Get memory status under linux

Obtained through the proc file system

Under proc, there is proc / meminfo. This file will provide the corresponding memory usage at this moment.
Many upper-layer interface data sources of the system are also derived from this.

 cat /proc/meminfo 
MemTotal:       131921988 kB
MemFree:        90476752 kB
Buffers:          765764 kB
Cached:         13274276 kB
SwapCached:       131872 kB
Active:         27448120 kB
Inactive:        9399016 kB
Active(anon):   21696856 kB
Inactive(anon):  1133872 kB
....

Via sysinfo

In Linux, sysinfo is mainly used to obtain system-related information.                 

In Linux, sysinfo is a structure used to obtain system-related information.

Function declaration and prototype:

#include <sys/sysinfo.h>

int sysinfo(struct sysinfo *info);

main members.

struct sysinfo {                  
long uptime;            
/* 启动到现在经过的时间 */                  
unsigned long loads[3];  
/* 1, 5, and 15 minute load averages */                  
unsigned long totalram;  /* 总的可用的内存大小 */
unsigned long freeram;   /* 还未被使用的内存大小 */
unsigned long sharedram; /* 共享的存储器的大小 */
unsigned long bufferram; /* 缓冲区大小 */                  
unsigned long totalswap; /* 交换区大小 */                  
unsigned long freeswap;  /* 还可用的交换区大小 */
unsigned short procs;    /* 当前进程数目 */
char _f[22];         /* 64字节的补丁结构 */
....

You can use the memory status corresponding to this interface.

Reference example:

 size_t getFreeMemorySize()    
 {                      
   struct sysinfo memInfo;
   sysinfo(&memInfo);                     
   return memInfo.freeram/1024/1024;                                                                                                                                                                           
 }