bcb25537d0
function old new delta bltins 252 276 +24 builtin_continue - 12 +12 builtin_break - 12 +12 static.version_str 18 17 -1 run_list 1984 1948 -36 ------------------------------------------------------------------------------ (add/remove: 2/0 grow/shrink: 1/2 up/down: 48/-27) Total: 11 bytes
144 lines
5.1 KiB
Plaintext
144 lines
5.1 KiB
Plaintext
2008-07-14
|
|
|
|
Command parsing
|
|
|
|
Command parsing results in a list of "pipe" structures.
|
|
This list correspond not only to usual "pipe1 || pipe2 && pipe3"
|
|
lists, but it also controls execution of if, while, etc statements.
|
|
Every such statement is a list for hush. List consists of pipes.
|
|
|
|
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 group.
|
|
|
|
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=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
|
|
|
|
Above you see that if is a list, and it sits in a {} group
|
|
implicitly created by hush. Also note two THEN res_word's -
|
|
it is explained below.
|
|
|
|
"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=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.
|
|
|
|
"for" and "case" statements (ab)use progs[] to keep their data
|
|
instead of argv vector progs[] usually do. "for" keyword is forcing
|
|
pipe termination after first word, which makes hush see
|
|
"for v in..." as "for v; in...". "case" keyword does the same.
|
|
Other judiciuosly placed hacks make hush see
|
|
"case word in a) cmd1;; b) cmd2;; esac" as if it was
|
|
"case word; match a; cmd; match b; cmd2; esac"
|
|
("match" is a fictitious keyword here):
|
|
|
|
"case word in a) cmd1;; b) cmd2; esac" -
|
|
pipe 0 res_word=NONE followup=1 SEQ
|
|
prog 0 group {}:
|
|
pipe 0 res_word=CASE followup=SEQ prog[0] 'word'
|
|
pipe 1 res_word=MATCH followup=SEQ prog[0] 'a'
|
|
pipe 2 res_word=CASEI followup=SEQ prog[0] 'cmd1'
|
|
pipe 3 res_word=MATCH followup=SEQ prog[0] 'b'
|
|
pipe 4 res_word=CASEI followup=SEQ prog[0] 'cmd2'
|
|
pipe 5 res_word=CASEI followup=SEQ prog[0] 'cmd3'
|
|
pipe 6 res_word=ESAC followup=SEQ
|
|
pipe 7 res_word=NONE followup=(null)
|
|
pipe 1 res_word=NONE followup=SEQ
|
|
|
|
|
|
2008-01
|
|
|
|
Command execution
|
|
|
|
/* callsite: process_command_subs */
|
|
generate_stream_from_list(struct pipe *head) - handles `cmds`
|
|
create UNIX pipe
|
|
[v]fork
|
|
child:
|
|
redirect pipe output to stdout
|
|
_exit(run_list(head)); /* leaks memory */
|
|
parent:
|
|
return UNIX pipe's output fd
|
|
/* head is freed by the caller */
|
|
|
|
/* callsite: parse_and_run_stream */
|
|
run_and_free_list(struct pipe *)
|
|
run_list(struct pipe *)
|
|
free_pipe_list(struct pipe *)
|
|
|
|
/* callsites: generate_stream_from_list, run_and_free_list, pseudo_exec, run_pipe */
|
|
run_list(struct pipe *) - handles "cmd; cmd2 && cmd3", while/for/do loops
|
|
run_pipe - for every pipe in list
|
|
|
|
/* callsite: run_list */
|
|
run_pipe - runs "cmd1 | cmd2 | cmd3 [&]"
|
|
run_list - used if only one cmd and it is of the form "{cmds;}"
|
|
forks for every cmd if more than one cmd or if & is there
|
|
pseudo_exec - runs each "cmdN" (handles builtins etc)
|
|
|
|
/* callsite: run_pipe */
|
|
pseudo_exec - runs "cmd" (handles builtins etc)
|
|
exec - execs external programs
|
|
run_list - used if cmdN is "(cmds)" or "{cmds;}"
|
|
/* problem: putenv's malloced strings into environ -
|
|
** with vfork they will leak into parent process
|
|
*/
|
|
/* problem with ENABLE_FEATURE_SH_STANDALONE:
|
|
** run_applet_no_and_exit(a, argv) uses exit - this can interfere
|
|
** with vfork - switch to _exit there?
|
|
*/
|