c++ - C 程序的执行方式与 shell 不同

Question

我试图将此输入作为字符读入 c 中的二维数组内存中。

00P015
00P116
030000
06P0ZZ
030005
06P1ZZ
04P0ZZ
26P1ZZ
3412ZZ
030010
06P0ZZ
99ZZZZ
030010
06P1ZZ
99ZZZZ
ZZ0000
ZZ0010

我的代码是

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


int pr;
int value;
/*These are variables representing the VM itself*/

char IR[6] ;
short int PC = 0 ;

int P0 ;                                                                //these are the pointer registers
int P1 ;
int P2 ;
int P3 ;

int R0 ; //GP regs
int R1 ;
int R2 ;
int R3 ;

int ACC ;
char PSW[2];
char memory [100][6]  ;                                                 //this is the program memory for first program
short int opcode ;                                                      //nice to know what we are doing
int program_line = 0 ;


int fp ;
int i ;
int q = -1;                                                                  //Used to iterate through memory to execute program
int TrueFalse;                                                          //True / False value for check statements, 1 implies true, 0 implies false
int halt = 0;
int address;


char input_line [7] ;

main(int argc, char *argv[])
{                                                                       //Read file into VM
    fp = open("C:\\Users\\Whiskey Golf\\ClionProjects\\untitled\\program.txt", O_RDONLY) ;
    printf("Open is %d\n", fp) ;                                        //always check the return value.

    if (fp < 0)                                                         //error in read
    {printf("Could not open file\n");
        exit(0) ;
    }
                                                                        //read in the first line of the program
    int charRead = read (fp, input_line, 8 ) ;                          //returns number of characters read`
    printf("\n*******************************\n");
    printf("* Reading Program Into Memory *\n");
    printf("*******************************\n");
    while (1)
    { if (charRead <= 0)                                                //indicates end of file or error
            break ;                                                     //breaks out of infinite loop

        for (i = 0; i < 6 ; i++)                                        //If we get here must have correctly read in a line of program code.
            memory[program_line][i] = input_line[i] ;                   //copy from input line into program memory

        printf("Program Line %d: ", program_line) ;                     //printing out program line for debugging purposes
        for(i = 0; i <  6; i++)
            printf("%c", memory[program_line][i]) ;
        printf("\n") ;

        opcode = (memory[program_line][0] -48) *10 ;                    //Get opcode, print out opcode to console
        opcode += (memory[program_line][1] -48) ;

        printf("Opcode is %d\n", opcode) ;

        charRead = read (fp, input_line, 8) ;                           //read in next line of code

        if(input_line[0] == 'Z')                                        //if the firat character is a 'Z' then you are reading data.
            break ;                                                     //No more program code so break out of loop

        program_line++ ;                                                //now at a new line in the prog
        printf("%n");
    }

我遇到的问题是，当我在 IDE 中运行我在 Clion 中编写的程序时，我的输出是正确的，我得到

Program Line 0: 00P015
Opcode is 0
Program Line 1: 00P116
Opcode is 0
Program Line 2: 030000
Opcode is 3
Program Line 3: 06P0ZZ
Opcode is 6

但是当我通过 gcc 编译通过 shell 运行代码然后执行 ./a.out 时，我得到的输出是

Program Line 0: 00P015
Opcode is 0
Program Line 1: 16
Opcode is -528
Program Line 2: 00
Opcode is -528
Program Line 3: ZZ
Opcode is-528

我已经尝试调试这个问题有一段时间了，当我通过 shell 执行此操作时，我无法让它正常工作，而这正是我需要执行的方式。任何帮助将不胜感激。

Answer 1

您正在读取 8 字节，该字节采用行尾字符 '\n' 并尝试将其存储在 7 字节数组中.

read (fp, input_line, 8)

这会导致未定义的行为，它应该是

read(fp, input_line, 7)

然后你可以像这样丢弃下一个字节

char discard; 
read(fp, &discard, 1);

我想您正在读取 8 字节来消耗行尾字符，因此您可以将数组大小增加到 8 并忽略最后一个字符或简单地读取并丢弃它。

编辑:仔细查看数据和代码，我发现我不明白你想要做什么，你必须只读取 7 个字符，将包含尾随 '\n'，当且仅当每行后面始终有一个新行 '\n' 时，以下代码才会起作用，否则它将跳过最后一行，你应该自己想出明显的解决方案。另请参阅this comment ，如果你在MS Windows上用文本编辑器编写程序，你就会遇到麻烦。要解决这个问题，您可以使用 fopen() 而不是低级 I/O。

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

int
main(void)
{
    int file;
    ssize_t length;
    char buffer[7];
    file = open("program.txt", O_RDONLY);
    if (file == -1)
        return -1;
    while ((length = read(file, buffer, sizeof(buffer))) == 0)
    {
        int opcode;
        /* You will need to overwrite the '\n' for the printf() to work 
         * but you can skip this if you don't want to print the command
         */
        buffer[length - 1] = '\0'; 
        opcode = 10 * (buffer[0] - '0') + buffer[1] - '0';
        fprintf(stderr, "Command: `%s'\n\topcode: %d\n", buffer, opcode);
    }
    close(file);
    return 0;
}