bash 源码分析
- 下载解压 bash-3.2
- 编译bash
- export LFS=/my/soft/mylfs
- tar xvf $LFS/sources/bash-3.2.tar.gz -C $LFS/sources/
- cd $LFS/sources/bash-3.2/
- patch -Np1 -i ../bash-3.2-fixes-.patch
- ./configure --prefix=$LFS/builds --without-bash-malloc
- make
- make install
- 常用的调用堆栈
- 在读取命令之前执行一些命令,如PS1的打印
- bash [C/C++ Application]
- bash [] [cores: ]
- Thread # [core: ] (Suspended : Step)
- execute_builtin_or_function() at execute_cmd.c:, 0x42bf86
- execute_simple_command() at execute_cmd.c:, 0x42bf86
- execute_command_internal() at execute_cmd.c: 0x42952e
- parse_and_execute() at evalstring.c: 0x45dc63
- execute_variable_command() at parse.y:, 0x41e157
- parse_command() at eval.c: 0x41b1c2
- read_command() at eval.c: 0x41b2a6
- reader_loop() at eval.c: 0x41b4e4
- main() at shell.c: 0x41ac53
- gdb (7.2)
- 执行用户输入命令的堆栈
- bash [C/C++ Application]
- bash [] [cores: ]
- Thread # [core: ] (Suspended : Step)
- cd_builtin() at cd.def: 0x45a830
- execute_builtin() at execute_cmd.c:, 0x4283d1
- execute_builtin_or_function() at execute_cmd.c:, 0x42bf60
- execute_simple_command() at execute_cmd.c:, 0x42bf60
- execute_command_internal() at execute_cmd.c: 0x42952e
- execute_command() at execute_cmd.c: 0x429ffe
- reader_loop() at eval.c: 0x41b412
- main() at shell.c: 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, );
- else
- result = execute_function (var, words, flags, fds_to_close, , );
- 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, );
- return (current_builtin ? current_builtin->function : (sh_builtin_func_t *)NULL);
- }
- 执行内置命令的方法如下:
- 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 == && builtin == eval_builtin && (flags & CMD_IGNORE_RETURN))
- {
- begin_unwind_frame ("eval_builtin");
- unwind_protect_int (exit_immediately_on_error);
- exit_immediately_on_error = ;
- eval_unwind = ;
- }
- else
- eval_unwind = ;
- /* 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 == )
- begin_unwind_frame ("builtin_env");
- if (temporary_env)
- {
- push_scope (VC_BLTNENV, temporary_env);
- if (subshell == )
- add_unwind_protect (pop_scope, (flags & CMD_COMMAND_BUILTIN) ? : "");
- 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 == && 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 == && builtin == return_builtin && temporary_env)
- discard_unwind_frame ("return_temp_env");
- if (subshell == && isbltinenv)
- run_unwind_frame ("builtin_env");
- if (eval_unwind)
- {
- exit_immediately_on_error += old_e_flag;
- discard_unwind_frame ("eval_builtin");
- }
- return (result);
- }
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