c - 在 C 中的 '\0' 字符后打印新行

Question

我目前正在做一项作业，我们要重新创建 cat 命令的三个开关 -n/-T/-E。我们要编译并输入两个参数:开关和文件名。我将文本文件内容存储到缓冲区中。

int main(int argc, char *argv[]){

int index = 0;
int number = 1;
int fd, n, e, t;
n = e = t = 0;
char command[5];

char buffer[BUFFERSIZE];

strcpy(command, argv[1]);
fd = open(argv[2], O_RDONLY);
if( fd == -1)
{
    perror(argv[2]);
    exit(1);
}

read(fd, buffer,BUFFERSIZE);

if( !strcmp("cat", command)){
    printf("%s\n", buffer);
}
else if( !strcmp("-n", command)){
    n = 1;
}
else if( !strcmp("-E", command)){
    e = 1;
}
else if( !strcmp("-T", command)){
    t = 1;
}
else if( !strcmp("-nE", command) || !strcmp("-En", command)){
    n = e = 1;
}
else if( !strcmp("-nT", command) || !strcmp("-Tn", command)){
    n = t = 1;
}
else if( !strcmp("-ET", command) || !strcmp("-TE", command)){
    t = e = 1;
}
else if( !strcmp("-nET", command) || !strcmp("-nTE", command) || 
      !strcmp("-TnE", command) || !strcmp("-EnT", command) || 
      !strcmp("-ETn", command) || !strcmp("-TEn", command)){
    n = e = t = 1;
}
else{
    printf("Invalid Switch Entry");
}

if(n){
    printf("%d  ", number++); 
}

while(buffer[index++] != '\0' && ( n || e || t)){
    if(buffer[index] == '\n' && e && n){
        printf("$\n%d  ", number++);
    }
    else if(buffer[index] == '\n' && e){
        printf("$\n");
    }
    else if(buffer[index] == '\t' && t){
        printf("^I");
    }
    else if(buffer[index] == '\n' && n){
        printf("\n%d  ", number++);
    }
    else {
        printf("%c", buffer[index]);
    }
}
printf("\n");
close(fd);
return 0;

}

除了当我尝试使用 -n 命令时，一切都很完美。它添加了额外的新行。我使用的文本文件具有

hello

 hello

   hello world! 

而不是

1 hello

2  hello

3    hello world!

它将打印出以下内容:

1 hello

2  hello

3    hello world!

4

出于某种原因，它在世界后面添加了额外的行!

Am I missing something simple?

Answer 1

这可能无法解决您的问题，但我没有看到任何代码将终止空字符放入缓冲区中。尝试:

// Reserve one character for the null terminator.
ssize_t n = read(fd, buffer, BUFFERSIZE-1);
if ( n == -1  )
{
   // Deal with error.
   printf("Unable to read the contents of the file.\n");
   exit(1); //???
}

buffer[n] = '\0';