Added 'fetch' command.

cmd/fetch.go

@@ -0,0 +1,55 @@
+// Copyright © 2019 NAME HERE <EMAIL ADDRESS>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"github.com/spf13/cobra"
+)
+
+// fetchCmd represents the fetch command
+var fetchCmd = &cobra.Command{
+	Use:   "fetch [SEARCH]",
+	Short: "Prints the file path of the entry",
+	Long: `Scholar: a CLI Reference Manager
+
+Fetch the file path attached to an entry and print the result to stdout.
+If no file is attached, it exists with 1.
+`,
+	Run: func(cmd *cobra.Command, args []string) {
+		if entry := queryEntry(strings.Join(args, " ")); entry != nil {
+			if entry.File != "" {
+				fmt.Println(filepath.Join(libraryPath(), entry.GetKey(), entry.File))
+			} else if url, ok := entry.Optional["url"]; ok && url != "" {
+				fmt.Println(url)
+			} else if url, ok := entry.Required["url"]; ok && url != "" {
+				fmt.Println(url)
+			} else if doi, ok := entry.Optional["doi"]; ok && doi != "" {
+				fmt.Println(fmt.Sprintf("https://dx.doi.org/%s", doi))
+			} else {
+				panic("no file, doi, or url associated with entry")
+			}
+		} else {
+			panic("entry not found")
+		}
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(fetchCmd)
+}