1 /* sh.c - toybox shell
2  *
3  * Copyright 2006 Rob Landley <rob@landley.net>
4  *
5  * The POSIX-2008/SUSv4 spec for this is at:
6  * http://opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
7  * and http://opengroup.org/onlinepubs/9699919799/utilities/sh.html
8  *
9  * The first link describes the following shell builtins:
10  *
11  *   break colon continue dot eval exec exit export readonly return set shift
12  *   times trap unset
13  *
14  * The second link (the utilities directory) also contains specs for the
15  * following shell builtins:
16  *
17  *   alias bg cd command fc fg getopts hash jobs kill read type ulimit
18  *   umask unalias wait
19  *
20  * Things like the bash man page are good to read too.
21  *
22  * TODO: "make sh" doesn't work (nofork builtins need to be included)
23  * TODO: test that $PS1 color changes work without stupid \[ \] hack
24  * TODO: make fake pty wrapper for test infrastructure
25  * TODO: // Handle embedded NUL bytes in the command line.
26  * TODO: var=val command
27  * existing but considered builtins: false kill pwd true
28  * buitins: alias bg command fc fg getopts jobs newgrp read umask unalias wait
29  * "special" builtins: break continue : . eval exec export readonly return set
30  *   shift times trap unset
31  * | & ; < > ( ) $ ` \ " ' <space> <tab> <newline>
32  * * ? [ # ~ = %
33  * ! { } case do done elif else esac fi for if in then until while
34  * [[ ]] function select
35  * $@ $* $# $? $- $$ $! $0
36  * ENV HOME IFS LANG LC_ALL LINENO PATH PPID PS1 PS2 PS4 PWD
37  * label:
38  * TODO: test exit from "trap EXIT" doesn't recurse
39 
40 USE_SH(NEWTOY(cd, NULL, TOYFLAG_NOFORK))
41 USE_SH(NEWTOY(exit, NULL, TOYFLAG_NOFORK))
42 
43 USE_SH(NEWTOY(sh, "c:i", TOYFLAG_BIN))
44 USE_SH(OLDTOY(toysh, sh, TOYFLAG_BIN))
45 // Login lies in argv[0], so add some aliases to catch that
46 USE_SH(OLDTOY(-sh, sh, 0))
47 USE_SH(OLDTOY(-toysh, sh, 0))
48 
49 config SH
50   bool "sh (toysh)"
51   default n
52   help
53     usage: sh [-c command] [script]
54 
55     Command shell.  Runs a shell script, or reads input interactively
56     and responds to it.
57 
58     -c	command line to execute
59     -i	interactive mode (default when STDIN is a tty)
60 
61 config CD
62   bool
63   default n
64   depends on SH
65   help
66     usage: cd [-PL] [path]
67 
68     Change current directory.  With no arguments, go $HOME.
69 
70     -P	Physical path: resolve symlinks in path.
71     -L	Local path: .. trims directories off $PWD (default).
72 
73 config EXIT
74   bool
75   default n
76   depends on SH
77   help
78     usage: exit [status]
79 
80     Exit shell.  If no return value supplied on command line, use value
81     of most recent command, or 0 if none.
82 */
83 
84 #define FOR_sh
85 #include "toys.h"
86 
87 GLOBALS(
88   char *command;
89 
90   long lineno;
91 )
92 
93 // What we know about a single process.
94 struct command {
95   struct command *next;
96   int flags;              // exit, suspend, && ||
97   int pid;                // pid (or exit code)
98   int argc;
99   char *argv[0];
100 };
101 
102 // A collection of processes piped into/waiting on each other.
103 struct pipeline {
104   struct pipeline *next;
105   int job_id;
106   struct command *cmd;
107   char *cmdline;         // Unparsed line for display purposes
108   int cmdlinelen;        // How long is cmdline?
109 };
110 
cd_main(void)111 void cd_main(void)
112 {
113   char *dest = *toys.optargs ? *toys.optargs : getenv("HOME");
114 
115   xchdir(dest ? dest : "/");
116 }
117 
exit_main(void)118 void exit_main(void)
119 {
120   exit(*toys.optargs ? atoi(*toys.optargs) : 0);
121 }
122 
123 // Parse one word from the command line, appending one or more argv[] entries
124 // to struct command.  Handles environment variable substitution and
125 // substrings.  Returns pointer to next used byte, or NULL if it
126 // hit an ending token.
parse_word(char * start,struct command ** cmd)127 static char *parse_word(char *start, struct command **cmd)
128 {
129   char *end;
130 
131   // Detect end of line (and truncate line at comment)
132   if (strchr("><&|(;", *start)) return 0;
133 
134   // Grab next word.  (Add dequote and envvar logic here)
135   end = start;
136   while (*end && !isspace(*end)) end++;
137   (*cmd)->argv[(*cmd)->argc++] = xstrndup(start, end-start);
138 
139   // Allocate more space if there's no room for NULL terminator.
140 
141   if (!((*cmd)->argc & 7))
142     *cmd=xrealloc(*cmd,
143         sizeof(struct command) + ((*cmd)->argc+8)*sizeof(char *));
144   (*cmd)->argv[(*cmd)->argc] = 0;
145   return end;
146 }
147 
148 // Parse a line of text into a pipeline.
149 // Returns a pointer to the next line.
150 
parse_pipeline(char * cmdline,struct pipeline * line)151 static char *parse_pipeline(char *cmdline, struct pipeline *line)
152 {
153   struct command **cmd = &(line->cmd);
154   char *start = line->cmdline = cmdline;
155 
156   if (!cmdline) return 0;
157 
158   line->cmdline = cmdline;
159 
160   // Parse command into argv[]
161   for (;;) {
162     char *end;
163 
164     // Skip leading whitespace and detect end of line.
165     while (isspace(*start)) start++;
166     if (!*start || *start=='#') {
167       line->cmdlinelen = start-cmdline;
168       return 0;
169     }
170 
171     // Allocate next command structure if necessary
172     if (!*cmd) *cmd = xzalloc(sizeof(struct command)+8*sizeof(char *));
173 
174     // Parse next argument and add the results to argv[]
175     end = parse_word(start, cmd);
176 
177     // If we hit the end of this command, how did it end?
178     if (!end) {
179       if (*start) {
180         if (*start==';') {
181           start++;
182           break;
183         }
184         // handle | & < > >> << || &&
185       }
186       break;
187     }
188     start = end;
189   }
190 
191   line->cmdlinelen = start-cmdline;
192 
193   return start;
194 }
195 
196 // Execute the commands in a pipeline
run_pipeline(struct pipeline * line)197 static void run_pipeline(struct pipeline *line)
198 {
199   struct toy_list *tl;
200   struct command *cmd = line->cmd;
201   if (!cmd || !cmd->argc) return;
202 
203   tl = toy_find(cmd->argv[0]);
204 
205   // Is this command a builtin that should run in this process?
206   if (tl && (tl->flags & TOYFLAG_NOFORK)) {
207     struct toy_context temp;
208     jmp_buf rebound;
209 
210     // This fakes lots of what toybox_main() does.
211     memcpy(&temp, &toys, sizeof(struct toy_context));
212     memset(&toys, 0, sizeof(struct toy_context));
213 
214     if (!setjmp(rebound)) {
215       toys.rebound = &rebound;
216       toy_init(tl, cmd->argv);
217       tl->toy_main();
218     }
219     cmd->pid = toys.exitval;
220     if (toys.optargs != toys.argv+1) free(toys.optargs);
221     if (toys.old_umask) umask(toys.old_umask);
222     memcpy(&toys, &temp, sizeof(struct toy_context));
223   } else {
224     int status;
225 
226     cmd->pid = vfork();
227     if (!cmd->pid) xexec(cmd->argv);
228     else waitpid(cmd->pid, &status, 0);
229 
230     if (WIFEXITED(status)) cmd->pid = WEXITSTATUS(status);
231     if (WIFSIGNALED(status)) cmd->pid = WTERMSIG(status);
232   }
233 
234   return;
235 }
236 
237 // Free the contents of a command structure
free_cmd(void * data)238 static void free_cmd(void *data)
239 {
240   struct command *cmd=(struct command *)data;
241 
242   while(cmd->argc) free(cmd->argv[--cmd->argc]);
243 }
244 
245 
246 // Parse a command line and do what it says to do.
handle(char * command)247 static void handle(char *command)
248 {
249   struct pipeline line;
250   char *start = command;
251 
252   // Loop through commands in this line
253 
254   for (;;) {
255 
256     // Parse a group of connected commands
257 
258     memset(&line,0,sizeof(struct pipeline));
259     start = parse_pipeline(start, &line);
260     if (!line.cmd) break;
261 
262     // Run those commands
263 
264     run_pipeline(&line);
265     llist_traverse(line.cmd, free_cmd);
266   }
267 }
268 
do_prompt(void)269 static void do_prompt(void)
270 {
271   char *prompt = getenv("PS1"), *s, c, cc;
272 
273   if (!prompt) prompt = "\\$ ";
274   while (*prompt) {
275     c = *(prompt++);
276 
277     if (c=='!') {
278       if (*prompt=='!') prompt++;
279       else {
280         printf("%ld", TT.lineno);
281         continue;
282       }
283     } else if (c=='\\') {
284       cc = *(prompt++);
285       if (!cc) goto down;
286 
287       // \nnn \dD{}hHjlstT@AuvVwW!#$
288       // Ignore bash's "nonprintable" hack; query our cursor position instead.
289       if (cc=='[' || cc==']') continue;
290       else if (cc=='$') putchar(getuid() ? '$' : '#');
291       else if (cc=='h' || cc=='H') {
292         *toybuf = 0;
293         gethostname(toybuf, sizeof(toybuf)-1);
294         if (cc=='h' && (s = strchr(toybuf, '.'))) *s = 0;
295         fputs(toybuf, stdout);
296       } else if (cc=='s') fputs(getbasename(*toys.argv), stdout);
297       else {
298         if (!(c = unescape(cc))) {
299           c = '\\';
300           prompt--;
301         }
302 
303         goto down;
304       }
305       continue;
306     }
307 down:
308     putchar(c);
309   }
310 }
311 
sh_main(void)312 void sh_main(void)
313 {
314   FILE *f = 0;
315 
316   // Set up signal handlers and grab control of this tty.
317   if (isatty(0)) toys.optflags |= FLAG_i;
318 
319   if (*toys.optargs) f = xfopen(*toys.optargs, "r");
320   if (TT.command) handle(xstrdup(TT.command));
321   else {
322     size_t cmdlen = 0;
323     for (;;) {
324       char *command = 0;
325 
326       // TODO: parse escapes in prompt
327       if (!f) do_prompt();
328       if (1 > getline(&command, &cmdlen, f ? f : stdin)) break;
329       handle(command);
330       free(command);
331     }
332   }
333 
334   toys.exitval = 1;
335 }
336