Question

我已经读取了/ proc / uptime的值（这是自上次启动以来的秒数），我正在尝试将其转换为：DD：HH：MM：SS。而且我一直收到这个错误：“左值作为赋值的左操作数需要左值： *

这是我的代码：



/**
* Method Retrieves Time Since System Was Last Booted [dd:hh:mm:ss]
*/
int kerstat_get_boot_info(sys_uptime_info *s)
{
    /* Initialize Values To Zero's */
    memset(s, 0, sizeof(sys_uptime_info));

    /* Open File & Test For Failure */
    FILE *fp = fopen("/proc/uptime", "r");
    if(!fp) { return -1; }

    /* Intilaize Variables */
    char buf[256];
    size_t bytes_read;

    /* Read Entire File Into Buffer */
    bytes_read = fread(buf, 1, sizeof(buf), fp);

    /* Close File */
    fclose(fp);

    /* Test If Read Failed Or If Buffer Isn't Big Enough */
    if(bytes_read == 0 || bytes_read == sizeof(buf))
        return -1;

    /* Null Terminate Text */
    buf[bytes_read] = '\0';

    sscanf(buf, "%d", &s->boot_time);

    &s->t_days = s->boot_time/60/60/24;
    &s->t_hours = s->boot_time/60/60%24;
    &s->t_minutes = s->boot_time/60%60;
    &s->t_seconds = s->boot_time%60;
}

/** * Method Retrieves Time Since System Was Last Booted [dd:hh:mm:ss] */ int kerstat_get_boot_info(sys_uptime_info *s) { /* Initialize Values To Zero's */ memset(s, 0, sizeof(sys_uptime_info)); /* Open File & Test For Failure */ FILE *fp = fopen("/proc/uptime", "r"); if(!fp) { return -1; } /* Intilaize Variables */ char buf[256]; size_t bytes_read; /* Read Entire File Into Buffer */ bytes_read = fread(buf, 1, sizeof(buf), fp); /* Close File */ fclose(fp); /* Test If Read Failed Or If Buffer Isn't Big Enough */ if(bytes_read == 0 || bytes_read == sizeof(buf)) return -1; /* Null Terminate Text */ buf[bytes_read] = '\0'; sscanf(buf, "%d", &s->boot_time); &s->t_days = s->boot_time/60/60/24; &s->t_hours = s->boot_time/60/60%24; &s->t_minutes = s->boot_time/60%60; &s->t_seconds = s->boot_time%60; }

我的结构看起来像这样：

typedef struct {

    /* Amount of Time Since Last Boot [dd:hh:mm:ss] */
    /* Time When System Was Last Booted */
    int boot_time;
    int t_days;
    int t_hours;
    int t_minutes;
    int t_seconds;

} sys_uptime_info;

我不喜欢使用int，因为它在这种情况下没有意义...我已经尝试过double和float但是当我这样做时，我无法从buf读取值到boot_time。非常感谢您的帮助！

Answer 1

这是你的问题

&s->t_days = s->boot_time/60/60/24;
&s->t_hours = s->boot_time/60/60%24;
&s->t_minutes = s->boot_time/60%60;
&s->t_seconds = s->boot_time%60;

更改为

s->t_days = s->boot_time/60/60/24;
s->t_hours = s->boot_time/60/60%24;
s->t_minutes = s->boot_time/60%60;
s->t_seconds = s->boot_time%60;

当你看到[error：“左值作为赋值的左操作数时需要左值]时，你要检查的第一件事是每个赋值的左边。一个左值应该总是解析为一个内存地址。变量名是lvalues并且可以比较对象.s-＆gt; t_days是一个左值，可以赋予一个与＆amp; s-＆gt; t_days不同的值。左边值被称为，因为它们可以出现在赋值的左侧.rvalues是值可以出现在右侧。在这种情况下，你在赋值运算符的左侧有一个右值。

将proc / uptime转换为DD：HH：MM：SS

1 个答案: