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| author | Denis Vlasenko <vda.linux@googlemail.com> | 2008-07-14 06:29:38 +0000 |
|---|---|---|
| committer | Denis Vlasenko <vda.linux@googlemail.com> | 2008-07-14 06:29:38 +0000 |
| commit | 395ae452165a607c6b5bc4623225516044619616 (patch) | |
| tree | 00ceff4dcd3fc4604d9252003cf45dfb6cfbedc1 /shell/hush_doc.txt | |
| parent | 17f02e79f407ff2311255981c191a1bf8b3a7ae0 (diff) | |
| download | busybox-w32-395ae452165a607c6b5bc4623225516044619616.tar.gz busybox-w32-395ae452165a607c6b5bc4623225516044619616.tar.bz2 busybox-w32-395ae452165a607c6b5bc4623225516044619616.zip | |
hush: delete unused field in struct child.
reinstate needed check for invalid syntax.
document command parsing in hush_doc.txt.
Diffstat (limited to 'shell/hush_doc.txt')
| -rw-r--r-- | shell/hush_doc.txt | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/shell/hush_doc.txt b/shell/hush_doc.txt index 973fe44c5..ec5dd00f2 100644 --- a/shell/hush_doc.txt +++ b/shell/hush_doc.txt | |||
| @@ -1,3 +1,80 @@ | |||
| 1 | 2008-07-14 | ||
| 2 | |||
| 3 | Command parsing | ||
| 4 | |||
| 5 | Command parsing results in "pipe" structures. "Pipe" structure | ||
| 6 | does not always correspond to what sh language calls "pipe", | ||
| 7 | it also controls execution of if, while, etc statements. | ||
| 8 | |||
| 9 | struct pipe fields: | ||
| 10 | smallint res_word - "none" for normal commands, | ||
| 11 | "if" for if condition etc | ||
| 12 | struct child_prog progs[] - array of commands in pipe | ||
| 13 | smallint followup - how this pipe is related to next: is it | ||
| 14 | "pipe; pipe", "pipe & pipe" "pipe && pipe", | ||
| 15 | "pipe || pipe"? | ||
| 16 | |||
| 17 | Blocks of commands { pipe; pipe; } and (pipe; pipe) are represented | ||
| 18 | as one pipe struct with one progs[0] element which is a "group" - | ||
| 19 | struct child_prog can contain a list of pipes. Sometimes these | ||
| 20 | "groups" are created implicitly, e.g. every control | ||
| 21 | statement (if, while, etc) sits inside its own "pipe" struct). | ||
| 22 | |||
| 23 | res_word controls statement execution. Examples: | ||
| 24 | |||
| 25 | "echo Hello" - | ||
| 26 | pipe 0 res_word=NONE followup=SEQ prog[0] 'echo' 'Hello' | ||
| 27 | pipe 1 res_word=NONE followup=1 SEQ | ||
| 28 | |||
| 29 | "echo foo || echo bar" - | ||
| 30 | pipe 0 res_word=NONE followup=OR prog[0] 'echo' 'foo' | ||
| 31 | pipe 1 res_word=NONE followup=SEQ prog[0] 'echo' 'bar' | ||
| 32 | pipe 2 res_word=NONE followup=SEQ | ||
| 33 | |||
| 34 | "if true; then echo Hello; true; fi" - | ||
| 35 | res_word=NONE followup=SEQ | ||
| 36 | prog 0 group {}: | ||
| 37 | pipe 0 res_word=IF followup=SEQ prog[0] 'true' | ||
| 38 | pipe 1 res_word=THEN followup=SEQ prog[0] 'echo' 'Hello' | ||
| 39 | pipe 2 res_word=THEN followup=SEQ prog[0] 'true' | ||
| 40 | pipe 3 res_word=FI followup=SEQ | ||
| 41 | pipe 4 res_word=NONE followup=(null) | ||
| 42 | pipe 1 res_word=NONE followup=SEQ | ||
| 43 | |||
| 44 | "if true; then { echo Hello; true; }; fi" - | ||
| 45 | pipe 0 res_word=NONE followup=SEQ | ||
| 46 | prog 0 group {}: | ||
| 47 | pipe 0 res_word=IF followup=SEQ prog[0] 'true' | ||
| 48 | pipe 1 res_word=THEN followup=SEQ | ||
| 49 | prog 0 group {}: | ||
| 50 | pipe 0 res_word=NONE followup=SEQ prog[0] 'echo' 'Hello' | ||
| 51 | pipe 1 res_word=NONE followup=SEQ prog[0] 'true' | ||
| 52 | pipe 2 res_word=NONE followup=SEQ | ||
| 53 | pipe 2 res_word=NONE followup=(null) | ||
| 54 | pipe 1 res_word=NONE followup=1 SEQ | ||
| 55 | |||
| 56 | "for v in a b; do echo $v; true; done" - | ||
| 57 | pipe 0 res_word=NONE followup=SEQ | ||
| 58 | prog 0 group {}: | ||
| 59 | pipe 0 res_word=FOR followup=SEQ prog[0] 'v' | ||
| 60 | pipe 1 res_word=IN followup=SEQ prog[0] 'a' 'b' | ||
| 61 | pipe 2 res_word=DO followup=SEQ prog[0] 'echo' '$v' | ||
| 62 | pipe 3 res_word=DO followup=SEQ prog[0] 'true' | ||
| 63 | pipe 4 res_word=DONE followup=SEQ | ||
| 64 | pipe 5 res_word=NONE followup=(null) | ||
| 65 | pipe 1 res_word=NONE followup=SEQ | ||
| 66 | |||
| 67 | Note how "THEN" and "DO" does not just mark the first pipe, | ||
| 68 | it "sticks" to all pipes in the body. This is used when | ||
| 69 | hush executes parsed pipes. | ||
| 70 | |||
| 71 | Dummy trailing pipes with no commands are artifacts of imperfect | ||
| 72 | parsing algorithm - done_pipe() appends new pipe struct beforehand | ||
| 73 | and last one ends up empty and unused. | ||
| 74 | |||
| 75 | |||
| 76 | 2008-01 | ||
| 77 | |||
| 1 | This is how hush runs commands: | 78 | This is how hush runs commands: |
| 2 | 79 | ||
| 3 | /* callsite: process_command_subs */ | 80 | /* callsite: process_command_subs */ |