Add README

1 files changed, 114 insertions, 0 deletions

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..34fd70c
--- /dev/null
+++ b/README.md
@@ -0,0 +1,114 @@
+## Description
+
+pflag is a drop-in replacement for Go's flag package, implementing
+POSIX/GNU-style --flags.
+
+pflag is compatible with the GNU extensions to the POSIX recommendations
+for command-line options. See
+http://www.gnu.org/software/libc/manual/html_node/Argument-Syntax.html
+
+pflag is available under the same style of BSD license as the Go language,
+which can be found in the LICENSE file.
+
+## Installation
+
+pflag is available using the standard `go get` command.
+
+Install by running:
+    go get github.com/ogier/pflag
+
+Run tests by running:
+    go test github.com/ogier/pflag
+
+## Usage
+
+pflag is a drop-in replacement of Go's native flag package. If you import
+pflag under the name "flag" then all code should continue to function
+with no changes.
+
+    import flag "github.com/ogier/pflag"
+
+There is one exception to this: if you directly instantiate the Flag struct
+there is one more field "Shorthand" that you will need to set.
+Most code never instantiates this struct directly, and instead uses
+functions such as String(), BoolVar(), and Var(), and is therefore
+unaffected.
+
+Define flags using flag.String(), Bool(), Int(), etc. Example:
+    var ip *int = flag.Int("flagname", 1234, "help message for flagname")
+If you like, you can bind the flag to a variable using the Var() functions.
+    var flagvar int
+    func init() {
+        flag.IntVar(&flagvar, "flagname", 1234, "help message for flagname")
+    }
+Or you can create custom flags that satisfy the Value interface (with
+pointer receivers) and couple them to flag parsing by
+    flag.Var(&flagVal, "name", "help message for flagname")
+For such flags, the default value is just the initial value of the variable.
+
+After all flags are defined, call
+    flag.Parse()
+to parse the command line into the defined flags.
+
+Flags may then be used directly. If you're using the flags themselves,
+they are all pointers; if you bind to variables, they're values.
+    fmt.Println("ip has value ", *ip);
+    fmt.Println("flagvar has value ", flagvar);
+
+After parsing, the arguments after the flag are available as the
+slice flag.Args() or individually as flag.Arg(i).
+The arguments are indexed from 0 up to flag.NArg().
+
+The pflag package also defines some new functions that are not in flag,
+that give one-letter shorthands for flags. You can use these by appending
+'P' to the name of any function that defines a flag.
+    var ip = flag.IntP("flagname", "f", 1234, "help message")
+    var flagvar bool
+    func init() {
+        flag.BoolVarP("boolname", "b", true, "help message")
+    }
+    flag.VarP(&flagVar, "varname", "v", 1234, "help message")
+Shorthand letters can be used with single dashes on the command line.
+Boolean shorthand flags can be combined with other shorthand flags.
+
+Command line flag syntax:
+    --flag    // boolean flags only
+    --flag=x
+    --flag x  // non-boolean flags only
+The last form is not permitted for boolean flags because the
+meaning of the command
+    cmd --flag *
+will change if there is a file called 0, false, etc.  You must
+use the --flag=false form to turn off a boolean flag.
+
+Unlike the flag package, a single dash before an option means something
+different than a double dash. Single dashes signify a series of shorthand
+letters for flags. All but the last shorthand letter must be boolean flags.
+    -f          // f must be boolean
+    -abc        // all flags must be boolean
+    -abcn=1234
+    -abcn 1234  // n must be non-boolean
+    -abcn1234   // n must be non-boolean
+    -Ifile      // I must be non-boolean
+
+Flag parsing stops after the terminator "--". Unlike the flag package,
+flags can be interspersed with arguments anywhere on the command line
+before this terminator.
+
+Integer flags accept 1234, 0664, 0x1234 and may be negative.
+Boolean flags may be 1, 0, t, f, true, false, TRUE, FALSE, True, False.
+Duration flags accept any input valid for time.ParseDuration.
+
+The default set of command-line flags is controlled by
+top-level functions.  The FlagSet type allows one to define
+independent sets of flags, such as to implement subcommands
+in a command-line interface. The methods of FlagSet are
+analogous to the top-level functions for the command-line
+flag set.
+
+## More info
+
+You can get a full reference of the pflag package through go's standard
+documentation system, for example by running `godoc -http=:6060` and
+browsing to http://localhost:6060/pkg/github.com/ogier/pflag after
+installation.