Introduction to strip commands in Linux------undress files

1, remove-g, equal to the program to do the--strip-debug
2, strip program, equal to the program did--strip-debug and--strip-symbol

As a Linux developer, if you have not heard of the strip command, it is very inappropriate. Strip this word, everyone should have learned, you remember to take off clothes on the line, other don't think much. In Linux, strip also has the meaning of undressing, specifically to remove some of the symbolic information and debugging information from certain files.

Let's look at the Main.c file:

[CPP]View PlainCopy 

2. #include <stdio.h>
6. int add (int x, int y)
8. {
10. return x + y;
12. }
16. int AAA;
18. int BBB = 1;
20. Char sztest[] = "good";
24. int main ()
26. {
28. int CCC = 2;
30. return 0;
32. }

Then we look at the results:

[Plain]View PlainCopy 

2. [[email protected] learn_strip]$ ls
4. Main.c
6. [Email protected] learn_strip]$ gcc main.c
8. [Email protected] learn_strip]$ ls-l a.out
10. -rwxrwxr-x 1 taoge taoge 4673 Jul 05:30 a.out
12. [[Email protected] learn_strip]$ file a.out
14. A.out:elf 32-bit LSB executable, Intel 80386, version 1 (gnu/linux), dynamically linked (uses shared libs), for Gnu/linux 2.6.18, not stripped
16. [Email protected] learn_strip]$ nm a.out
18. 08049538 D _dynamic
20. 08049604 D _global_offset_table_
22. 0804847c R _io_stdin_used
24. W _jv_registerclasses
26. 08049528 D __ctor_end__
28. 08049524 D __ctor_list__
30. 08049530 D __dtor_end__
32. 0804952C D __dtor_list__
34. 08048520 R __frame_end__
36. 08049534 D __jcr_end__
38. 08049534 D __jcr_list__
40. 08049628 A __bss_start
42. 08049618 D __data_start
44. 08048430 T __do_global_ctors_aux
46. 08048310 T __do_global_dtors_aux
48. 08048480 R __dso_handle
50. W __gmon_start__
52. 0804842a T __I686.GET_PC_THUNK.BX
54. 08049524 D __init_array_end
56. 08049524 D __init_array_start
58. 080483C0 T __libc_csu_fini
60. 080483d0 T __libc_csu_init
62. U [email protected] @GLIBC_2.0
64. 08049628 A _edata
66. 08049634 A _end
68. 0804845C T _fini
70. 08048478 R _FP_HW
72. 08048274 T _init
74. 080482E0 T _start
76. 08049630 B AAA
78. 08048394 T Add
80. 0804961c D BBB
82. 08049628 b completed.5963
84. 08049618 W Data_start
86. 0804962C b dtor_idx.5965
88. 08048370 T Frame_dummy
90. 080483A2 T Main
92. 08049620 D Sztest
94. [Email protected] learn_strip]$

The Ls-l command indicates that the size of the a.out is 4,673 bytes;

The file command shows that A.out is an executable and not stripped, that is, no undressing.

With the NM command, you can read the symbolic information in the a.out.

Now, I strip A.out's clothes off and get the result:

[Plain]View PlainCopy 

2. [[email protected] learn_strip]$ ls
4. A.out MAIN.C
6. [email protected] learn_strip]$ strip a.out
8. [Email protected] learn_strip]$ ls-l a.out
10. -rwxrwxr-x 1 taoge taoge 2980 Jul 05:34 a.out
12. [[Email protected] learn_strip]$ file a.out
14. A.out:elf 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for Gnu/linux 2.6. Stripped,
16. [Email protected] learn_strip]$ nm a.out
18. Nm:a.out:no symbols
20. [Email protected] learn_strip]$

The Ls-l command indicates that the size of the a.out is 2,980 bytes, greatly reduced;

Through the file command, A.out is an executable file, and it is stripped, that is, the clothes are taken off;

Through the NM command, it was found that the symbols in the a.out were gone.

This shows that strip used to take off the files of the clothes, the file will be smaller, where the symbolic information will be lost. What's the use of this strip? That's very useful! The original a.out is larger and can be executed. After the strip, the file becomes smaller and can still be executed, which saves a lot of space.

In fact, strip can be used not only for executables, but also for target files and dynamic libraries.

In the actual development, it is often necessary to strip the dynamic library. So to reduce floor space. And when debugging (for example, with Addr2line), you need symbols. Therefore, the usual practice is: Strip before the library for debugging, strip after the library for the actual release, they have a correspondence between the two. Once the published strip library is out of the question, you can find the corresponding non-strip library to locate.

Finally, a dynamic library strip is about 18M ago, after strip is about 3M, visible, undress or have obvious advantages.

Add: Later found that in the debugging process, often involved in the library, the library is too large, very expensive transmission time, so still use strip to do it.

Introduction to strip commands in Linux------undress files