initial commit

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "env_or_file"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "env_or_file"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/main.rs

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+#![feature(iter_intersperse)]
+use std::{
+    env,
+    ffi::OsString,
+    fs,
+    os::unix::{
+        ffi::{OsStrExt, OsStringExt},
+        process::CommandExt,
+    },
+    process::Command,
+};
+
+fn main() {
+    let mut child_env = vec![];
+    for (key, value) in env::vars_os() {
+        let key_bytes: Vec<_> = key.as_bytes().into();
+        if key_bytes.ends_with(b"_FILE") && !value.is_empty() {
+            match fs::read(&value) {
+                Ok(content) => {
+                    let key = OsString::from_vec(key_bytes[0..key_bytes.len() - 5].to_owned());
+                    child_env.push((key, OsString::from_vec(content)));
+                }
+                Err(error) => {
+                    panic!(
+                        "failed to read contents of {value:?} (specified by ${}): {error:?}",
+                        key.to_string_lossy()
+                    )
+                }
+            }
+        } else {
+            child_env.push((key, value))
+        }
+    }
+    let mut args = env::args().skip(1);
+    if let Some(cmd) = args.next() {
+        let collected: Vec<_> = args.collect();
+        let mut child = Command::new(&cmd);
+        child.env_clear().envs(child_env);
+        for arg in &collected {
+            child.arg(arg);
+        }
+        let err = child.exec(); // Ideally should not return
+        panic!("error running command {cmd} with args {collected:?}: {err}");
+    } else {
+        panic!("no command given");
+    }
+}