cpukit/shell: Control help break with SHELL_LINES env variable.

Control the help command break with the SHELL_LINES evironment variable
where the numeric value is the number of lines to break on. If the
value is 0 the output is not broken. The default is 16 lines.

Add shell documentation for the help command.

cpukit/libmisc/shell/main_help.c

@@ -12,6 +12,7 @@
 #endif
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <time.h>
 
 #include <rtems.h>
@@ -79,10 +80,17 @@ static int rtems_shell_help(
   char * argv[]
 )
 {
-  int col,line,arg;
+  int col,line,lines,arg;
+  char* lines_env;
   rtems_shell_topic_t *topic;
   rtems_shell_cmd_t * shell_cmd = rtems_shell_first_cmd;
 
+  lines_env = getenv("SHELL_LINES");
+  if (lines_env)
+    lines = strtol(lines_env, 0, 0);
+  else
+    lines = 16;
+
   if (argc<2) {
     printf("help: ('r' repeat last cmd - 'e' edit last cmd)\n"
            "  TOPIC? The topics are\n");
@@ -106,7 +114,7 @@ static int rtems_shell_help(
   }
   line = 0;
   for (arg = 1;arg<argc;arg++) {
-    if (line>16) {
+    if (lines && (line > lines)) {
       printf("Press any key to continue...");getchar();
       printf("\n");
       line = 0;
@@ -127,7 +135,7 @@ static int rtems_shell_help(
     while (shell_cmd) {
       if (!strcmp(topic->topic,shell_cmd->topic))
         line+= rtems_shell_help_cmd(shell_cmd);
-      if (line>16) {
+      if (lines && (line > lines)) {
         printf("Press any key to continue...");
         getchar();
         printf("\n");

doc/shell/general.t

@@ -11,6 +11,7 @@ The RTEMS shell has the following general commands:
 
 @itemize @bullet
 
+@item @code{help} - Print command help
 @item @code{alias} - Add alias for an existing command
 @item @code{date} - Print or set current date and time
 @item @code{echo} - Produce message in a shell script
@@ -34,6 +35,87 @@ This section details the General Commands available.  A
 subsection is dedicated to each of the commands and
 describes the behavior and configuration of that
 command as well as providing an example usage.
+@c
+@c
+@c
+@page
+@subsection help - Print command help
+
+@pgindex help
+
+@subheading SYNOPSYS:
+
+@example
+help misc
+@end example
+
+@subheading DESCRIPTION:
+
+This command prints the command help. Help without arguments prints a
+list of topics and help with a topic prints the help for that topic.
+
+@subheading EXIT STATUS:
+
+This command returns 0.
+
+@subheading NOTES:
+
+The help print will break the output up based on the environment
+variable SHELL_LINES. If this environment variable is not set the
+default is 16 lines. If set the number of lines is set to that the
+value. If the shell lines is set 0 there will be no break.
+
+@subheading EXAMPLES:
+
+The following is an example of how to use @code{alias}:
+
+@example
+SHLL [/] $ help
+help: ('r' repeat last cmd - 'e' edit last cmd)
+  TOPIC? The topics are
+   mem, misc, files, help, rtems, network, monitor
+SHLL [/] $ help misc
+help: list for the topic 'misc'
+alias        - alias old new
+time         - time command [arguments...]
+joel         - joel [args] SCRIPT
+date         - date [YYYY-MM-DD HH:MM:SS]
+echo         - echo [args]
+sleep        - sleep seconds [nanoseconds]
+id           - show uid, gid, euid, and egid
+tty          - show ttyname
+whoami       - show current user
+logoff       - logoff from the system
+setenv       - setenv [var] [string]
+getenv       - getenv [var]
+unsetenv     - unsetenv [var]
+umask        - umask [new_umask]
+Press any key to continue...
+rtc          - real time clock read and set
+SHLL [/] $ setenv SHELL_ENV 0
+SHLL [/] $ help misc
+help: list for the topic 'misc'
+alias        - alias old new
+time         - time command [arguments...]
+joel         - joel [args] SCRIPT
+date         - date [YYYY-MM-DD HH:MM:SS]
+echo         - echo [args]
+sleep        - sleep seconds [nanoseconds]
+id           - show uid, gid, euid, and egid
+tty          - show ttyname
+whoami       - show current user
+logoff       - logoff from the system
+setenv       - setenv [var] [string]
+getenv       - getenv [var]
+unsetenv     - unsetenv [var]
+umask        - umask [new_umask]
+rtc          - real time clock read and set
+@end example
+
+@subheading CONFIGURATION:
+
+This command has no configuration.
+
 @c
 @c
 @c