Rust command-line library
Common rust command-line macros and utilities, to write shell-script like tasks easily in rust programming language. Available at crates.io.
Why you need this
If you need to run some external commands in rust, the std::process::Command is a good abstraction layer on top of different OS syscalls. It provides fine-grained control over how a new process should be spawned, and it allows you to wait for process to finish and check the exit status or collect all of its output. However, when Redirection or Piping is needed, you need to set up the parent and child IO handles manually, like this in the rust cookbook, which is often a tedious work.
A lot of developers just choose shell(sh, bash, ...) scripts for such tasks, by using <
to redirect input,
>
to redirect output and '|' to pipe outputs. In my experience, this is the only good parts of shell script.
You can find all kinds of pitfalls and mysterious tricks to make other parts of shell script work. As the shell
scripts grow, they will ultimately be unmaintainable and no one wants to touch them any more.
This cmd_lib library is trying to provide the redirection and piping capabilities, and other facilities to make writing shell-script like tasks easily without launching any shell. For the rust cookbook examples, they can usually be implemented as one line of rust macro with the help of this library, as in the examples/rust_cookbook_external.rs. Since they are rust code, you can always rewrite them in rust natively in the future, if necessary without spawning external commands.
What this library provides
Macros to run external commands
-
run_cmd! --> CmdResult
use run_cmd; let msg = "I love rust"; run_cmd!?; run_cmd!?; // pipe commands are also supported run_cmd!?; // or a group of commands // if any command fails, just return Err(...) let file = "/tmp/f"; let keyword = "rust"; if run_cmd! .is_err
-
run_fun! --> FunResult
use run_fun; let version = run_fun!.unwrap; eprintln!; // with pipes let n = run_fun!.unwrap; eprintln!;
Intuitive parameters passing
When passing parameters to run_cmd!
and run_fun!
macros, if they are not part to rust
String literals, they will be
converted to string as an atomic component, so you don't need to quote them. The parameters will be
like $a or ${a} in run_cmd!
or run_fun!
macros.
let dir = "my folder";
run_cmd!?;
run_cmd!?;
// or with group commands:
let dir = "my folder";
run_cmd!?;
You can consider "" as glue, so everything inside the quotes will be treated as a single atomic component.
If they are part of Raw string literals,
there will be no string interpolation, the same as in idiomatic rust. However, you can always use format!
macro
to form the new string. For example:
// string interpolation
let key_word = "time";
let awk_opts = format!;
run_cmd!?;
Redirection and Piping
Right now piping and stdin, stdout, stderr redirections are supported. Most parts are the same as in bash scripts. See examples at examples/redirect.rs
Macros to define, get and set global variables
proc_var!
to define thread local global variableproc_var_get!
to get the valueproc_var_set!
to set the value
use ;
proc_var!;
const DELAY_FACTOR: f64 = 0.8;
proc_var_set!;
let d = proc_var_get!;
// check more examples in examples/tetris.rs
Macros to set scoped process environment variables
proc_env_set!
to define process running related environment variables- Right now, only
PWD
andCMD_LIB_DEBUG
are supported - More variables like GID, UID, UMASK ... are on the way
use ;
proc_env_set!; // to print commands
run_cmd!?;
Builtin commands
cd
cd: set process current directory
run_cmd! ;
Notice that builtin cd
will only change with current scope
and it will restore the previous current directory when it
exits the scope.
Use std::env::set_current_dir
if you want to change the current
working directory for the whole program.
Complete Example
See examples
directory, which contains a tetris game
converted from bash implementation and other simple examples.
Related
See rust-shell-script, which can compile rust-shell-script scripting language directly into rust code.