[libvirt] [PATCH 4/6] command: Add virCommandExec helper

[Cole Robinson]

Actually execs the argv/env we've generated, replacing the current process.
Kind of has a limited usage, but allows us to use virCommand in LXC
driver to launch the 'init' process

Signed-off-by: Cole Robinson <crobinso at redhat.com>
---
 src/libvirt_private.syms |    1 +
 src/util/command.c       |   22 ++++++++++++++++++++++
 src/util/command.h       |   10 ++++++++++
 3 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index d89b191..6e96692 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -106,6 +106,7 @@ virCommandAddEnvPassCommon;
 virCommandAddEnvString;
 virCommandClearCaps;
 virCommandDaemonize;
+virCommandExec;
 virCommandFree;
 virCommandNew;
 virCommandNewArgList;
diff --git a/src/util/command.c b/src/util/command.c
index ff4869d..78586e8 100644
--- a/src/util/command.c
+++ b/src/util/command.c
@@ -980,6 +980,28 @@ cleanup:
     return ret;
 }
 
+/*
+ * Exec the command, replacing the current process. Meant to be called
+ * after already forking / cloning, so does not attempt to daemonize or
+ * preserve any FDs.
+ *
+ * Returns -1 on any error executing the command.
+ * Will not return on success.
+ */
+int virCommandExec(virCommandPtr cmd)
+{
+    if (!cmd ||cmd->has_error == ENOMEM) {
+        virReportOOMError();
+        return -1;
+    }
+    if (cmd->has_error) {
+        virCommandError(VIR_ERR_INTERNAL_ERROR, "%s",
+                        _("invalid use of command API"));
+        return -1;
+    }
+
+    return execve(cmd->args[0], cmd->args, cmd->env);
+}
 
 /*
  * Run the command and wait for completion.
diff --git a/src/util/command.h b/src/util/command.h
index 69e9169..aa5136b 100644
--- a/src/util/command.h
+++ b/src/util/command.h
@@ -256,6 +256,16 @@ char *virCommandToString(virCommandPtr cmd) ATTRIBUTE_RETURN_CHECK;
 char *virCommandTranslateStatus(int exitstatus) ATTRIBUTE_RETURN_CHECK;
 
 /*
+ * Exec the command, replacing the current process. Meant to be called
+ * after already forking / cloning, so does not attempt to daemonize or
+ * preserve any FDs.
+ *
+ * Returns -1 on any error executing the command.
+ * Will not return on success.
+ */
+int virCommandExec(virCommandPtr cmd) ATTRIBUTE_RETURN_CHECK;
+
+/*
  * Run the command and wait for completion.
  * Returns -1 on any error executing the
  * command. Returns 0 if the command executed,
-- 
1.7.4.4