Ability to load variable from file - UPDATED

README.md

@@ -32,6 +32,7 @@ applications in an expressive way.
     + [Alternate Names](#alternate-names)
     + [Ordering](#ordering)
     + [Values from the Environment](#values-from-the-environment)
+    + [Values from files](#values-from-files)
     + [Values from alternate input sources (YAML, TOML, and others)](#values-from-alternate-input-sources-yaml-toml-and-others)
     + [Precedence](#precedence)
   * [Subcommands](#subcommands)
@@ -587,6 +588,41 @@ func main() {
 }
 ```
 
+#### Values from files
+
+You can also have the default value set from file via `FilePath`.  e.g.
+
+<!-- {
+  "args": ["&#45;&#45;help"],
+  "output": "password for the mysql database"
+} -->
+``` go
+package main
+
+import (
+  "os"
+
+  "github.com/urfave/cli"
+)
+
+func main() {
+  app := cli.NewApp()
+
+  app.Flags = []cli.Flag {
+    cli.StringFlag{
+      Name: "password, p",
+      Usage: "password for the mysql database",
+      FilePath: "/etc/mysql/password",
+    },
+  }
+
+  app.Run(os.Args)
+}
+```
+
+Note that default values set from file (e.g. `FilePath`) take precedence over
+default values set from the enviornment (e.g. `EnvVar`).
+
 #### Values from alternate input sources (YAML, TOML, and others)
 
 There is a separate package altsrc that adds support for getting flag values

context.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"errors"
 	"flag"
+	"os"
 	"reflect"
 	"strings"
 	"syscall"
@@ -93,18 +94,26 @@ func (c *Context) IsSet(name string) bool {
 					val = val.Elem()
 				}
 
-				envVarValue := val.FieldByName("EnvVar")
-				if !envVarValue.IsValid() {
-					return
+				filePathValue := val.FieldByName("FilePath")
+				if filePathValue.IsValid() {
+					eachName(filePathValue.String(), func(filePath string) {
+						if _, err := os.Stat(filePath); err == nil {
+							c.setFlags[name] = true
+							return
+						}
+					})
 				}
 
-				eachName(envVarValue.String(), func(envVar string) {
-					envVar = strings.TrimSpace(envVar)
-					if _, ok := syscall.Getenv(envVar); ok {
-						c.setFlags[name] = true
-						return
-					}
-				})
+				envVarValue := val.FieldByName("EnvVar")
+				if envVarValue.IsValid() {
+					eachName(envVarValue.String(), func(envVar string) {
+						envVar = strings.TrimSpace(envVar)
+						if _, ok := syscall.Getenv(envVar); ok {
+							c.setFlags[name] = true
+							return
+						}
+					})
+				}
 			})
 		}
 	}