publish environment variables example

examples.txt

@@ -63,7 +63,7 @@ Sorting by Functions
 Line Filters
 # Command-Line Arguments
 # Command-Line Flags
-# Environment Variables
+Environment Variables
 # Spawning Processes
 # Execing Processes
 # Signals

examples/environment-variables/environment-variables.go

@@ -1,24 +1,31 @@
+// [Environment variables](http://en.wikipedia.org/wiki/Environment_variable)
+// are a universal mechanism for [conveying configuration
+// information to Unix programs](http://www.12factor.net/config).
+// Let's look at how to set, get, and list environment variables.
+
 package main
 
-// Use the `os` package to list, set, and get environment
-// variables.
 import "os"
 import "strings"
 import "fmt"
 
 func main() {
-    // `os.Environ` returns a slice of strings in the form
-    // `KEY=value`. You can `strings.Split` them to get
-    // the key and value.
+
+    // To set a key/value pair, use `os.Setenv`. To get a
+    // value for a key, use `os.Getenv`. This will return
+    // an empty string if the key isn't present in the
+    // environment.
+    os.Setenv("FOO", "1")
+    fmt.Println("FOO:", os.Getenv("FOO"))
+    fmt.Println("BAR:", os.Getenv("BAR"))
+
+    // Use `os.Environ` to list all key/value pairs in the
+    // environment. This returns a slice of strings in the
+    // form `KEY=value`. You can `strings.Split` them to
+    // get the key and value. Here we print all the keys.
+    fmt.Println()
     for _, e := range os.Environ() {
         pair := strings.Split(e, "=")
         fmt.Println(pair[0])
     }
-    fmt.Println()
-
-    // `Setenv` sets a given key, value pair.
-    // `Getenv` returns the value at key, or an empty
-    // string if the key isn't present.
-    os.Setenv("FOO", "bar")
-    fmt.Println(os.Getenv("FOO"))
 }

examples/environment-variables/environment-variables.sh

@@ -1,6 +1,19 @@
+# Running the program shows that we pick up the value
+# value for `FOO` that we set in the program.
 $ go run environment-variables.go
-HOME
+FOO: 1
+BAR: 
+
+# The list of keys in the environment will depend on your
+# particular machine.
+TERM_PROGRAM
 PATH
-PWD
+SHELL
+...
+
+# If we set `BAR` in the environemnt first, the running
+# program picks that value up.
+$ BAR=2 go run environment-variables.go
+FOO: 1
+BAR: 2
 ...
-bar

tools/measure.go

@@ -21,7 +21,7 @@ func readLines(path string) []string {
     return strings.Split(string(srcBytes), "\n")
 }
 
-var todoPat = regexp.MustCompile("\\/\\/ todo: ")
+var commentPat = regexp.MustCompile("\\s*\\/\\/")
 
 func main() {
     sourcePaths, err := filepath.Glob("./examples/*/*")
@@ -31,7 +31,7 @@ func main() {
         foundLongLine := false
         lines := readLines(sourcePath)
         for i, line := range lines {
-            if !foundLongLine && !todoPat.MatchString(line) && (len(line) > 58) {
+            if !foundLongLine && !commentPat.MatchString(line) && (len(line) > 58) {
                 fmt.Printf("measure: %s:%d\n", sourcePath, i+1)
                 foundLongLine = true
                 foundLongFile = true