Add -o option to shasum

src/cmd/shasum.rs

@@ -1,10 +1,12 @@
 use std::{
-    fs::File,
+    fs::{File, OpenOptions},
     io::{BufRead, BufReader, Read},
+    path::Path,
 };
 
 use anyhow::{Context, Error, Result};
 use argh::FromArgs;
+use filetime::{set_file_mtime, FileTime};
 use sha1::{Digest, Sha1};
 
 #[derive(FromArgs, PartialEq, Eq, Debug)]
@@ -17,6 +19,9 @@ pub struct Args {
     #[argh(positional)]
     /// path to file
     file: String,
+    #[argh(option, short = 'o')]
+    /// touch output file on successful check
+    output: Option<String>,
 }
 
 const DEFAULT_BUF_SIZE: usize = 8192;
@@ -31,7 +36,7 @@ pub fn run(args: Args) -> Result<()> {
     }
 }
 
-fn check(_args: Args, file: File) -> Result<()> {
+fn check(args: Args, file: File) -> Result<()> {
     let reader = BufReader::new(file);
     let mut mismatches = 0usize;
     for line in reader.lines() {
@@ -63,6 +68,9 @@ fn check(_args: Args, file: File) -> Result<()> {
         eprintln!("WARNING: {} computed checksum did NOT match", mismatches);
         std::process::exit(1);
     }
+    if let Some(out_path) = args.output {
+        touch(&out_path).with_context(|| format!("Failed to touch output file '{}'", out_path))?;
+    }
     Ok(())
 }
 
@@ -86,3 +94,14 @@ fn file_sha1(mut file: File) -> Result<sha1::digest::Output<Sha1>> {
         hasher.update(&buf[0..read]);
     })
 }
+
+fn touch<P: AsRef<Path>>(path: P) -> std::io::Result<()> {
+    if path.as_ref().exists() {
+        set_file_mtime(path, FileTime::now())
+    } else {
+        match OpenOptions::new().create(true).write(true).open(path) {
+            Ok(_) => Ok(()),
+            Err(e) => Err(e),
+        }
+    }
+}