--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toys/posix/sh.c	Sat Aug 25 16:34:08 2012 -0500
@@ -0,0 +1,390 @@
+/* vi: set sw=4 ts=4:
+ *
+ * sh.c - toybox shell
+ *
+ * Copyright 2006 Rob Landley <rob@landley.net>
+ *
+ * The POSIX-2008/SUSv4 spec for this is at:
+ * http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
+ * and http://www.opengroup.org/onlinepubs/9699919799/utilities/sh.html
+ *
+ * The first link describes the following shell builtins:
+ *
+ *   break colon continue dot eval exec exit export readonly return set shift
+ *   times trap unset
+ *
+ * The second link (the utilities directory) also contains specs for the
+ * following shell builtins:
+ *
+ *   alias bg cd command fc fg getopts hash jobs kill read type ulimit
+ *   umask unalias wait
+ *
+ * Things like the bash man page are good to read too.
+ *
+ * TODO: // Handle embedded NUL bytes in the command line.
+
+USE_SH(NEWTOY(cd, NULL, TOYFLAG_NOFORK))
+USE_SH(NEWTOY(exit, NULL, TOYFLAG_NOFORK))
+
+USE_SH(NEWTOY(sh, "c:i", TOYFLAG_BIN))
+USE_SH(OLDTOY(toysh, sh, "c:i", TOYFLAG_BIN))
+
+config SH
+	bool "sh (toysh)"
+	default n
+	help
+	  usage: sh [-c command] [script]
+
+	  Command shell.  Runs a shell script, or reads input interactively
+	  and responds to it.
+
+	  -c	command line to execute
+
+config SH_TTY
+	bool "Interactive shell (terminal control)"
+	default n
+	depends on SH
+	help
+	  Add terminal control to toysh.  This is necessary for interactive use,
+	  so the shell isn't killed by CTRL-C.
+
+config SH_PROFILE
+	bool "Profile support"
+	default n
+	depends on SH_TTY
+	help
+	  Read /etc/profile and ~/.profile when running interactively.
+
+	  Also enables the built-in command "source".
+
+config SH_JOBCTL
+	bool "Job Control (fg, bg, jobs)"
+	default n
+	depends on SH_TTY
+	help
+	  Add job control to toysh.  This lets toysh handle CTRL-Z, and enables
+	  the built-in commands "fg", "bg", and "jobs".
+
+	  With pipe support, enable use of "&" to run background processes.
+
+config SH_FLOWCTL
+	bool "Flow control (if, while, for, functions)"
+	default n
+	depends on SH
+	help
+	  Add flow control to toysh.  This enables the if/then/else/fi,
+	  while/do/done, and for/do/done constructs.
+
+	  With pipe support, this enables the ability to define functions
+	  using the "function name" or "name()" syntax, plus curly brackets
+	  "{ }" to group commands.
+
+config SH_QUOTES
+	bool "Smarter argument parsing (quotes)"
+	default n
+	depends on SH
+	help
+	  Add support for parsing "" and '' style quotes to the toysh command
+	  parser, with lets arguments have spaces in them.
+
+config SH_WILDCARDS
+	bool "Wildcards ( ?*{,} )"
+	default n
+	depends on SH_QUOTES
+	help
+	  Expand wildcards in argument names, ala "ls -l *.t?z" and
+	  "rm subdir/{one,two,three}.txt".
+
+config SH_PROCARGS
+	bool "Executable arguments ( `` and $() )"
+	default n
+	depends on SH_QUOTES
+	help
+	  Add support for executing arguments contianing $() and ``, using
+	  the output of the command as the new argument value(s).
+
+	  (Bash calls this "command substitution".)
+
+config SH_ENVVARS
+	bool "Environment variable support"
+	default n
+	depends on SH_QUOTES
+	help
+	  Substitute environment variable values for $VARNAME or ${VARNAME},
+	  and enable the built-in command "export".
+
+config SH_LOCALS
+	bool "Local variables"
+	default n
+	depends on SH_ENVVARS
+	help
+	  Support for local variables, fancy prompts ($PS1), the "set" command,
+	  and $?.
+
+config SH_ARRAYS
+	bool "Array variables"
+	default n
+	depends on SH_LOCALS
+	help
+	  Support for ${blah[blah]} style array variables.
+
+config SH_PIPES
+	bool "Pipes and redirects ( | > >> < << & && | || () ; )"
+	default n
+	depends on SH
+	help
+	  Support multiple commands on the same command line.  This includes
+	  | pipes, > >> < redirects, << here documents, || && conditional
+	  execution, () subshells, ; sequential execution, and (with job
+	  control) & background processes.
+
+config SH_BUILTINS
+	bool "Builtin commands"
+	default n
+	depends on SH
+	help
+	  Adds the commands exec, fg, bg, help, jobs, pwd, export, source, set,
+	  unset, read, alias.
+
+config EXIT
+	bool
+	default n
+	depends on SH
+	help
+	  usage: exit [status]
+
+	  Exit shell.  If no return value supplied on command line, use value
+	  of most recent command, or 0 if none.
+
+config CD
+	bool
+	default n
+	depends on SH
+	help
+	  usage: cd [path]
+
+	  Change current directory.  With no arguments, go to $HOME.
+
+config CD_P
+	bool # "-P support for cd"
+	default n
+	depends on SH
+	help
+	  usage: cd [-PL]
+
+	  -P    Physical path: resolve symlinks in path.
+	  -L    Cancel previous -P and restore default behavior.
+*/
+
+#include "toys.h"
+
+DEFINE_GLOBALS(
+	char *command;
+)
+
+#define TT this.sh
+
+// A single executable, its arguments, and other information we know about it.
+#define TOYSH_FLAG_EXIT    1
+#define TOYSH_FLAG_SUSPEND 2
+#define TOYSH_FLAG_PIPE    4
+#define TOYSH_FLAG_AND     8
+#define TOYSH_FLAG_OR      16
+#define TOYSH_FLAG_AMP     32
+#define TOYSH_FLAG_SEMI    64
+#define TOYSH_FLAG_PAREN   128
+
+// What we know about a single process.
+struct command {
+	struct command *next;
+	int flags;              // exit, suspend, && ||
+	int pid;                // pid (or exit code)
+	int argc;
+	char *argv[0];
+};
+
+// A collection of processes piped into/waiting on each other.
+struct pipeline {
+	struct pipeline *next;
+	int job_id;
+	struct command *cmd;
+	char *cmdline;         // Unparsed line for display purposes
+	int cmdlinelen;        // How long is cmdline?
+};
+
+// Parse one word from the command line, appending one or more argv[] entries
+// to struct command.  Handles environment variable substitution and
+// substrings.  Returns pointer to next used byte, or NULL if it
+// hit an ending token.
+static char *parse_word(char *start, struct command **cmd)
+{
+	char *end;
+
+	// Detect end of line (and truncate line at comment)
+	if (CFG_TOYSH_PIPES && strchr("><&|(;", *start)) return 0;
+
+	// Grab next word.  (Add dequote and envvar logic here)
+	end = start;
+	while (*end && !isspace(*end)) end++;
+	(*cmd)->argv[(*cmd)->argc++] = xstrndup(start, end-start);
+
+	// Allocate more space if there's no room for NULL terminator.
+
+	if (!((*cmd)->argc & 7))
+		*cmd=xrealloc(*cmd,
+				sizeof(struct command) + ((*cmd)->argc+8)*sizeof(char *));
+	(*cmd)->argv[(*cmd)->argc] = 0;
+	return end;
+}
+
+// Parse a line of text into a pipeline.
+// Returns a pointer to the next line.
+
+static char *parse_pipeline(char *cmdline, struct pipeline *line)
+{
+	struct command **cmd = &(line->cmd);
+	char *start = line->cmdline = cmdline;
+
+	if (!cmdline) return 0;
+
+	if (CFG_TOYSH_JOBCTL) line->cmdline = cmdline;
+
+	// Parse command into argv[]
+	for (;;) {
+		char *end;
+
+		// Skip leading whitespace and detect end of line.
+		while (isspace(*start)) start++;
+		if (!*start || *start=='#') {
+			if (CFG_TOYSH_JOBCTL) line->cmdlinelen = start-cmdline;
+			return 0;
+		}
+
+		// Allocate next command structure if necessary
+		if (!*cmd) *cmd = xzalloc(sizeof(struct command)+8*sizeof(char *));
+
+		// Parse next argument and add the results to argv[]
+		end = parse_word(start, cmd);
+
+		// If we hit the end of this command, how did it end?
+		if (!end) {
+			if (CFG_TOYSH_PIPES && *start) {
+				if (*start==';') {
+					start++;
+					break;
+				}
+				// handle | & < > >> << || &&
+			}
+			break;
+		}
+		start = end;
+	}
+
+	if (CFG_TOYSH_JOBCTL) line->cmdlinelen = start-cmdline;
+
+	return start;
+}
+
+// Execute the commands in a pipeline
+static void run_pipeline(struct pipeline *line)
+{
+	struct toy_list *tl;
+	struct command *cmd = line->cmd;
+	if (!cmd || !cmd->argc) return;
+
+	tl = toy_find(cmd->argv[0]);
+	// Is this command a builtin that should run in this process?
+	if (tl && (tl->flags & TOYFLAG_NOFORK)) {
+		struct toy_context temp;
+
+		// This fakes lots of what toybox_main() does.
+		memcpy(&temp, &toys, sizeof(struct toy_context));
+		memset(&toys, 0, sizeof(struct toy_context));
+		toy_init(tl, cmd->argv);
+		tl->toy_main();
+		cmd->pid = toys.exitval;
+		free(toys.optargs);
+		if (toys.old_umask) umask(toys.old_umask);
+		memcpy(&toys, &temp, sizeof(struct toy_context));
+	} else {
+		int status;
+
+		cmd->pid = vfork();
+		if (!cmd->pid) xexec(cmd->argv);
+		else waitpid(cmd->pid, &status, 0);
+
+		if (CFG_TOYSH_FLOWCTL || CFG_TOYSH_PIPES) {
+			if (WIFEXITED(status)) cmd->pid = WEXITSTATUS(status);
+			if (WIFSIGNALED(status)) cmd->pid = WTERMSIG(status);
+		}
+	}
+
+	return;
+}
+
+// Free the contents of a command structure
+static void free_cmd(void *data)
+{
+	struct command *cmd=(struct command *)data;
+
+	while(cmd->argc) free(cmd->argv[--cmd->argc]);
+}
+
+
+// Parse a command line and do what it says to do.
+static void handle(char *command)
+{
+	struct pipeline line;
+	char *start = command;
+
+	// Loop through commands in this line
+
+	for (;;) {
+
+		// Parse a group of connected commands
+
+		memset(&line,0,sizeof(struct pipeline));
+		start = parse_pipeline(start, &line);
+		if (!line.cmd) break;
+
+		// Run those commands
+
+		run_pipeline(&line);
+		llist_traverse(line.cmd, free_cmd);
+	}
+}
+
+void cd_main(void)
+{
+	char *dest = *toys.optargs ? *toys.optargs : getenv("HOME");
+	xchdir(dest);
+}
+
+void exit_main(void)
+{
+	exit(*toys.optargs ? atoi(*toys.optargs) : 0);
+}
+
+void sh_main(void)
+{
+	FILE *f;
+
+	// Set up signal handlers and grab control of this tty.
+	if (CFG_TOYSH_TTY) {
+		if (isatty(0)) toys.optflags |= 1;
+	}
+	f = *toys.optargs ? xfopen(*toys.optargs, "r") : NULL;
+	if (TT.command) handle(TT.command);
+	else {
+		size_t cmdlen = 0;
+		for (;;) {
+			char *command = 0;
+			if (!f) xputc('$');
+			if (1 > getline(&command, &cmdlen, f ? f : stdin)) break;
+			handle(command);
+			free(command);
+		}
+	}
+
+	toys.exitval = 1;
+}