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document environment variables 

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@299 7fd9a85b-ad96-42d3-883c-3090e2eb8679
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2
nuttx/Documentation/NuttX.html
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@ -8,7 +8,7 @@
<tr align="center" bgcolor="#e4e4e4">
<td>
<h1><big><font color="#3c34ec"><i>NuttX RTOS</i></font></big></h1>
<p>Last Updated: June 9, 2007</p>
<p>Last Updated: June 30, 2007</p>
</td>
</tr>
</table>

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nuttx/Documentation/NuttxUserGuide.html
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@ -21,7 +21,7 @@ User's Manual
<p>
Gregory Nutt
<p>
<small>Last Update: May 27, 2007</small>
<small>Last Update: June 30, 2007</small>
</center>
<h1>1.0 <A NAME="Introduction">Introduction</a></h1>
@ -53,7 +53,8 @@ Gregory Nutt
<li>Paragraph 2.7 <a href="#ClocksNTimers">Clocks and Timers</a></li>
<li>Paragraph 2.8 <a href="#Signals">Signal Interfaces</a></li>
<li>Paragraph 2.9 <a href="#Pthread">Pthread Interfaces</a></li>
<li>Paragraph 2.10 <a href="#FileSystem">Filesystem Interfaces</a></li>
<li>Paragraph 2.10 <a href="#Environ">Environment Variables</a></li>
<li>Paragraph 2.11 <a href="#FileSystem">Filesystem Interfaces</a></li>
</ul>
</li>
<li>
@ -2208,9 +2209,7 @@ queue. The specified watchdog function will be called from the
interrupt level after the specified number of ticks has elapsed.
Watchdog timers may be started from the interrupt level.
<p>
Watchdog times execute in the context of the timer interrupt handler, but
with the PIC/PID address environment that was in place when wd_start()
was called.
Watchdog times execute in the context of the timer interrupt handler.
<p>
Watchdog timers execute only once.
<p>
@ -5502,6 +5501,272 @@ interface of the same name.
<b>POSIX Compatibility:</b> Comparable to the POSIX interface of the same name.
</p>
<h1><a name="Environ">2.10 Environment Variables</a></h1>
<p><b>Overview</b>.
NuttX supports environment variables that can be used to control the behavior of programs.
In the spirit of NuttX the environment variable behavior attempts to emulate the behavior of
environment variables in the mulit-processing OS:
</p>
<ul>
<li><b>Task environments</b>.
When a new task is created using <a href="#taskcreate">task_create</a>, the environment
of the child task is an inherited, exact copy of the environment of the parent.
However, after child task has been created, subsequent operations by the child task on
its environment does not alter the environment of the parent.
No do operations by the parent effect the child's environment.
The environments start identical but are independent and may diverge.
</li>
<li><b>Thread environments</b>.
When a pthread is created using <a href="#pthreadcreate">pthread_create</a>, the child
thread also inherits that envirnment of the parent.
However, the child does not recieve a copy of the environment but, rather, shares the same
environment.
Changes to the environment are visiable to all threads with the same parentage.
</li>
</ul>
<p><b>Programming Interfaces</b>.
The following environment variable programming interfaces are provided by Nuttx and are
described in detail in the following paragraphs.
</p>
<ul>
<li><a href="#getenv">2.10.1 <code>getenv</code></a></li>
<li><a href="#putenv">2.10.2 <code>putenv</code></a></li>
<li><a href="#clearenv">2.10.3 <code>clearenv</code></a></li>
<li><a href="#setenv">2.10.4 <code>setenv</code></a></li>
<li><a href="#unsetenv">2.10.5 <code>unsetenv</code></a></li>
</ul>
<p><b>Disabling Environment Variable Support</b>.
All support for environment variables can be disabled by setting <code>CONFIG_DISABLE_ENVIRONMENT</code>
in the board configuration file.
</p>
<h2><a name="getenv">2.10.1 <code>getenv</code></a></h2>
<p>
<b>Function Prototype:</b>
</p>
<pre>
#include <stdlib.h>
FAR char *getenv(const char *name);
</pre>
<p>
<b>Description:</b>
The <code>getenv()</code> function searches the environment list for a string that
matches the string pointed to by <code>name</code>.
</p>
<p>
<b>Input Parameters:</b>
</p>
<p>
<ul>
<li>
<code>name</code>.
The name of the variable to find.
</li>
</ul>
<p>
<b>Returned Values:</b>
The value of the valiable (read-only) or NULL on failure.
</p>
<h2><a name="putenv">2.10.2 <code>putenv</code></a></h2>
<p>
<b>Function Prototype:</b>
</p>
<pre>
#include <stdlib.h>
int putenv(char *string);
</pre>
<p>
<b>Description:</b>
The <code>putenv()</code> function adds or changes the value of environment variables.
The argument string is of the form <i>name=value</i>. 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.
</p>
<p>
<b>Input Parameters:</b>
</p>
<p>
<ul>
<li>
<code>string</code>
name=value string describing the environment setting to add/modify.
</li>
</ul>
<p>
<b>Returned Values:</b>
Zero on sucess.
</p>
<h2><a name="clearenv">2.10.3 <code>clearenv</code></a></h2>
<p>
<b>Function Prototype:</b>
</p>
<pre>
#include <stdlib.h>
int clearenv(void);
</pre>
<p>
<b>Description:</b>
The <code>clearenv()</code> function clears the environment of all name-value pairs
and sets the value of the external variable environ to NULL.
</p>
<p>
<b>Input Parameters:</b>
None
</p>
<p>
<b>Returned Values:</b>
Zero on success.
</p>
<h2><a name="setenv">2.10.4 <code>setenv</code></a></h2>
<p>
<b>Function Prototype:</b>
</p>
<pre>
#include <stdlib.h>
int setenv(const char *name, const char *value, int overwrite);
</pre>
<p>
<b>Description:</b>
The <code>setenv()</code> function adds the variable <code>name</code> to the environment with the
specified <code>value</code> if the variable <code>name</code> does not exist. If the <code>name</code>
does exist in the environment, then its value is changed to <code>value</code> if <code>overwrite</code>
is non-zero; if <code>overwrite</code> is zero, then the value of <code>name</code> is unaltered.
</p>
<p>
<b>Input Parameters:</b>
</p>
<p>
<ul>
<li>
<code>name</code>
The name of the variable to change.
</li>
<li>
<code>value</code>
The new value of the variable.
</li>
<li>
<code>value</code>
Replace any existing value if non-zero.
</li>
</ul>
<p>
<b>Returned Values:</b>
Zero on success.
</p>
<h2><a name="unsetenv">2.10.5 <code>unsetenv</code></a></h2>
<p>
<b>Function Prototype:</b>
</p>
<pre>
#include <stdlib.h>
int unsetenv(const char *name);
</pre>
<p>
<b>Description:</b>
The <code>unsetenv()</code> function deletes the variable <code>name</code> from the environment.
</p>
<p>
<b>Input Parameters:</b>
</p>
<p>
<ul>
<li>
<code>name</code>
The name of the variable to delete.
</li>
</ul>
<p>
<b>Returned Values:</b>
Zero on success.
</p>
<h1><a name="FileSystem">2.11 Filesystem Interfaces</a></h1>
<p>
The NuttX filesystem is very simple; it does not involve any block drivers or
particular filesystem (like FAT or EXT2 etc.).
The NuttX filesystem simply supports a set a filesystem APIs
(<code>open()</code>, <code>close()</code>, <code>read()</code>, <code>write</code>, etc.)
and a registration mechanism that allows devices drivers to a associated with <i>nodes</i>
in a file-system-like name space.
</p>
<h2><a name="driveroperations">2.11.1 Driver Operations</a></h2>
<ul><pre>
#include &lt;fcntl.h&gt;
int open(const char *path, int oflag, ...);
</pre></ul>
<ul><pre>
#include &lt;unistd.h&gt;
int close(int fd);
int dup(int fildes);
int dup2(int fildes1, int fildes2);
off_t lseek(int fd, off_t offset, int whence);
int read(int fd, void *buf, unsigned int nbytes);
int unlink(const char *path);
int write(int fd, const void *buf, unsigned int nbytes);
</pre></ul>
<ul><pre>
#include &lt;sys/ioctl.h&gt;
int ioctl(int fd, int req, unsigned long arg);
</pre></ul>
<h2><a name="directoryoperations">2.11.2 Directory Operations</a></h2>
<ul><pre>
#include &lt;dirent.h&gt;
int closedir(DIR *dirp);
FAR DIR *opendir(const char *path);
FAR struct dirent *readdir(FAR DIR *dirp);
int readdir_r(FAR DIR *dirp, FAR struct dirent *entry, FAR struct dirent **result);
void rewinddir(FAR DIR *dirp);
void seekdir(FAR DIR *dirp, int loc);
int telldir(FAR DIR *dirp);
</pre></ul>
<h2><a name="standardio">2.11.3 Standard I/O</a></h2>
<ul><pre>
#include &lt;stdio.h&gt;
int fclose(FILE *stream);
int fflush(FILE *stream);
int feof(FILE *stream); /* Prototyped but not implemented */
int ferror(FILE *stream); /* Prototyped but not implemented */
int fgetc(FILE *stream);
char *fgets(char *s, int n, FILE *stream);
FILE *fopen(const char *path, const char *type);
int fprintf(FILE *stream, const char *format, ...);
int fputc(int c, FILE *stream);
int fputs(const char *s, FILE *stream);
size_t fread(void *ptr, size_t size, size_t n_items, FILE *stream);
int fseek(FILE *stream, long int offset, int whence); /* Prototyped but not implemented */
size_t fwrite(const void *ptr, size_t size, size_t n_items, FILE *stream);
char *gets(char *s);
int printf(const char *format, ...);
int puts(const char *s);
int rename(const char *source, const char *target);
int sprintf(char *dest, const char *format, ...);
int ungetc(int c, FILE *stream);
int vprintf(const char *s, va_list ap);
int vfprintf(FILE *stream, const char *s, va_list ap);
int vsprintf(char *buf, const char *s, va_list ap);
int chdir(const char *path); /* Prototyped but not implemented */
FILE *fdopen(int fd, const char *type);
int fstat(int fd, FAR struct stat *buf); /* Prototyped but not implemented */
char *getcwd(FAR char *buf, size_t size); /* Prototyped but not implemented */
int mkdir(const char *path, mode_t mode);
int rmdir(const char *path);
int stat(const char *path, FAR struct stat *buf);
int statfs(const char *path, FAR struct statfs *buf); /* Prototyped but not implemented */
</pre></ul>
<hr>
<h1>3.0 <A NAME="Data_Structures">OS Data Structures</a></h1>
<H2>3.1 Scalar types</H2>
@ -5704,87 +5969,6 @@ notify a task when a message is available on a queue.
have to do some redesign.
</p>
<h1><a name="FileSystem">2.10 Filesystem Interfaces</a></h1>
<p>
The NuttX filesystem is very simple; it does not involve any block drivers or
particular filesystem (like FAT or EXT2 etc.).
The NuttX filesystem simply supports a set a filesystem APIs
(<code>open()</code>, <code>close()</code>, <code>read()</code>, <code>write</code>, etc.)
and a registration mechanism that allows devices drivers to a associated with <i>nodes</i>
in a file-system-like name space.
</p>
<h2><a name="driveroperations">2.10.1 Driver Operations</a></h2>
<ul><pre>
#include &lt;fcntl.h&gt;
int open(const char *path, int oflag, ...);
</pre></ul>
<ul><pre>
#include &lt;unistd.h&gt;
int close(int fd);
int dup(int fildes);
int dup2(int fildes1, int fildes2);
off_t lseek(int fd, off_t offset, int whence);
int read(int fd, void *buf, unsigned int nbytes);
int unlink(const char *path);
int write(int fd, const void *buf, unsigned int nbytes);
</pre></ul>
<ul><pre>
#include &lt;sys/ioctl.h&gt;
int ioctl(int fd, int req, unsigned long arg);
</pre></ul>
<h2><a name="directoryoperations">2.10.2 Directory Operations</a></h2>
<ul><pre>
#include &lt;dirent.h&gt;
int closedir(DIR *dirp);
FAR DIR *opendir(const char *path);
FAR struct dirent *readdir(FAR DIR *dirp);
int readdir_r(FAR DIR *dirp, FAR struct dirent *entry, FAR struct dirent **result);
void rewinddir(FAR DIR *dirp);
void seekdir(FAR DIR *dirp, int loc);
int telldir(FAR DIR *dirp);
</pre></ul>
<h2><a name="standardio">2.10.3 Standard I/O</a></h2>
<ul><pre>
#include &lt;stdio.h&gt;
int fclose(FILE *stream);
int fflush(FILE *stream);
int feof(FILE *stream); /* Prototyped but not implemented */
int ferror(FILE *stream); /* Prototyped but not implemented */
int fgetc(FILE *stream);
char *fgets(char *s, int n, FILE *stream);
FILE *fopen(const char *path, const char *type);
int fprintf(FILE *stream, const char *format, ...);
int fputc(int c, FILE *stream);
int fputs(const char *s, FILE *stream);
size_t fread(void *ptr, size_t size, size_t n_items, FILE *stream);
int fseek(FILE *stream, long int offset, int whence); /* Prototyped but not implemented */
size_t fwrite(const void *ptr, size_t size, size_t n_items, FILE *stream);
char *gets(char *s);
int printf(const char *format, ...);
int puts(const char *s);
int rename(const char *source, const char *target);
int sprintf(char *dest, const char *format, ...);
int ungetc(int c, FILE *stream);
int vprintf(const char *s, va_list ap);
int vfprintf(FILE *stream, const char *s, va_list ap);
int vsprintf(char *buf, const char *s, va_list ap);
int chdir(const char *path); /* Prototyped but not implemented */
FILE *fdopen(int fd, const char *type);
int fstat(int fd, FAR struct stat *buf); /* Prototyped but not implemented */
char *getcwd(FAR char *buf, size_t size); /* Prototyped but not implemented */
int mkdir(const char *path, mode_t mode);
int rmdir(const char *path);
int stat(const char *path, FAR struct stat *buf);
int statfs(const char *path, FAR struct statfs *buf); /* Prototyped but not implemented */
</pre></ul>
<h1><a name="index">Index</a></h1>
<ul>
<li><a href="#clockgetres">clock_getres</a></li>

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nuttx/TODO
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@ -37,6 +37,8 @@ o USB
o Libraries
- sscanf() and lib_vsprintf() do not support floating point values.
- The definition of environ in stdlib.h is bogus and will not work as it should. This
is because the underlying representation of the environment is not an arry of pointers.
o File system
- Add chmod(), truncate().