shell/bbsh.c

   1 /* vi: set ts=4 :
   2  *
   3  * bbsh - busybox shell
   4  *
   5  * Copyright 2006 Rob Landley <rob@landley.net>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   8  */
   9
  10 // A section of code that gets repeatedly or conditionally executed is stored
  11 // as a string and parsed each time it's run.
  12
  13
  14
  15 // Wheee, debugging.
  16
  17 // Terminal control
  18 #define ENABLE_BBSH_TTY        0
  19
  20 // &, fg, bg, jobs.  (ctrl-z with tty.)
  21 #define ENABLE_BBSH_JOBCTL     0
  22
  23 // Flow control (if, while, for, functions { })
  24 #define ENABLE_BBSH_FLOWCTL    0
  25
  26 #define ENABLE_BBSH_ENVVARS    0  // Environment variable support
  27
  28 // Local and synthetic variables, fancy prompts, set, $?, etc.
  29 #define ENABLE_BBSH_LOCALVARS  0
  30
  31 // Pipes and redirects: | > < >> << && || & () ;
  32 #define ENABLE_BBSH_PIPES      0
  33
  34 /* Fun:
  35
  36   echo `echo hello#comment " woot` and more
  37 */
  38
  39 #include "libbb.h"
  40
  41 // A single executable, its arguments, and other information we know about it.
  42 #define BBSH_FLAG_EXIT    1
  43 #define BBSH_FLAG_SUSPEND 2
  44 #define BBSH_FLAG_PIPE    4
  45 #define BBSH_FLAG_AND     8
  46 #define BBSH_FLAG_OR      16
  47 #define BBSH_FLAG_AMP     32
  48 #define BBSH_FLAG_SEMI    64
  49 #define BBSH_FLAG_PAREN   128
  50
  51 // What we know about a single process.
  52 struct command {
  53         struct command *next;
  54         int flags;              // exit, suspend, && ||
  55         int pid;                // pid (or exit code)
  56         int argc;
  57         char *argv[0];
  58 };
  59
  60 // A collection of processes piped into/waiting on each other.
  61 struct pipeline {
  62         struct pipeline *next;
  63         int job_id;
  64         struct command *cmd;
  65         char *cmdline;
  66         int cmdlinelen;
  67 };
  68
  69 static void free_list(void *list, void (*freeit)(void *data))
  70 {
  71         while (list) {
  72                 void **next = (void **)list;
  73                 void *list_next = *next;
  74                 freeit(list);
  75                 free(list);
  76                 list = list_next;
  77         }
  78 }
  79
  80 // Parse one word from the command line, appending one or more argv[] entries
  81 // to struct command.  Handles environment variable substitution and
  82 // substrings.  Returns pointer to next used byte, or NULL if it
  83 // hit an ending token.
  84 static char *parse_word(char *start, struct command **cmd)
  85 {
  86         char *end;
  87
  88         // Detect end of line (and truncate line at comment)
  89         if (ENABLE_BBSH_PIPES && strchr("><&|(;", *start)) return 0;
  90
  91         // Grab next word.  (Add dequote and envvar logic here)
  92         end = start;
  93         end = skip_non_whitespace(end);
  94         (*cmd)->argv[(*cmd)->argc++] = xstrndup(start, end-start);
  95
  96         // Allocate more space if there's no room for NULL terminator.
  97
  98         if (!((*cmd)->argc & 7))
  99                         *cmd = xrealloc(*cmd,
 100                                         sizeof(struct command) + ((*cmd)->argc+8)*sizeof(char *));
 101         (*cmd)->argv[(*cmd)->argc] = 0;
 102         return end;
 103 }
 104
 105 // Parse a line of text into a pipeline.
 106 // Returns a pointer to the next line.
 107
 108 static char *parse_pipeline(char *cmdline, struct pipeline *line)
 109 {
 110         struct command **cmd = &(line->cmd);
 111         char *start = line->cmdline = cmdline;
 112
 113         if (!cmdline) return 0;
 114
 115         if (ENABLE_BBSH_JOBCTL) line->cmdline = cmdline;
 116
 117         // Parse command into argv[]
 118         for (;;) {
 119                 char *end;
 120
 121                 // Skip leading whitespace and detect end of line.
 122                 start = skip_whitespace(start);
 123                 if (!*start || *start=='#') {
 124                         if (ENABLE_BBSH_JOBCTL) line->cmdlinelen = start-cmdline;
 125                         return 0;
 126                 }
 127
 128                 // Allocate next command structure if necessary
 129                 if (!*cmd) *cmd = xzalloc(sizeof(struct command)+8*sizeof(char *));
 130
 131                 // Parse next argument and add the results to argv[]
 132                 end = parse_word(start, cmd);
 133
 134                 // If we hit the end of this command, how did it end?
 135                 if (!end) {
 136                         if (ENABLE_BBSH_PIPES && *start) {
 137                                 if (*start==';') {
 138                                         start++;
 139                                         break;
 140                                 }
 141                                 // handle | & < > >> << || &&
 142                         }
 143                         break;
 144                 }
 145                 start = end;
 146         }
 147
 148         if (ENABLE_BBSH_JOBCTL) line->cmdlinelen = start-cmdline;
 149
 150         return start;
 151 }
 152
 153 // Execute the commands in a pipeline
 154 static int run_pipeline(struct pipeline *line)
 155 {
 156         struct command *cmd = line->cmd;
 157         if (!cmd || !cmd->argc) return 0;
 158
 159         // Handle local commands.  This is totally fake and plastic.
 160         if (cmd->argc==2 && !strcmp(cmd->argv[0],"cd"))
 161                 chdir(cmd->argv[1]);
 162         else if (!strcmp(cmd->argv[0],"exit"))
 163                 exit(cmd->argc>1 ? atoi(cmd->argv[1]) : 0);
 164         else {
 165                 int status;
 166                 pid_t pid=fork();
 167                 if (!pid) {
 168                         run_applet_and_exit(cmd->argv[0],cmd->argc,cmd->argv);
 169                         execvp(cmd->argv[0],cmd->argv);
 170                         printf("No %s",cmd->argv[0]);
 171                         exit(1);
 172                 } else waitpid(pid, &status, 0);
 173         }
 174
 175         return 0;
 176 }
 177
 178 static void free_cmd(void *data)
 179 {
 180         struct command *cmd=(struct command *)data;
 181
 182         while (cmd->argc) free(cmd->argv[--cmd->argc]);
 183 }
 184
 185
 186 static void handle(char *command)
 187 {
 188         struct pipeline line;
 189         char *start = command;
 190
 191         for (;;) {
 192                 memset(&line,0,sizeof(struct pipeline));
 193                 start = parse_pipeline(start, &line);
 194                 if (!line.cmd) break;
 195
 196                 run_pipeline(&line);
 197                 free_list(line.cmd, free_cmd);
 198         }
 199 }
 200
 201 int bbsh_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 202 int bbsh_main(int argc, char **argv)
 203 {
 204         char *command=NULL;
 205         FILE *f;
 206
 207         getopt32(argv, "c:", &command);
 208
 209         f = argv[optind] ? xfopen(argv[optind],"r") : NULL;
 210         if (command) handle(command);
 211         else {
 212                 unsigned cmdlen=0;
 213                 for (;;) {
 214                         if (!f) putchar('$');
 215                         if (1 > getline(&command, &cmdlen,f ? : stdin)) break;
 216
 217                         handle(command);
 218                 }
 219                 if (ENABLE_FEATURE_CLEAN_UP) free(command);
 220         }
 221
 222         return 1;
 223 }