Add environment variable function

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@294 42af7a65-404d-4744-a932-0658087f49c3

ChangeLog

@@ -188,5 +188,7 @@
 	* Added basic OS support to manage environment variables:  environment
 	  storage, cloning on task creation, sharing on pthread creation, destruction
 	  on thread/task exit.
+	* Add environment variables APIs:  environ, getenv, putenv, clearenv, setenv,
+	  unsetenv
 	* Started m68322
 

Documentation/NuttX.html

@@ -623,6 +623,10 @@ Other memory:
 	* Added basic OS support to manage environment variables:  environment
 	  storage, cloning on task creation, sharing on pthread creation, destruction
 	  on thread/task exit.
+	* Add environment variables APIs:  environ, getenv, putenv, clearenv, setenv,
+	  unsetenv
+	* Add environment variables APIs:  environ, getenv, putenv, clearenv, setenv,
+	  unsetenv
 	* Started m68322
 </pre></ul>
 

include/nuttx/sched.h

@@ -154,7 +154,7 @@ struct environ_s
   unsigned int ev_crefs;      /* Reference count used when environment
                                * is shared by threads */
   size_t       ev_alloc;      /* Number of bytes allocated in environment */
-  ubyte        ev_env[1];     /* Environment strings */
+  char         ev_env[1];     /* Environment strings */
 };
 typedef struct environ_s environ_t;
 # define SIZEOF_ENVIRON_T(alloc) (sizeof(environ_t) + alloc - 1)

sched/Makefile

@@ -56,7 +56,8 @@ SCHED_SRCS	= sched_setparam.c sched_getparam.c \
 		  sched_getprioritymax.c sched_getprioritymin.c \
 		  sched_lock.c sched_unlock.c sched_lockcount.c
 ENV_SRCS	= env_getenvironptr.c env_dup.c env_share.c env_release.c \
-		  env_clearenv.c
+		  env_findvar.c env_removevar.c \
+		  env_clearenv.c env_getenv.c env_putenv.c env_setenv.c env_unsetenv.c
 WDOG_SRCS	= wd_initialize.c wd_create.c wd_start.c wd_cancel.c wd_delete.c \
 		  wd_gettime.c
 TIME_SRCS	= sched_processtimer.c

sched/env_clearenv.c

@@ -60,7 +60,7 @@
  * Description:
  *   The clearenv() function clears the environment of all name-value pairs
  *   and sets the value of the external variable environ to NULL.
-
+ *
  * Parameters:
  *   None
  *

sched/env_findvar.c

@@ -0,0 +1,126 @@
+/****************************************************************************
+ * env_findvar.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifndef CONFIG_DISABLE_ENVIRON
+
+#include <string.h>
+#include <sched.h>
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function: env_cmpname
+ ****************************************************************************/
+
+static boolean env_cmpname(const char *pszname, const char *peqname)
+{
+  /* Search until we find anything different in the two names */
+
+  for (; *pszname == *peqname; pszname++, peqname++);
+
+  /* On sucess, pszname will end with '\0' and peqname with '=' */
+
+  if ( *pszname == '\0' && *peqname == '=' )
+    {
+      return TRUE;
+    }
+  return FALSE;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  env_findvar
+ *
+ * Description:
+ *   Search the provided environment structure for the variable of the
+ *   specified name.
+ *
+ * Parameters:
+ *   envp The environment structre to be searched.
+ *   pname The variable name to find
+ *
+ * Return Value:
+ *   A pointer to the name=value string in the environment
+ *
+ * Assumptions:
+ *   - Not called from an interrupt handler
+ *   - Pre-emptions is disabled by caller
+ *
+ ****************************************************************************/
+
+FAR char *env_findvar(environ_t *envp, const char *pname)
+{
+  char *ret = NULL;
+
+  /* Verify input parameters */
+
+  if (envp && pname)
+    {
+      char *ptr;
+      char *end = &envp->ev_env[envp->ev_alloc];
+
+      /* Search for a name=value string with matching name */
+
+      for (ptr = envp->ev_env; ptr < end && !env_cmpname( pname, ptr); ptr += (strlen(ptr) + 1));
+
+      /* Check for success */
+
+      if (ptr < end)
+        {
+          ret = ptr;
+        }
+    }
+  return ret;
+}
+
+#endif /* CONFIG_DISABLE_ENVIRON */
+
+
+

sched/env_getenv.c

@@ -0,0 +1,136 @@
+/****************************************************************************
+ * env_getenv.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifndef CONFIG_DISABLE_ENVIRON
+
+#include <sched.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include "os_internal.h"
+#include "env_internal.h"
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  getenv
+ *
+ * Description:
+ *   The getenv() function searches the environment list for a string that
+ *   matches the string pointed to by name.
+ *
+ * Parameters:
+ *   name - The name of the variable to find. 
+ *
+ * Return Value:
+ *   The value of the valiable (read-only) or NULL on failure
+ *
+ * Assumptions:
+ *   Not called from an interrupt handler
+ *
+ ****************************************************************************/
+
+FAR char *getenv(const char *name)
+{
+  FAR _TCB      *rtcb;
+  FAR environ_t *envp;
+  FAR char      *pvar;
+  FAR char      *pvalue = NULL;
+  int ret = OK;
+
+  /* Verify that a string was passed */
+
+  if (!name)
+    {
+      ret = EINVAL;
+      goto errout;
+    }
+
+
+  /* Get a reference to the thread-private environ in the TCB.*/
+
+  sched_lock();
+  rtcb = (FAR _TCB*)g_readytorun.head;
+  envp = rtcb->envp;
+
+  /* Check if the variable exists */
+
+  if ( envp && (pvar = env_findvar(envp, name)) != NULL)
+    {
+      ret = ENOENT;
+      goto errout_with_lock;
+    }
+
+  /* It does!  Get the value sub-string from the name=value string */
+
+  pvalue = strchr(pvar, '=');
+  if (!pvalue)
+    {
+      /* The name=value string has no '='  This is a bug! */
+
+      ret = EINVAL;
+      goto errout_with_lock;
+    }
+
+  /* Adjust the pointer so that it points to the value right after the '=' */
+
+  pvalue++;
+  sched_unlock();
+  return pvalue;
+
+errout_with_lock:
+  sched_unlock();
+errout:
+  *get_errno_ptr() = ret;
+  return NULL;
+}
+
+#endif /* CONFIG_DISABLE_ENVIRON */
+
+
+

sched/env_internal.h

@@ -74,9 +74,16 @@ extern "C" {
 #endif
 
 #ifndef CONFIG_DISABLE_ENVIRON
+/* functions used by the task/pthread creation and destruction logic */
+
 EXTERN int env_dup(FAR _TCB *ptcb);
 EXTERN int env_share(FAR _TCB *ptcb);
 EXTERN int env_release(FAR _TCB *ptcb);
+
+/* functions used internally the environment handling logic */
+
+EXTERN FAR char *env_findvar(environ_t *envp, const char *pname);
+EXTERN int env_removevar(environ_t *envp, char *pvar);
 #endif
 
 #undef EXTERN

sched/env_putenv.c

@@ -0,0 +1,120 @@
+/****************************************************************************
+ * env_putenv.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifndef CONFIG_DISABLE_ENVIRON
+
+#include <sched.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  putenv
+ *
+ * Description:
+ *   The putenv() function adds or changes the value of environment variables.
+ *   The argument string is of the form name=value. If name does not already
+ *   exist in  the  environment, then string is added to the environment. If
+ *   name does exist, then the value of name in the environment is changed to
+ *   value.
+ *
+ * Parameters:
+ *   name=value string describing the environment setting to add/modify
+ *
+ * Return Value:
+ *   Zero on sucess
+ *
+ * Assumptions:
+ *   Not called from an interrupt handler
+ *
+ ****************************************************************************/
+
+int putenv(char *string)
+{
+  char *pname;
+  char *pequal;
+  int ret = OK;
+
+  /* Verify that a string was passed */
+
+  if (!string)
+    {
+      ret = EINVAL;
+      goto errout;
+    }
+
+  /* Parse the name=value string */
+
+  pname = strdup(string);
+  if (!pname)
+    {
+      ret = ENOMEM;
+      goto errout;
+    }
+
+  pequal = strchr( pname, '=');
+  if (pequal)
+    {
+      /* Then let setenv do all of the work */
+
+      *pequal = '\0';
+      ret = setenv(pname, pequal+1, TRUE);
+    }
+  free(pname);
+  return ret;
+
+errout:
+  *get_errno_ptr() = ret;
+  return ERROR;
+}
+
+#endif /* CONFIG_DISABLE_ENVIRON */
+
+
+

sched/env_removevar.c

@@ -0,0 +1,118 @@
+/****************************************************************************
+ * env_removevar.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifndef CONFIG_DISABLE_ENVIRON
+
+#include <string.h>
+#include <sched.h>
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  env_removevar
+ *
+ * Description:
+ *   Remove the referenced name=value pair from the environment
+ *
+ * Parameters:
+ *   envp The environment containing the name=value pair
+ *   pvar A pointer to the name=value pair in the restroom
+ *
+ * Return Value:
+ *   Zero on success
+ *
+ * Assumptions:
+ *   - Not called from an interrupt handler
+ *   - Caller has pre-emptions disabled
+ *   - Caller will reallocate the environment structure to the correct size
+ *
+ ****************************************************************************/
+
+int env_removevar(environ_t *envp, char *pvar)
+{
+  int ret = ERROR;
+  if (envp && pvar)
+    {
+      /* Verify that the pointer lies within the environment region */
+
+      int   alloc = envp->ev_alloc;       /* Size of the allocated environment */
+      char *end   = &envp->ev_env[alloc]; /* Pointer to the end+1 of the environment */
+
+      if (pvar >= envp->ev_env && pvar < end)
+        {
+          /* Set up for the removal */
+
+          int   len  = strlen(pvar) + 1;  /* Length of name=value string to remove */
+          char *src  = &pvar[len];        /* Address of name=value string after */
+          char *dest = pvar;              /* Location to move the next string */
+          int   count = end - src;         /* Number of bytes to move (might be zero) */
+
+          /* Move all of the environment strings after the removed one 'down.'
+           * this is inefficient, but robably not high duty.
+           */
+
+          while (count-- > 0)
+            {
+              *dest++ = *src++;
+            }
+
+          /* Then set to the new allocation size.  The caller is expected to
+           * call realloc at some point but we don't do that here because the
+           * caller may add more stuff to the environment.
+           */
+
+          envp->ev_alloc -= len;
+          ret = OK;
+        }
+    }
+  return ret;
+}
+
+#endif /* CONFIG_DISABLE_ENVIRON */
+
+
+

sched/env_setenv.c

@@ -0,0 +1,206 @@
+/****************************************************************************
+ * env_setenv.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifndef CONFIG_DISABLE_ENVIRON
+
+#include <stdio.h>
+#include <sched.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include "os_internal.h"
+#include "env_internal.h"
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  setenv
+ *
+ * Description:
+ *   The setenv() function adds the variable name to the environment with the
+ *   specified 'value' if the varialbe 'name" does not exist. If the 'name'
+ *   does exist in the environment, then its value is changed to 'value' if
+ *   'overwrite' is non-zero; if 'overwrite' is zero, then the value of name
+ *   unaltered.
+ *
+ * Parameters:
+ *   name - The name of the variable to change
+ *   value - The new value of the variable
+ *   overwrite - Replace any existing value if non-zero.
+ *
+ * Return Value:
+ *   Zero on success
+ *
+ * Assumptions:
+ *   Not called from an interrupt handler
+ *
+ ****************************************************************************/
+
+int setenv(const char *name, const char *value, int overwrite)
+{
+  FAR _TCB      *rtcb;
+  FAR environ_t *envp;
+  FAR char      *pvar;
+  int            varlen;
+  int ret = OK;
+
+  /* Verify input parameter */
+
+  if (!name)
+    {
+      ret = EINVAL;
+      goto errout;
+    }
+
+  /* if no value is provided, then this is the same as unsetenv (unless
+   * overwrite is false)
+   */
+
+  if (!value || *value == '\0')
+    {
+      /* If overwite is set then this is the same as unsetenv */
+
+      if (overwrite)
+        {
+          return unsetenv(name);
+        }
+      else
+        {
+          /* Otherwise, it is a request to remove a variable without altering it? */
+
+          return OK;
+        }
+    }
+
+  /* Get a reference to the thread-private environ in the TCB.*/
+
+  sched_lock();
+  rtcb = (FAR _TCB*)g_readytorun.head;
+  envp = rtcb->envp;
+
+  /* Check if the variable alreay exists */
+
+  if ( envp && (pvar = env_findvar(envp, name)) != NULL)
+    {
+      /* It does!  Do we have permission to overwrite the existing value? */
+
+      if (!overwrite)
+        {
+          /* No.. then just return success */
+
+          sched_unlock();
+          return OK;
+        }
+
+      /* Yes.. just remove the name=value pair from the environment.  It will
+       * be added again below.  Note that we are responsible for reallocating
+       * the environment buffer; this will happen below.
+       */
+
+      (void)env_removevar(envp, pvar);
+    }
+
+  /* Get the size of the new name=value string.  The +2 is for the '=' and for
+     * null terminator
+     */
+
+  varlen = strlen(name) + strlen(value) + 2;
+
+  /* Then allocate or reallocate the environment buffer */
+
+  if (envp)
+    {
+      int        alloc = envp->ev_alloc;
+      environ_t *tmp   = (environ_t*)realloc(envp, SIZEOF_ENVIRON_T(alloc + varlen));
+      if (!tmp)
+        {
+          ret = ENOMEM;
+          goto errout_with_lock;
+        }
+
+      envp           = tmp;
+      envp->ev_alloc = alloc + varlen;
+      pvar           = &envp->ev_env[alloc];
+    }
+  else
+    {
+      envp = (environ_t*)malloc(SIZEOF_ENVIRON_T(varlen));
+      if (!envp)
+        {
+          ret = ENOMEM;
+          goto errout_with_lock;
+        }
+
+      envp->ev_crefs = 1;
+      envp->ev_alloc = varlen;
+      pvar           = envp->ev_env;
+    }
+
+  /* Now, put the new name=value string into the environment buffer */
+
+  sprintf(pvar, "%s=%s", name, value);
+
+  /* Save the new environment pointer (it might have changed due to allocation or
+   * reallocation.
+   */
+
+  rtcb->envp = envp;
+  sched_unlock();
+  return OK;
+
+errout_with_lock:
+  sched_unlock();
+errout:
+  *get_errno_ptr() = ret;
+  return ERROR;
+}
+
+#endif /* CONFIG_DISABLE_ENVIRON */
+
+
+

sched/env_unsetenv.c

@@ -0,0 +1,137 @@
+/****************************************************************************
+ * env_unsetenv.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name Gregory Nutt nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifndef CONFIG_DISABLE_ENVIRON
+
+#include <sched.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include "os_internal.h"
+#include "env_internal.h"
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  unsetenv
+ *
+ * Description:
+ *   The unsetenv() function deletes the variable name from the environment.
+ *
+ * Parameters:
+ *   name - The name of the variable to delete
+ *
+ * Return Value:
+ *   Zero on success
+ *
+ * Assumptions:
+ *   Not called from an interrupt handler
+ *
+ ****************************************************************************/
+
+int unsetenv(const char *name)
+{
+  FAR _TCB      *rtcb;
+  FAR environ_t *envp;
+  FAR char      *pvar;
+  int ret = OK;
+
+  /* Verify input parameter */
+
+  if (!name)
+    {
+      ret = EINVAL;
+      goto errout;
+    }
+
+  /* Get a reference to the thread-private environ in the TCB.*/
+
+  sched_lock();
+  rtcb = (FAR _TCB*)g_readytorun.head;
+  envp = rtcb->envp;
+
+  /* Check if the variable exists */
+
+  if ( envp && (pvar = env_findvar(envp, name)) != NULL)
+    {
+      int        alloc;
+      environ_t *tmp;
+
+      /* It does!  Remove the name=value pair from the environment. */
+
+      (void)env_removevar(envp, pvar);
+
+      /* Reallocate the new environment buffer */
+
+      alloc = envp->ev_alloc;
+      tmp   = (environ_t*)realloc(envp, SIZEOF_ENVIRON_T(alloc));
+      if (!tmp)
+        {
+          ret = ENOMEM;
+          goto errout_with_lock;
+        }
+
+      /* Save the new environment pointer (it might have changed due to reallocation. */
+
+      rtcb->envp = tmp;
+    }
+
+  sched_unlock();
+  return OK;
+
+errout_with_lock:
+  sched_unlock();
+errout:
+  *get_errno_ptr() = ret;
+  return ERROR;
+}
+
+#endif /* CONFIG_DISABLE_ENVIRON */
+
+
+