2 releases
0.1.1 | Feb 16, 2019 |
---|---|
0.1.0 | Feb 16, 2019 |
#139 in #env-var
154 downloads per month
Used in 8 crates
(2 directly)
30KB
574 lines
Overview
This is a rust attribute-like proc macro which reduces the amount of code required to call shell commands and parse the results.
It allows you to wrap a script in any language with strongly typed functions. The function's arguments are set as env variables and the result of the script is parsed either as a value or as an iterator.
Examples
Basic
use shellfn::shell;
use std::error::Error;
#[shell]
fn list_modified(dir: &str) -> Result<impl Iterator<Item=String>, Box<Error>> { r#"
cd $DIR
git status | grep '^\s*modified:' | awk '{print $2}'
"# }
Different interpreter
use shellfn::shell;
use std::error::Error;
#[shell(cmd = "python -c")]
fn pretty_json(json: &str, indent: u8, sort_keys: bool) -> Result<String, Box<Error>> { r#"
import os, json
input = os.environ['JSON']
indent = int(os.environ['INDENT'])
sort_keys = os.environ['SORT_KEYS'] == 'true'
obj = json.loads(input)
print(json.dumps(obj, indent=indent, sort_keys=sort_keys))
"# }
Usage
You can use the #[shell]
attribute on functions that have:
- a body containing only one expression - a string literal representing the script to execute
- types that implement the
.to_string()
method - return a value that is either
void
,T
,Result<T, E>
,impl Iterator<Item=T>
,Result<impl Iterator<Item=T>>
orResult<impl Iterator<Item=Result<T, E>>>
with constrains:
T: FromStr,
<T as FromStr>::Err: StdError,
E: From<shellfn::Error<<T as FromStr>::Err>>,
-
Details
The #[shell]
attribute does the following:
- Sets every argument as an env variable
- Runs a shell command
- Launches the command using
std::process::Command
- Depending on the return type, it may parse the output
Most of the steps can be adjusted:
- the default command is
bash -c
. You can change it using thecmd
parameter:
#[shell(cmd = "python -c")]
- by default, the script is added as the last argument. You can change it using the special variable
PROGRAM
in thecmd
parameter:
#[shell(cmd = "bash -c PROGRAM -i")]
- you can use env variables set from function's arguments in the
cmd
parameters in the same way as in the script:
#[shell(cmd = "python -m $MODULE")]
fn run(module: &str)
- if the return type is not wrapping some part of the result in
Result
, you may decide to suppress panics by adding theno_panic
flag:
#[shell(no_panic)]
Following return types are currently recognized:
return type | flags | on parse fail | on error exit code | on spawn fail | notes |
---|---|---|---|---|---|
- | panic | panic | |||
no_panic | - | nothing | nothing | ||
() | - | panic | panic | ||
() | no_panic | - | nothing | nothing | |
Result<(), E> | - | error | error | ||
Result<(), E> | no_panic | - | error | error | 1 |
T | panic | panic | panic | 2 | |
T | no_panic | panic | panic | panic | 1,2 |
Result<T, E> | error | error | error | 2 | |
Result<T, E> | no_panic | error | error | error | 1,2 |
Vec | panic | panic | panic | ||
Vec | no_panic | skip | ignored | empty vec | 3 |
Vec<Result<T, E>> | item error | panic | panic | ||
Vec<Result<T, E>> | no_panic | item error | ignored | empty vec | |
Result<Vec, E> | panic | error | error | ||
Result<Vec, E> | no_panic | skip | error | error | |
Result<Vec<Result<T, E1>>, E2> | item error | error | error | ||
Result<Vec<Result<T, E1>>, E2> | no_panic | item error | error | error | 1 |
impl Iterator<Item=T> | panic | panic | panic | ||
impl Iterator<Item=T> | no_panic | skip | ignored | empty iter | 3 |
impl Iterator<Item=Result<T, E>> | item error | panic | panic | 3 | |
impl Iterator<Item=Result<T, E>> | no_panic | item error | ignored | empty iter | |
Result<impl Iterator<Item=T>, E> | panic | ignored | error | ||
Result<impl Iterator<Item=T>, E> | no_panic | skip | ignored | error | |
Result<impl Iterator<Item=Result<T, E1>>, E2> | item error | ignored | error | ||
Result<impl Iterator<Item=Result<T, E1>>, E2> | no_panic | item error | ignored | error | 1 |
Glossary:
action | meaning |
---|---|
panic | panics (.expect or panic!) |
nothing | consumes and ignores error (let _ = ...) |
error | returns error |
skip | yields all successfuly parsed items, ignores parsing failures (filter_map) |
empty iter/vec | returns empty iterator / vector |
item error | when parsing fails, yields Err |
ignored | ignores exit code, behaves in the same way for exit code 0 and != 0 |
Notes:
- The
no_panic
attribute makes no difference - It reads all of stdout before producing any failures
- It yields all items until it encounters an error or an exit code
Vector vs iterator
Variants with the Vec
return type are very similar to the ones with impl Iterator
. The key differences are:
impl Iterator
is only allocating one item at the time and yields it immediately after it is parsed, whileVec
is reading output line by line but stores parsed output in the temporary VecVec
is aware of exit code. When subprocess finishes with error,impl Iterator
will stop yielding values whileVec
will return error or panic
Contribution
All contributions and comments are more than welcome! Don't be afraid to open an issue or PR whenever you find a bug or have an idea to improve this crate.
License
MIT License
Copyright (c) 2017 Marcin Sas-Szymański
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Dependencies
~460KB