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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?
*/
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