also just tools to write your own argument parser.
slap is different, in the sense that it puts at your disposal an already written argument parser.
Good luck in writing in bash, powershell, fish or whatever, a full fledged argument parser (using getopt
if you want) that takes in consideration things like argument order, possible values, subcommands, argument groups, automatic color-enabled help menus, most similiar argument name suggestions etc.
How?
You declare your CLI in YAML and pass it to slap's stdin
and pass all your
script's arguments to slap as arguments.
slap makes sure that the arguments you pass to it conform to your YAML
description, and if not, it exits with an error code and outputs useful error
messages to stderr
.
In other words slap handles the argument parsing logic and validation, your
script only evalutes the code exported by slap and uses the parsed arguments.
Here is an example bash script:
config="path to your YAML config"
The slap-parse
subcommand, if the passed arguments conform to the YAML
description, outputs code in the language specified, so you can evaluate it to
have access to the variables containing the parsed arguments.
Relax, slap writes to stdout
ONLY if the YAML config is valid and the
arguments passed conform to it, otherwise it doesn't.
Installation
If you're an Arch Linux user, you can install slap from the AUR:
# This will install a binary named `slap`.
If you're a Rust programmer, you can install slap with cargo
.
Make sure to add ~/.cargo/bin
to your $PATH
.
# This will install a binary named `slap`.
You can also download a pre-compiled binary (for linux
, linux-arm
, macos
,
win-msvc
, win-gnu
, win32-msvc
) from the
Releases.
Supported platforms
At the moment slap supports bash
, zsh
, fish
, elvish
and powershell
.
We are planning to support more shells.
If your favourite shell is not supported, make sure to open an issue.
Completions script generation
Thanks to clap, slap's underlying engine, automatic completions-script generation is supported. For example in bash:
config="path to your YAML config"
completions.bash
now contains a bash script that provides command
autocompletion for the CLI described in your YAML config file.
Dependency check
If your script depends on some programs you can check if they are in $PATH
with the deps
subcommand:
||
If curl
and jq
are found in $PATH
the script will continue its execution
and nothing will be printed, otherwise an error will be written to stderr
and
slap will exit with a non-zero exit code.
Absolute path of a script
slap includes a path
subcommand that simplifies getting the absolute path of
a script:
# before
abs=""
# with slap
abs="$(slap path -d "${BASH_SOURCE[0]}")"
Both the snippets never dereference symlinks. If you want to dereference symlinks use the -D
option.
Demo
Example
Here are two useful bash scripts:
||
; &&
page=1
while ; do
data=""
len=""
&& break
&& break
page=""
done
||
; &&
for; do
if ; then
else
fi
done
Learning material
This YAML config probably contains all the
options you'll ever need.
For additional informations look at clap
's
docs.
For powershell
, fish
, zsh
and other
examples look here.
Elvish
As of v0.14.1
, elvish doesn't support eval
yet, so you can use slap to
generate elvish code, but you can't yet use the generated code inside an
elvish script.
Luckily there is some work going on for this functionality.
Credits
This program is solely made possible by clap, so many thanks to its authors.