commit e523a510e1188dd0314475df85d148b7e33224e5
Author: stephen mcquay <stephen@mcquay.me>
Date:   Tue Dec 8 10:18:42 2015 -0800

    init

diff --git a/license b/license
new file mode 100644
index 0000000..68bbb1b
--- /dev/null
+++ b/license
@@ -0,0 +1,20 @@
+MIT License
+Copyright (c) 2015 smcquay
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..9869453
--- /dev/null
+++ b/main.go
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+package main
+
+import (
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+)
+
+var algo = flag.String("a", "sha256", "algorithm to use")
+
+func main() {
+	flag.Parse()
+	files := flag.Args()
+	h := sha256.New()
+	switch *algo {
+	case "sha1", "1":
+		h = sha1.New()
+	case "sha256", "256":
+		h = sha256.New()
+	case "sha512", "512":
+		h = sha512.New()
+	default:
+		fmt.Fprintf(os.Stderr, "unsupported algorithm: %v\n", *algo)
+		os.Exit(1)
+	}
+
+	if len(files) == 0 {
+		_, err := io.Copy(h, os.Stdin)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", err)
+			os.Exit(1)
+		}
+		fmt.Printf("%x  -\n", h.Sum(nil))
+	} else {
+		for _, name := range files {
+			f, err := os.Open(name)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "%v\n", err)
+				continue
+			}
+			h.Reset()
+			_, err = io.Copy(h, f)
+			f.Close()
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "%v\n", err)
+				continue
+			}
+			fmt.Printf("%x  %s\n", h.Sum(nil), name)
+		}
+	}
+}
diff --git a/readme.md b/readme.md
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+++ b/readme.md
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+# cs
+
+calculate checksums
+
+It's a simpler version of shasum + md5sum, but only for sha1, sha256, and
+sha512.
+
+## usage
+
+    cs -a 256 < foo.txt
+    cs foo.txt
+    cs -a sha1 foo.txt foo.txt foo.txt