export LFS=/my/soft/mylfs
tar xvf $LFS/sources/bash-3.2.tar.gz -C $LFS/sources/
cd $LFS/sources/bash-3.2/
patch -Np1 -i ../bash-3.2-fixes-5.patch
./configure --prefix=$LFS/builds --without-bash-malloc
make
make install
在读取命令之前执行一些命令，如PS1的打印
bash [C/C++ Application]
bash [9867] [cores: 0]
Thread #1 9867 [core: 0] (Suspended : Step)
execute_builtin_or_function() at execute_cmd.c:3,562 0x42bf86
execute_simple_command() at execute_cmd.c:3,019 0x42bf86
execute_command_internal() at execute_cmd.c:672 0x42952e
parse_and_execute() at evalstring.c:275 0x45dc63
execute_variable_command() at parse.y:2,159 0x41e157
parse_command() at eval.c:215 0x41b1c2
read_command() at eval.c:266 0x41b2a6
reader_loop() at eval.c:132 0x41b4e4
main() at shell.c:715 0x41ac53
gdb (7.2)
执行用户输入命令的堆栈
bash [C/C++ Application]
bash [2689] [cores: 0]
Thread #1 2689 [core: 0] (Suspended : Step)
cd_builtin() at cd.def:163 0x45a830
execute_builtin() at execute_cmd.c:3,153 0x4283d1
execute_builtin_or_function() at execute_cmd.c:3,539 0x42bf60
execute_simple_command() at execute_cmd.c:3,019 0x42bf60
execute_command_internal() at execute_cmd.c:672 0x42952e
execute_command() at execute_cmd.c:352 0x429ffe
reader_loop() at eval.c:147 0x41b412
main() at shell.c:715 0x41ac53
gdb (7.2)
execute_builtin_or_function 方法有一个分支，分为执行内建命令和执行函数
if (builtin)
result = execute_builtin (builtin, words, flags, 0);
else
result = execute_function (var, words, flags, fds_to_close, 0, 0);
如果是执行函数，如何找到执行的函数呢？
func = find_function (words->word->word);
/* Return the pointer to the function implementing builtin command NAME. */
sh_builtin_func_t *
find_shell_builtin (name)
char *name;
{
current_builtin = builtin_address_internal (name, 0);
return (current_builtin ? current_builtin->function : (sh_builtin_func_t *)NULL);
}
static int
execute_builtin (builtin, words, flags, subshell)
sh_builtin_func_t *builtin;
WORD_LIST *words;
int flags, subshell;
{
int old_e_flag, result, eval_unwind;
int isbltinenv;
old_e_flag = exit_immediately_on_error;
/* The eval builtin calls parse_and_execute, which does not know about
the setting of flags, and always calls the execution functions with
flags that will exit the shell on an error if -e is set. If the
eval builtin is being called, and we're supposed to ignore the exit
value of the command, we turn the -e flag off ourselves, then
restore it when the command completes. */
if (subshell == 0 && builtin == eval_builtin && (flags & CMD_IGNORE_RETURN))
{
begin_unwind_frame ("eval_builtin");
unwind_protect_int (exit_immediately_on_error);
exit_immediately_on_error = 0;
eval_unwind = 1;
}
else
eval_unwind = 0;
/* The temporary environment for a builtin is supposed to apply to
all commands executed by that builtin. Currently, this is a
problem only with the `unset', `source' and `eval' builtins. */
isbltinenv = (builtin == source_builtin || builtin == eval_builtin || builtin == unset_builtin);
if (isbltinenv)
{
if (subshell == 0)
begin_unwind_frame ("builtin_env");
if (temporary_env)
{
push_scope (VC_BLTNENV, temporary_env);
if (subshell == 0)
add_unwind_protect (pop_scope, (flags & CMD_COMMAND_BUILTIN) ? 0 : "1");
temporary_env = (HASH_TABLE *)NULL;
}
}
/* `return' does a longjmp() back to a saved environment in execute_function.
If a variable assignment list preceded the command, and the shell is
running in POSIX mode, we need to merge that into the shell_variables
table, since `return' is a POSIX special builtin. */
if (posixly_correct && subshell == 0 && builtin == return_builtin && temporary_env)
{
begin_unwind_frame ("return_temp_env");
add_unwind_protect (merge_temporary_env, (char *)NULL);
}
/*
执行执行的语句，会调用不同的内置方法执行具体的命令，如cd命令会执行cd.def中的cd_builtin方法，内置方法的文件都在builtins目录下
*/
result = ((*builtin) (words->next));
/* This shouldn't happen, but in case `return' comes back instead of
longjmp'ing, we need to unwind. */
if (posixly_correct && subshell == 0 && builtin == return_builtin && temporary_env)
discard_unwind_frame ("return_temp_env");
if (subshell == 0 && isbltinenv)
run_unwind_frame ("builtin_env");
if (eval_unwind)
{
exit_immediately_on_error += old_e_flag;
discard_unwind_frame ("eval_builtin");
}
return (result);
}