summaryrefslogtreecommitdiff
path: root/shell/hush_doc.txt
diff options
context:
space:
mode:
authorDenis Vlasenko2008-02-10 12:10:08 +0000
committerDenis Vlasenko2008-02-10 12:10:08 +0000
commit05743d79496cf96e9f6f645b6bbc165d51e6aa5c (patch)
tree50fb492810d898cdcafe63009bbb08a1dde039ca /shell/hush_doc.txt
parent68e8e96d7fba018b5b2354434fe0ae95fdfffc4f (diff)
downloadbusybox-05743d79496cf96e9f6f645b6bbc165d51e6aa5c.zip
busybox-05743d79496cf96e9f6f645b6bbc165d51e6aa5c.tar.gz
hush: reinstate `cmd` handling for NOMMU (with fat big warning).
hush: fix a case where none of pipe members could be started because of fork failure hush: rename functions: xxx_real -> xxx hush: try to add a bit more of vfork-friendliness hush: add rudimentary design docs hush: add TODO (newly discovered bug with globbing)
Diffstat (limited to 'shell/hush_doc.txt')
-rw-r--r--shell/hush_doc.txt39
1 files changed, 39 insertions, 0 deletions
diff --git a/shell/hush_doc.txt b/shell/hush_doc.txt
new file mode 100644
index 0000000..a3ead59
--- /dev/null
+++ b/shell/hush_doc.txt
@@ -0,0 +1,39 @@
+ This is how hush runs commands:
+
+/* 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 "{ cmd4; cmd5 && cmd6; }"
+ forks for every cmd if more than one cmd or if & is there
+ pseudo_exec - runs each "cmdN" (handles builtins etc)
+
+/* callsite: run_pipe_real */
+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?
+ */