added

vendor/github.com/glycerine/zygomys/zygo/system.go

@@ -0,0 +1,125 @@
+package zygo
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+)
+
+var ShellCmd string = "/bin/bash"
+
+func init() {
+	SetShellCmd()
+}
+
+// set ShellCmd as used by SystemFunction
+func SetShellCmd() {
+	if runtime.GOOS == "windows" {
+		ShellCmd = os.Getenv("COMSPEC")
+		return
+	}
+	try := []string{"/usr/bin/bash"}
+	if !FileExists(ShellCmd) {
+		for i := range try {
+			b := try[i]
+			if FileExists(b) {
+				ShellCmd = b
+				return
+			}
+		}
+	}
+}
+
+// sys is a builder. shell out, return the combined output.
+func SystemBuilder(env *Zlisp, name string, args []Sexp) (Sexp, error) {
+	//P("SystemBuilder called with args='%#v'", args)
+	return SystemFunction(env, name, args)
+}
+
+func SystemFunction(env *Zlisp, name string, args []Sexp) (Sexp, error) {
+	if len(args) == 0 {
+		return SexpNull, WrongNargs
+	}
+
+	flat, err := flattenToWordsHelper(args)
+	if err != nil {
+		return SexpNull, fmt.Errorf("flatten on '%#v' failed with error '%s'", args, err)
+	}
+	if len(flat) == 0 {
+		return SexpNull, WrongNargs
+	}
+
+	joined := strings.Join(flat, " ")
+	cmd := ShellCmd
+
+	var out []byte
+	if runtime.GOOS == "windows" {
+		out, err = exec.Command(cmd, "/c", joined).CombinedOutput()
+	} else {
+		out, err = exec.Command(cmd, "-c", joined).CombinedOutput()
+	}
+	if err != nil {
+		return SexpNull, fmt.Errorf("error from command: '%s'. Output:'%s'", err, string(Chomp(out)))
+	}
+	return &SexpStr{S: string(Chomp(out))}, nil
+}
+
+// given strings/lists of strings with possible whitespace
+// flatten out to a array of SexpStr with no internal whitespace,
+// suitable for passing along to (system) / exec.Command()
+func FlattenToWordsFunction(env *Zlisp, name string, args []Sexp) (Sexp, error) {
+	if len(args) == 0 {
+		return SexpNull, WrongNargs
+	}
+	stringArgs, err := flattenToWordsHelper(args)
+	if err != nil {
+		return SexpNull, err
+	}
+
+	// Now convert to []Sexp{SexpStr}
+	res := make([]Sexp, len(stringArgs))
+	for i := range stringArgs {
+		res[i] = &SexpStr{S: stringArgs[i]}
+	}
+	return env.NewSexpArray(res), nil
+}
+
+func flattenToWordsHelper(args []Sexp) ([]string, error) {
+	stringArgs := []string{}
+
+	for i := range args {
+		switch c := args[i].(type) {
+		case *SexpStr:
+			many := strings.Split(c.S, " ")
+			stringArgs = append(stringArgs, many...)
+		case *SexpSymbol:
+			stringArgs = append(stringArgs, c.name)
+		case *SexpPair:
+			carry, err := ListToArray(c)
+			if err != nil {
+				return []string{}, fmt.Errorf("tried to convert list of strings to array but failed with error '%s'. Input was type %T / val = '%#v'", err, c, c)
+			}
+			moreWords, err := flattenToWordsHelper(carry)
+			if err != nil {
+				return []string{}, err
+			}
+			stringArgs = append(stringArgs, moreWords...)
+		default:
+			return []string{}, fmt.Errorf("arguments to system must be strings; instead we have %T / val = '%#v'", c, c)
+		}
+	} // end i over args
+	// INVAR: stringArgs has our flattened list.
+	return stringArgs, nil
+}
+
+func Chomp(by []byte) []byte {
+	if len(by) > 0 {
+		n := len(by)
+		if by[n-1] == '\n' {
+			return by[:n-1]
+		}
+	}
+	return by
+}