Add a function to call commands with str as input and return the output as String.

src/main.rs

@@ -7,6 +7,7 @@ mod password;
 mod repl;
 mod skey;
 mod structs;
+mod utils;
 
 use rpassword::prompt_password;
 use rustyline::Editor;

src/utils.rs

@@ -0,0 +1,16 @@
+use std::io;
+use std::io::{Read, Write};
+use std::process::{Command, Stdio};
+
+pub fn call_cmd_with_input(cmd: &str, args: Vec<&str>, input: &str) -> io::Result<String> {
+    let mut cmd = Command::new(cmd).args(args).stdin(Stdio::piped()).stdout(Stdio::piped()).spawn()?;
+    let stdin = cmd.stdin.as_mut().unwrap();
+    stdin.write_all(input.as_bytes())?;
+    let stdout = cmd.stdout.as_mut().unwrap();
+    let mut output = Vec::new();
+    stdout.read_to_end(&mut output)?;
+    match String::from_utf8(output) {
+        Ok(x) => Ok(x),
+        Err(err) => Err(io::Error::new(io::ErrorKind::InvalidData, err.utf8_error())),
+    }
+}