Radix cross Linux package tools

diff --git a/src/system.c b/src/system.c
new file mode 100644
index 0000000..c6e7b21
--- /dev/null
+++ b/src/system.c
@@ -0,0 +1,136 @@
+
+/**********************************************************************
+
+  Copyright 2019 Andrey V.Kosteltsev
+
+  Licensed under the Radix.pro License, Version 1.0 (the "License");
+  you may not use this file  except  in compliance with the License.
+  You may obtain a copy of the License at
+
+     https://radix.pro/licenses/LICENSE-1.0-en_US.txt
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+  implied.
+
+ **********************************************************************/
+
+#include <config.h>
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <error.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <stdarg.h>
+#include <unistd.h>
+
+#include <msglog.h>
+
+
+static void xexec( const char *cmd )
+{
+  char *argv[4];
+  const char *shell = getenv ("SHELL");
+
+  if( !shell ) shell = "/bin/sh";
+
+  argv[0] = (char *) shell;
+  argv[1] = (char *) "-c";
+  argv[2] = (char *) cmd;
+  argv[3] = NULL;
+
+  execv( shell, argv );
+
+  /******************************************
+    xexec() is called by child process, and
+    here child process faced to FATAL error:
+   */
+  logmsg( errlog, MSG_FATAL, "%s: Cannot exec", cmd );
+  exit( EXIT_FAILURE );
+}
+
+static pid_t xfork( void )
+{
+  pid_t p = fork();
+
+  if( p == (pid_t) -1 )
+  {
+    FATAL_ERROR( "Cannot %s", "fork" );
+  }
+
+  return p;
+}
+
+pid_t sys_exec_command( const char *cmd )
+{
+  pid_t pid = xfork();
+
+  if( pid != 0 )
+  {
+    return pid;
+  }
+
+  xexec( cmd );
+  return pid; /* only to avoid compilaton warning */
+}
+
+
+/*****************************************************************
+  sys_wait_command() - Wait for pid.
+
+  Return values:
+  -------------
+     0  - SUCCESS
+   >=1  - status returned by child process
+    -1  - Child terminated on signal
+    -2  - Child terminated on unknown reason
+    -3  - Cannot waitpid: waitpid() retusrs -1
+
+     Error message with SIZE length saved into *ERRMSG buffer.
+ *****************************************************************/
+int sys_wait_command( pid_t pid, char *errmsg, size_t size )
+{
+  int status;
+
+  if( pid < 0 ) return (pid_t) -1;
+
+  while( waitpid( pid, &status, 0 ) == -1 )
+    if( errno != EINTR )
+    {
+      if( errmsg && size ) {
+        (void)snprintf( errmsg, size, "PID %lu: Cannot %s", (unsigned long)pid, "waitpid" );
+      }
+      return (int) -3;
+    }
+
+  if( WIFEXITED( status ) )
+  {
+    if( WEXITSTATUS (status) )
+    {
+      if( errmsg && size ) {
+        (void)snprintf( errmsg, size, "PID %lu: Child returned status %d", (unsigned long)pid, WEXITSTATUS( status ) );
+      }
+      return (int) WEXITSTATUS( status );
+    }
+  }
+  else if( WIFSIGNALED( status ) )
+  {
+    if( errmsg && size ) {
+      (void)snprintf( errmsg, size, "PID %lu: Child terminated on signal %d", (unsigned long)pid, WTERMSIG( status ) );
+    }
+    return (int) -1;
+  }
+  else
+  {
+    if( errmsg && size ) {
+      (void)snprintf( errmsg, size, "PID %lu: Child terminated on unknown reason", (unsigned long)pid );
+    }
+    return (int) -2;
+  }
+
+  return 0;
+}