Second drop. More infrastructure in place, especially for parsing pipelines.

The minimal version got a couple hundred bytes bigger, partly because it's
broken into more functions but mostly because it now dynamically reallocates
and frees everything with no hard-coded limits.  (I thought about making
that optional, but there's a limit to what I can debug and maintain.  It
should still be reasonably NOMMU friendly, the allocations are small and
short lived, and shouldn't contribute noticeably to long-term memory
fragmentation.)

diff --git a/shell/bbsh.c b/shell/bbsh.c
index f2d76cc01da2e8e2729fca62818a4df926103916..57a103bf8871a53455cc70db6a40a254e9bf87fd 100644 (file)
--- a/shell/bbsh.c
+++ b/shell/bbsh.c
@@ -7,49 +7,197 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-// Handle embedded NUL bytes in the command line.
+// A section of code that gets repeatedly or conditionally executed is stored
+// as a string and parsed each time it's run.
+
+
+
+// Wheee, debugging.
+
+// Terminal control
+#define ENABLE_BBSH_TTY        0
+
+// &, fg, bg, jobs.  (ctrl-z with tty.)
+#define ENABLE_BBSH_JOBCTL     0
+
+// Flow control (if, while, for, functions { })
+#define ENABLE_BBSH_FLOWCTL    0
+
+#define ENABLE_BBSH_ENVVARS    0  // Environment variable support
+
+// Local and synthetic variables, fancy prompts, set, $?, etc.
+#define ENABLE_BBSH_LOCALVARS  0
+
+// Pipes and redirects: | > < >> << && || & () ;
+#define ENABLE_BBSH_PIPES      0
+
+/* Fun:
+
+  echo `echo hello#comment " woot` and more
+*/
 
 #include <busybox.h>
 
-static int handle(char *command)
+// A single executable, its arguments, and other information we know about it.
+#define BBSH_FLAG_EXIT    1
+#define BBSH_FLAG_SUSPEND 2
+#define BBSH_FLAG_PIPE    4
+#define BBSH_FLAG_AND     8
+#define BBSH_FLAG_OR      16
+#define BBSH_FLAG_AMP     32
+#define BBSH_FLAG_SEMI    64
+#define BBSH_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;
+       int cmdlinelen;
+};
+
+static void free_list(void *list, void (*freeit)(void *data))
+{
+       while(list) {
+               void **next = (void **)list;
+               void *list_next = *next;
+               freeit(list);
+               free(list);
+               list = list_next;
+       }
+}
+
+// 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 (ENABLE_BBSH_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 *pipe)
 {
-       int argc=0;
-       char *argv[10], *start = command;
+       struct command **cmd = &(pipe->cmd);
+       char *start = pipe->cmdline = cmdline;
+
+       if (!cmdline) return 0;
+
+       if (ENABLE_BBSH_JOBCTL) pipe->cmdline = cmdline;
 
        // Parse command into argv[]
        for (;;) {
                char *end;
 
-               // Skip leading whitespace and detect EOL.
-               while(isspace(*start)) start++;
-               if(!*start || *start=='#') break;
+               // Skip leading whitespace and detect end of line.
+               while (isspace(*start)) start++;
+               if (!*start || *start=='#') {
+                       if (ENABLE_BBSH_JOBCTL) pipe->cmdlinelen = start-cmdline;
+                       return 0;
+               }
 
-               // Grab next word.  (Add dequote and envvar logic here)
-               end=start;
-               while(*end && !isspace(*end)) end++;
-               argv[argc++]=xstrndup(start,end-start);
-               start=end;
+               // 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 (ENABLE_BBSH_PIPES && *start) {
+                               if (*start==';') {
+                                       start++;
+                                       break;
+                               }
+                               // handle | & < > >> << || && 
+                       }
+                       break;
+               }
+               start = end;
        }
-       argv[argc]=0;
 
-       if (!argc) return 0;
-       if (argc==2 && !strcmp(argv[0],"cd")) chdir(argv[1]);
-       else if(!strcmp(argv[0],"exit")) exit(argc>1 ? atoi(argv[1]) : 0); 
+       if (ENABLE_BBSH_JOBCTL) pipe->cmdlinelen = start-cmdline;
+
+       return start;
+}
+
+// Execute the commands in a pipeline
+static int run_pipeline(struct pipeline *pipe)
+{
+       struct command *cmd = pipe->cmd;
+       if (!cmd || !cmd->argc) return 0;
+
+       // Handle local commands.  This is totally fake and plastic.
+       if (cmd->argc==2 && !strcmp(cmd->argv[0],"cd"))
+               chdir(cmd->argv[1]);
+       else if(!strcmp(cmd->argv[0],"exit"))
+               exit(cmd->argc>1 ? atoi(cmd->argv[1]) : 0); 
        else {
                int status;
                pid_t pid=fork();
                if(!pid) {
-                       run_applet_by_name(argv[0],argc,argv);
-                       execvp(argv[0],argv);
-                       printf("No %s",argv[0]);
+                       run_applet_by_name(cmd->argv[0],cmd->argc,cmd->argv);
+                       execvp(cmd->argv[0],cmd->argv);
+                       printf("No %s",cmd->argv[0]);
                        exit(1);
                } else waitpid(pid, &status, 0);
        }
-       while(argc) free(argv[--argc]);
 
        return 0;
 }
 
+static void free_cmd(void *data)
+{
+       struct command *cmd=(struct command *)data;
+
+       while(cmd->argc) free(cmd->argv[--cmd->argc]);
+}
+
+
+static void handle(char *command)
+{
+       struct pipeline pipe;
+       char *start = command;
+
+       for (;;) {
+               memset(&pipe,0,sizeof(struct pipeline));
+               start = parse_pipeline(start, &pipe);
+               if (!pipe.cmd) break;
+
+               run_pipeline(&pipe);
+               free_list(pipe.cmd, free_cmd);
+       }
+}
+
 int bbsh_main(int argc, char *argv[])
 {
        char *command=NULL;
@@ -62,8 +210,11 @@ int bbsh_main(int argc, char *argv[])
        else {
                unsigned cmdlen=0;
                for (;;) {
+                       struct pipeline pipe;
+
                        if(!f) putchar('$');
-                       if(1 > getline(&command,&cmdlen,f ? : stdin)) break;
+                       if(1 > getline(&command, &cmdlen,f ? : stdin)) break;
+
                        handle(command);
                }
                if (ENABLE_FEATURE_CLEAN_UP) free(command);