执行 asm 程序后不要在 shell 换行。 [美国电话电报公司]

Question

如标题所说，asm 程序执行后不应自动换行。我的程序是 linux 中 "echo" 命令的简化版本。它打印用户给出的参数。如果用户的第一个参数是“-n”，提示符应该在输出的右边，而不是换行。所以我的问题是如何在执行后强制不在 AT&T 中断行？

.code32
.section .data
    lf: .ascii "-n"             # Lf = line feed
    withoutLF: .long 0             # helper flag
    counter: .long 0            # is the counter of bytes of an argument
    arguments: .long 0          # number of arguments
    white_space: .ascii " "     # is white space

.section .text

.globl _start

_start:
    movl (%esp), %esi           # gets the argument count of the stack to ESI
    movl %esi, arguments        # moves argument count to arguments variable
    decl arguments              # decrement counter
    addl , %esp               # move the esp to the actual arguments

    ### check if first argument is '-n' ###

    movl (%esp), %esi           # move first string to ESI
    movl $lf, %edi              # move second string to EDI
    movl , %ecx               # number of  bytes which should be compared
    cld                         # clear Flag D, wihtout clearance the compare ill occur in inverse order 
    rep cmpsb                   # the actual comparing of the 2 strings
    jz _without_lf              # if the same jump to _without_lf

_arg:
    movl (%esp), %esi           # moves argument of stack to ESI
    cmpl [=11=], arguments          # compares if there any arguments left
    je _exit                    # out of arguments --> exit progamm
    jmp _print_white_space      # if NOT out of arguments --> print a white space


_numberOfBytes:
    lodsb                       # load string in bytes from ESI --> saves byte in EAX
    cmpb [=11=], %al                # compare if byte is equal 0
    je _print_arg               # jumps to section to print the actual argument
    incl counter                # increment the counter (number of bytes)
    jmp _numberOfBytes          # jump to the beginning of _numberOfBytes (to read the left bytes)

_print_arg:
    movl counter, %edx          # EDX message length 
    movl , %ebx               # EBX = file descriptor (1 = stdout)
    movl (%esp), %ecx           # ECX = address of message
    movl , %eax               # syscall number (4 = write)
    int [=11=]x80                   # call kernel by interrupt

    addl , %esp               # move ESP to next argument (1 argument = 4 bytes)
    decl arguments              # decrement the number of arguments
    movl [=11=], counter            # reset the counter of bytes
    jmp _arg                    # jump to the top of _arg

_print_white_space:
    movl , %edx               # EDX message length
    movl , %ebx               # EBX = file descriptor (1 = stdout)
    movl $white_space, %ecx     # ECX = address of message (startaddress)
    movl , %eax               # syscall number (4 = write)
    int [=11=]x80                   # call kernel by interrupt
    jmp _numberOfBytes          # jump to _numberOfBytes --> still arguments left to print

_without_lf:
    addl , %esp               # move ESP to next argument of the stack
    decl arguments              # decrement arguments counter --> '-n' is not counted, just used
    incl withoutLF              # move 1 to withLF (helper flag)
    jmp _arg

   _exit:                       # exit the program
     movl [=11=], %ebx
     movl , %eax
     int [=11=]x80

这是我程序的输出

$PS1、$PS1和普通回显命令的输出：

字节数是单词的 6 个 "Hello" 所以有一个空终止符

Answer 1

您的程序正在运行。

与 zsh 一样，fish 会在程序输出后让您的提示换行，即使它没有以换行结尾。

发生这种情况时，会在行尾留下一个“⏎”。（zsh 留下一个“%”IIRC）

所以那些你能看到“⏎”的时候，你的程序已经没有打印换行符了。但是为了避免程序的输出和 shell 的提示之间的混淆，提示总是换行是很好的，所以使用了这个技巧。

而且 fish 不使用 $PS1 或 $PS2，所以这些都没有用。相反，它使用 fish_prompt 函数。

执行 asm 程序后不要在 shell 换行。 [美国电话电报公司]

Don't line break in shell after executing asm programm. [AT&T]

assembly

att

fish