Crate ubend

Expand description

U-Bend

This is a small crate that lets you build pipe chains between spawned processes using a syntax similar to the Unix shell.

 
let output = ubend!(
		cat <"./tests/input.txt" |
		grep "spam" |
		wc "-l"
	).expect("spawn failed").
	output().
	expect("reading output failed").
	stdout;
 
let output = String::from_utf8(output).
	expect("UTF-8 error").
	trim().
	parse::<i64>().
	unwrap();
 
println!("output: {}", output);

Note that arguments to commands need always to be quoted. If you don’t quote them they are interpreted as Rust identifiers which allows you to pass dynamic strings. Also FOO="bar" cat <"baz" is the same as FOO = "bar" cat < "baz", since whitespace is ignored in Rust.

use ubend::IntoPipeSetup is needed when passing a file name or std::fs::File as redirection source/target.

Note: Currently only Linux ist tested. Other Unix operating systems might work, too. Windows support is not implemented.

More Examples

use ubend::PipeSetup::*;
 
// Ignore stderr
ubend!(rm "no_such_file" 2>Null);
 
// Redirect stderr to stdout
ubend!(rm "no_such_file" 2>&1);
 
// Write stderr to stderr of this process
ubend!(rm "no_such_file" 2>Inherit);
 
// Read from a file opened in Rust
let file = File::open("./tests/input.txt").
	expect("couldn't open file");
ubend!(grep "spam" <file);
 
// Write stderr to a temp file
let mut chain = ubend!(rm "no_such_file" 2>Temp).
	expect("spawn failed");
 
chain.wait_last().
	expect("wait failed");
 
let mut temp = chain.stderr().unwrap();
 
// Since the file descriptor was shared with the spawned process the
// position needs to be reset manually:
temp.seek(SeekFrom::Start(0)).
	expect("seek failed");