add --version flag, which prints "1.0"v1.0

For printing the current version, nsdo now accepts --version/-V. I've
updated the manpage to reflect this.

3 files changed, 33 insertions, 9 deletions

diff --git a/README.md b/README.md
index a4e59db..cca2b7f 100644
--- a/README.md
+++ b/README.md
@@ -54,14 +54,14 @@ manpage
 
     nsdo(1)               General Commands Manual              nsdo(1)
     
-    
-    
     NAME
            nsdo - run a command in a network namespace
     
     SYNOPSIS
            nsdo namespace command [args ...]
     
+           nsdo { --version | -V }
+    
     DESCRIPTION
            Execute  command  as the current user/group in namespace, a
            Linux network namespace  set  up  with  iproute2  (see  ip-
@@ -74,9 +74,12 @@ manpage
            rent namespace exists in that directory.  Consequently, you
            can not nest instances of nsdo.
     
+    OPTIONS
+           --version, -V
+                  Instead of running a command, print  nsdo's  version
+                  and exit.
+    
     SEE ALSO
            ip(8), ip-netns(8), namespaces(7)
     
-    
-    
-                                2015-08-08                     nsdo(1)
+                                2016-01-23                     nsdo(1)
diff --git a/nsdo.1 b/nsdo.1
index d212e99..3926453 100644
--- a/nsdo.1
+++ b/nsdo.1
@@ -1,15 +1,21 @@
-.TH nsdo 1 2015-08-08
+.TH nsdo 1 2016-01-23
 .SH NAME
 nsdo \- run a command in a network namespace
 .SH SYNOPSIS
 .B nsdo
 .I namespace command
 [\fIargs\fR ...]
+.PP
+.B nsdo
+{ --version | -V }
 .SH DESCRIPTION
 Execute \fIcommand\fR as the current user/group in \fInamespace\fR, a Linux network namespace set up with \fBiproute2\fR (see \fBip-netns(8)\fR).
 .PP 
 By default, \fBiproute2\fR places network namespaces in /var/run/netns/, so \fBnsdo\fR searces for namespaces there (including \fInamespace\fR).
 To prevent \fIcommand\fR from easily escaping the namespace 'jail,' \fBnsdo\fR will exit if the current namespace exists in that directory. 
 Consequently, you can not nest instances of \fBnsdo\fR.
+.SH OPTIONS
+.IP "--version, -V"
+Instead of running a command, print \fBnsdo\fR's version and exit.
 .SH SEE ALSO
 .B ip(8), ip-netns(8), namespaces(7)
diff --git a/nsdo.c b/nsdo.c
index fbc31e5..7291641 100644
--- a/nsdo.c
+++ b/nsdo.c
@@ -35,8 +35,11 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 
-#define NS_PATH "/var/run/netns"
 #define PROGRAM "nsdo"
+#define VERSION "1.0"
+#define NS_PATH "/var/run/netns"
+#define VERSION_FLAG "--version"
+#define VERSION_FLAG_SHORT "-V"
 
 enum {
     EXIT_OK,
@@ -54,8 +57,17 @@ enum {
     ARG_MIN_ARGS
 };
 
+void print_version() {
+    puts(PROGRAM " version " VERSION);
+}
+
 void print_usage() {
-    fprintf(stderr, "usage: " PROGRAM " <namespace> <command> [args...]\n");
+    fprintf(stderr, "usage: " PROGRAM " <namespace> <command> [args...]\n"
+                    "       " PROGRAM " { " VERSION_FLAG " | " VERSION_FLAG_SHORT " }\n");
+}
+
+int is_version_flag(char *arg) {
+    return !strcmp(arg, VERSION_FLAG) || !strcmp(arg, VERSION_FLAG_SHORT);
 }
 
 int current_ns_inode(ino_t *inode) {
@@ -193,7 +205,10 @@ int run(char *cmd, char **argv) {
 }
 
 int main(int argc, char **argv) {
-    if (argc < ARG_MIN_ARGS) {
+    if (argc-1 == 1 && is_version_flag(argv[1])) {
+        print_version();
+        return EXIT_OK;
+    } else if (argc < ARG_MIN_ARGS) {
         print_usage();
         return EXIT_BAD_INVOCATION;
     }