diff options
| -rw-r--r-- | shell/hush.c | 34 | ||||
| -rw-r--r-- | shell/hush_doc.txt | 77 |
2 files changed, 95 insertions, 16 deletions
diff --git a/shell/hush.c b/shell/hush.c index 47e53f8..db60801 100644 --- a/shell/hush.c +++ b/shell/hush.c @@ -322,7 +322,6 @@ struct child_prog { char **argv; /* program name and arguments */ struct pipe *group; /* if non-NULL, first in group or subshell */ struct redir_struct *redirects; /* I/O redirections */ - struct pipe *family; /* pointer back to the child's parent pipe */ }; /* argv vector may contain variable references (^Cvar^C, ^C0^C etc) * and on execution these are substituted with their values. @@ -2830,7 +2829,6 @@ static void initialize_context(struct p_context *ctx) ctx->pipe = ctx->list_head = new_pipe(); /* Create the memory for child, roughly: * ctx->pipe->progs = new struct child_prog; - * ctx->pipe->progs[0].family = ctx->pipe; * ctx->child = &ctx->pipe->progs[0]; */ done_command(ctx); @@ -2960,6 +2958,7 @@ static int done_word(o_string *word, struct p_context *ctx) { struct child_prog *child = ctx->child; + debug_printf_parse("done_word entered: '%s' %p\n", word->data, child); /* If this word wasn't an assignment, next ones definitely * can't be assignments. Even if they look like ones. */ if (word->o_assignment != DEFINITELY_ASSIGNMENT) { @@ -2967,8 +2966,6 @@ static int done_word(o_string *word, struct p_context *ctx) } else { word->o_assignment = MAYBE_ASSIGNMENT; } - - debug_printf_parse("done_word entered: '%s' %p\n", word->data, child); if (word->length == 0 && word->nonnull == 0) { debug_printf_parse("done_word return 0: true null, ignored\n"); return 0; @@ -2980,15 +2977,17 @@ static int done_word(o_string *word, struct p_context *ctx) word->o_assignment = NOT_ASSIGNMENT; debug_printf("word stored in rd_filename: '%s'\n", word->data); } else { -// if (child->group) { /* TODO: example how to trigger? */ -// syntax(NULL); -// debug_printf_parse("done_word return 1: syntax error, groups and arglists don't mix\n"); -// return 1; -// } + /* "{ echo foo; } echo bar" - bad */ + /* NB: bash allows e.g. "if true; then { echo foo; } fi". TODO? */ + if (child->group) { + syntax(NULL); + debug_printf_parse("done_word return 1: syntax error, groups and arglists don't mix\n"); + return 1; + } #if HAS_KEYWORDS #if ENABLE_HUSH_CASE if (ctx->ctx_dsemicolon) { - /* already done when ctx_dsemicolon was set to 1 */ + /* already done when ctx_dsemicolon was set to 1: */ /* ctx->ctx_res_w = RES_MATCH; */ ctx->ctx_dsemicolon = 0; } else @@ -3085,9 +3084,7 @@ static int done_command(struct p_context *ctx) * child structure is not counted in pi->num_progs. */ pi->progs = xrealloc(pi->progs, sizeof(*pi->progs) * (pi->num_progs+1)); child = &pi->progs[pi->num_progs]; - memset(child, 0, sizeof(*child)); - child->family = pi; ctx->child = child; /* but ctx->pipe and ctx->list_head remain unchanged */ @@ -3100,22 +3097,28 @@ static void done_pipe(struct p_context *ctx, pipe_style type) int not_null; debug_printf_parse("done_pipe entered, followup %d\n", type); - not_null = done_command(ctx); /* implicit closure of previous command */ + /* Close previous command */ + not_null = done_command(ctx); ctx->pipe->followup = type; IF_HAS_KEYWORDS(ctx->pipe->pi_inverted = ctx->ctx_inverted;) IF_HAS_KEYWORDS(ctx->ctx_inverted = 0;) IF_HAS_KEYWORDS(ctx->pipe->res_word = ctx->ctx_res_w;) + /* Without this check, even just <enter> on command line generates * tree of three NOPs (!). Which is harmless but annoying. * IOW: it is safe to do it unconditionally. * RES_NONE case is for "for a in; do ..." (empty IN set) * to work, possibly other cases too. */ if (not_null IF_HAS_KEYWORDS(|| ctx->ctx_res_w != RES_NONE)) { - struct pipe *new_p = new_pipe(); + struct pipe *new_p; + debug_printf_parse("done_pipe: adding new pipe: " + " not_null:%d ctx->ctx_res_w:%d\n", + not_null, ctx->ctx_res_w); + new_p = new_pipe(); ctx->pipe->next = new_p; ctx->pipe = new_p; ctx->child = NULL; /* needed! */ - /* RES_IF, RES_WHILE etc are "sticky" - + /* RES_THEN, RES_DO etc are "sticky" - * they remain set for commands inside if/while. * This is used to control execution. * RES_FOR and RES_IN are NOT sticky (needed to support @@ -3132,7 +3135,6 @@ static void done_pipe(struct p_context *ctx, pipe_style type) #endif /* Create the memory for child, roughly: * ctx->pipe->progs = new struct child_prog; - * ctx->pipe->progs[0].family = ctx->pipe; * ctx->child = &ctx->pipe->progs[0]; */ done_command(ctx); diff --git a/shell/hush_doc.txt b/shell/hush_doc.txt index 973fe44..ec5dd00 100644 --- a/shell/hush_doc.txt +++ b/shell/hush_doc.txt @@ -1,3 +1,80 @@ +2008-07-14 + + Command parsing + +Command parsing results in "pipe" structures. "Pipe" structure +does not always correspond to what sh language calls "pipe", +it also controls execution of if, while, etc statements. + +struct pipe fields: + smallint res_word - "none" for normal commands, + "if" for if condition etc + struct child_prog progs[] - array of commands in pipe + smallint followup - how this pipe is related to next: is it + "pipe; pipe", "pipe & pipe" "pipe && pipe", + "pipe || pipe"? + +Blocks of commands { pipe; pipe; } and (pipe; pipe) are represented +as one pipe struct with one progs[0] element which is a "group" - +struct child_prog can contain a list of pipes. Sometimes these +"groups" are created implicitly, e.g. every control +statement (if, while, etc) sits inside its own "pipe" struct). + +res_word controls statement execution. Examples: + +"echo Hello" - +pipe 0 res_word=NONE followup=SEQ prog[0] 'echo' 'Hello' +pipe 1 res_word=NONE followup=1 SEQ + +"echo foo || echo bar" - +pipe 0 res_word=NONE followup=OR prog[0] 'echo' 'foo' +pipe 1 res_word=NONE followup=SEQ prog[0] 'echo' 'bar' +pipe 2 res_word=NONE followup=SEQ + +"if true; then echo Hello; true; fi" - +res_word=NONE followup=SEQ + prog 0 group {}: + pipe 0 res_word=IF followup=SEQ prog[0] 'true' + pipe 1 res_word=THEN followup=SEQ prog[0] 'echo' 'Hello' + pipe 2 res_word=THEN followup=SEQ prog[0] 'true' + pipe 3 res_word=FI followup=SEQ + pipe 4 res_word=NONE followup=(null) +pipe 1 res_word=NONE followup=SEQ + +"if true; then { echo Hello; true; }; fi" - +pipe 0 res_word=NONE followup=SEQ + prog 0 group {}: + pipe 0 res_word=IF followup=SEQ prog[0] 'true' + pipe 1 res_word=THEN followup=SEQ + prog 0 group {}: + pipe 0 res_word=NONE followup=SEQ prog[0] 'echo' 'Hello' + pipe 1 res_word=NONE followup=SEQ prog[0] 'true' + pipe 2 res_word=NONE followup=SEQ + pipe 2 res_word=NONE followup=(null) +pipe 1 res_word=NONE followup=1 SEQ + +"for v in a b; do echo $v; true; done" - +pipe 0 res_word=NONE followup=SEQ + prog 0 group {}: + pipe 0 res_word=FOR followup=SEQ prog[0] 'v' + pipe 1 res_word=IN followup=SEQ prog[0] 'a' 'b' + pipe 2 res_word=DO followup=SEQ prog[0] 'echo' '$v' + pipe 3 res_word=DO followup=SEQ prog[0] 'true' + pipe 4 res_word=DONE followup=SEQ + pipe 5 res_word=NONE followup=(null) +pipe 1 res_word=NONE followup=SEQ + +Note how "THEN" and "DO" does not just mark the first pipe, +it "sticks" to all pipes in the body. This is used when +hush executes parsed pipes. + +Dummy trailing pipes with no commands are artifacts of imperfect +parsing algorithm - done_pipe() appends new pipe struct beforehand +and last one ends up empty and unused. + + +2008-01 + This is how hush runs commands: /* callsite: process_command_subs */ |