compress temp files and use bash as default shell

this uses gzip.BestSpeed as the compression level.
This has some CPU cost but BestSpeed is very efficient and
reduces the size of tmp files for my examples by 2-4X.

CHANGES.md

@@ -1,3 +1,8 @@
+0.3.7
+=====
++ compress temporary files with gzip (BestSpeed)
++ default to bash instead of sh if it exists and SHELL is not specified
+
 0.3.6
 =====
 + output gargs version in help.

main.go

@@ -21,7 +21,7 @@ import (
 )
 
 // Version is the current version
-const Version = "0.3.6"
+const Version = "0.3.7"
 
 // ExitCode is the highest exit code seen in any command
 var ExitCode = 0

process/process.go

@@ -3,6 +3,7 @@ package process
 import (
 	"bufio"
 	"bytes"
+	"compress/gzip"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -31,7 +32,11 @@ var prefix = fmt.Sprintf("gargs.%d.", os.Getpid())
 func getShell() string {
 	shell := os.Getenv("SHELL")
 	if shell == "" {
-		shell = "sh"
+		if _, err := os.Stat("/bin/bash"); err == nil {
+			shell = "bash"
+		} else {
+			shell = "sh"
+		}
 	}
 	return shell
 }
@@ -219,15 +224,21 @@ func oneRun(command string, callback CallBack, env []string) *Command {
 	if err != nil {
 		return newCommand(bufio.NewReader(bytes.NewReader(res)), tmp, command, err)
 	}
-	btmp := bufio.NewWriter(tmp)
-	_, err = io.CopyBuffer(btmp, bpipe, res)
+
+	gtmp, err := gzip.NewWriterLevel(tmp, gzip.BestSpeed)
+	if err != nil {
+		return newCommand(bufio.NewReader(bytes.NewReader(res)), tmp, command, err)
+	}
+
+	_, err = io.CopyBuffer(gtmp, bpipe, res)
 	if err != nil {
 		return newCommand(bufio.NewReader(bytes.NewReader(res)), tmp, command, err)
 	}
 	if c, ok := opipe.(io.ReadCloser); ok {
 		c.Close()
 	}
-	btmp.Flush()
+	gtmp.Flush()
+	gtmp.Close()
 	_, err = tmp.Seek(0, 0)
 	if err == nil {
 		err = cmd.Wait()
@@ -237,7 +248,9 @@ func oneRun(command string, callback CallBack, env []string) *Command {
 			err = e
 		}
 	}
-	return newCommand(bufio.NewReader(tmp), tmp, command, err)
+	var grdr *gzip.Reader
+	grdr, err = gzip.NewReader(tmp)
+	return newCommand(bufio.NewReader(grdr), tmp, command, err)
 }
 
 // istring holds a command and an index.