Shell - Revision history

Michael: /* Add the function prototype to the include file */ syntax highlighting and corrections

2008-07-11T19:01:47Z

Add the function prototype to the include file: syntax highlighting and corrections

Michael: /* Add the function to the command table */ syntax highlighting

2008-07-11T19:01:17Z

Add the function to the command table: syntax highlighting

Michael: /* Write the function */ correction to params

2008-07-11T19:00:50Z

Write the function: correction to params

Michael: /* Add to header and makefile */ syntax highlighting and correction

2008-07-11T19:00:33Z

Add to header and makefile: syntax highlighting and correction

Michael: /* Write the function */ syntax highlighting

2008-07-11T18:59:32Z

Write the function: syntax highlighting

Brylow: /* Add the file to the Makefile */

2008-07-09T21:06:42Z

Add the file to the Makefile

Brylow: /* Add the file to the Makefile */

2008-07-09T21:06:07Z

Add the file to the Makefile

Brylow: New Makerules structure.

2008-07-09T21:04:42Z

New Makerules structure.

Agember: /* Example */ - Example is not unsafe

2007-09-20T23:30:00Z

Example: - Example is not unsafe

Michael: /* How it works */ split up into more paragraphs

2007-09-20T22:40:50Z

How it works: split up into more paragraphs

@@ Line 116: / Line 116: @@
 ==== Add the function prototype to the include file ====
 Next we must add the prototype of the function to the shell include file in <code>include/shell.h</code>. This is simply done by adding the line:
- command xsh_echo(ushort, ushort, ushort, ushort, char *[]);
+<source lang="c">
 ==== Add the file to the Makefile ====

@@ Line 109: / Line 109: @@
 ==== Add the function to the command table ====
 While we are in the <code>shell/</code> directory, we'll modify the command table found at the top of <code>shell/shell.c</code>.  Since we are adding the echo command, we'll most likely want the user input at the shell to be "<code>echo</code>," this is not a builtin function (FALSE), and the function that supports this is xsh_echo.  Giving us the entry:
- { "echo", FALSE, xsh_echo }
 ==== Add the function prototype to the include file ====

@@ Line 80: / Line 80: @@
   * @return OK for success, SYSERR for syntax error
   */
-command xsh_echo(ushort stdin, ushort stdout, ushort stderr, ushort nargs, char *args[])
+command xsh_echo(ushort nargs, char *args[])
+{
      int i;  /* counter for looping through arguments */

@@ Line 46: / Line 46: @@
 === Add to header and makefile ===
 To complete the process, add the function prototype to the shell header file <code>include/shell.h</code>:
-  command xsh_command( ushort, ushort, ushort, ushort, char *[]);
 Lastly, add the command function source file to the makefile (<code>shell/Makerules</code>) under the <code>C_FILES</code> group to ensure the command is compiled into the XINU boot image.

@@ Line 55: / Line 55: @@
 ==== Write the function ====
 Begin by creating the source file in <code>shell/xsh_echo.c</code>.  Since all commands take the same arguments (as passed by the shell), we get:
- /**
+<source lang="c">
-  * @file     xsh_echo.c
+/**
-  * @provides xsh_echo
+ * @file     xsh_echo.c
+ * @provides xsh_echo
-  * $Id$
-  */
+ * $Id$
- /* Embedded XINU, Copyright (C) 2007.  All rights reserved. */
+ */
 /* Embedded XINU, Copyright (C) 2007.  All rights reserved. */
- #include <kernel.h>
- #include <stdio.h>
+#include <kernel.h>
- #include <string.h>
+#include <stdio.h>
 #include <string.h>
- /**
-  * Shell command echos input text to standard out.
+/**
-  * @param stdin descriptor of input device
+ * Shell command echos input text to standard out.
-  * @param stdout descriptor of output device
+ * @param stdin descriptor of input device
-  * @param stderr descriptor of error device
+ * @param stdout descriptor of output device
-  * @param args array of arguments
+ * @param stderr descriptor of error device
-  * @return OK for success, SYSERR for syntax error
+ * @param args array of arguments
-  */
+ * @return OK for success, SYSERR for syntax error
- command xsh_echo(ushort stdin, ushort stdout, ushort stderr, ushort nargs, char *args[])
+ */
 command xsh_echo(ushort stdin, ushort stdout, ushort stderr, ushort nargs, char *args[])
-     int i;  /* counter for looping through arguments */
+    int i;  /* counter for looping through arguments */
-     /* Output help, if '--help' argument was supplied */
-     if (nargs == 2 && strncmp(args[1],"--help",6) == 0)
+    /* Output help, if '--help' argument was supplied */
+    if (nargs == 2 && strncmp(args[1],"--help",6) == 0)
-         fprintf(stdout, "Usage: clear\n");
-         fprintf(stdout, "Clears the terminal.\n");
+        fprintf(stdout, "Usage: clear\n");
-         fprintf(stdout, "\t--help\t display this help and exit\n");
+        fprintf(stdout, "Clears the terminal.\n");
-         return SYSERR;
+        fprintf(stdout, "\t--help\t display this help and exit\n");
+        return SYSERR;
-−
+    }
-     /* loop through the arguments printing each as it is displayed */
-     for ( i = 1; i < nargs; i++ )
+    /* loop through the arguments printing each as it is displayed */
+    for ( i = 1; i < nargs; i++ )
-         fprintf(stdout, "%s ", args[i]);
+        fprintf(stdout, "%s ", args[i]);
-−
+    }
-     /* Just so the next prompt doesn't run on to this line */
-     fprintf(stdout, "\n");
+    /* Just so the next prompt doesn't run on to this line */
+    fprintf(stdout, "\n");
-     /* there were no errors so, return OK */
-     return OK;
+    /* there were no errors so, return OK */
+    return OK;
 ==== Add the function to the command table ====

@@ Line 110: / Line 110: @@
 ==== Add the file to the Makefile ====
-Finally (and most importantly) we add the function to the Makefile to make sure that it is built by the compiler.  We do this by finding the line beginning with <code>C_FILES =</code> in <code>shell/Makerules</code> and adding
+Finally (and most importantly) we add the function to the Makefile to make sure that it is built by the compiler.  We do this by finding the line beginning with "<code>C_FILES =</code>" in <code>shell/Makerules</code> and adding
   xsh_echo.c
 to the end of it.
 Compile and run, and you should now have a working implementation of the <code>echo</code> command on your XINU system!

@@ Line 32: / Line 32: @@
 * the function prototype needs to be added to the header file (<code>include/shell.h</code>),
 * the command table (<code>shell/shell.c</code>) must be updated, and
-* the make file (<code>compile/Makefile</code>) must build the file containing the function.
+* the make file (<code>shell/Makerules</code>) must build the file containing the function.
 === Writing the function ===
@@ Line 48: / Line 48: @@
 To complete the process, add the function prototype to the shell header file <code>include/shell.h</code>:
    command xsh_command( ushort, ushort, ushort, ushort, char *[]);
-Lastly, add the command function source file to the makefile (<code>compile/Makefile</code>) to ensure the command is compiled into the XINU boot image.
+Lastly, add the command function source file to the makefile (<code>shell/Makerules</code>) under the <code>C_FILES</code> group to ensure the command is compiled into the XINU boot image.
 === Example ===

@@ Line 51: / Line 51: @@
 === Example ===
-We will run through a brief (and slightly unsafe) implementation of adding an echo command to the system.
+We will run through a brief implementation of adding an echo command to the system.
 ==== Write the function ====

@@ Line 4: / Line 4: @@
 The shell relies on the [[TTY_Driver | TTY driver]] to receive user input and provide output to the user.  When XINU starts, a shell process is spawned for each [[UART_Driver | serial port]] (or TTY).  When a user enters a command the [http://xinu.mscs.mu.edu/docs/lexan_8c.html <code>lexan</code>] function divides the string of input into tokens.  Command name, arguments, quoted strings, backgrounding, and redirection tokens are all recognized and divided by <code>lexan</code>.
-After the command is parsed, the shell uses the tokens to properly execute the given command.  The shell first checks for the backgrounding ampersand ('&'), which should only appear as the last token.  The shell is designed to handle redirection, but does not currently do so since XINU's file system is in development.  Next, the command is looked up in the command table defined at the top of <code>[http://xinu.mscs.mu.edu/docs/shell_8c.html shell/shell.c]</code>.  Each entry in the command table follows the format of command name, is the command built-in (ie can the command run in the background), and the function that executes the command: <code>{"command_name", TRUE / FALSE, xsh_function},</code>.  Built-in commands are executed by calling the function that implements the command.  All other commands are executed by creating a new process.  If the user did not include the backgrounding flag in the input, the shell waits until the command process has completed before asking for more input.
+After the command is parsed, the shell uses the tokens to properly execute the given command.  The shell first checks for the backgrounding ampersand ('&'), which should only appear as the last token.  The shell is designed to handle redirection, but does not currently do so since XINU's file system is in development.
 == Running commands ==