Use C to obtain CPU usage

# Include <stdio. h> <br/> # include <stdlib. h> <br/> # include <unistd. h> // header file <br/> struct occupy // declare an Occupy struct <br/> {<br/> char name [20]; // define a char array name with 20 elements <br/> unsigned int user; // define an unsigned int-type user <br/> unsigned int nice; // define an unsigned int-type nice <br/> unsigned INT system; // define an unsigned int-type system <br/> unsigned int idle; // define an unsigned int-type idle <br/> }; <br/> float g_cpu_used; // define a global Float Type g_cpu_used. <br/> int cpu_num; // define a global int type cup_num <br/> void cal_occupy (struct occupy *, struct occupy *); // declare that the non-typed function cal_occupy contains two struct parameters <br/> void get_occupy (struct occupy *); // declare that the untyped function get_occupy contains a struct parameter <br/> int main () // start the main function <br/>{< br/> struct occupy ocpu [10]; // define the Occupy struct variable name as ocpu containing 10 elements <br/> struct occupy ncpu [10]; // define the Occupy struct variable name as ncpu containing 10 elements <br/> int I; // define a local int variable I </P> <p> cpu_num = sysconf (_ SC _nprocessors_onln ); // The number of CPUs returned by the system call is assigned to cpu_num <br/> for (;) // endless loop <br/>{< br/> sleep (1 ); // wait 1 second <br/> get_occupy (ocpu); // call the get function to bring back the struct array for the first time <br/> sleep (1 ); // wait 1 second <br/> get_occupy (ncpu); // call the get function to bring back the struct array for the second time <br/> for (I = 0; I <cpu_num; I ++) // cyclically cpu_num-1 Times <br/>{< br/> cal_occupy (& ocpu [I], & ncpu [I]); // call the cal function to bring back the struct array <br/> printf ("CPU [% d] = % F/N", I, g_cpu_used ); // print the usage of g_cpu_used in 6 decimal places <br/>}< br/> void <br/> cal_occupy (struct occupy * o, struct occupy * n) // For a non-type cal function, the pointer variable O and N of the two struct types of the two parameters <br/>{< br/> double OD, nd; // define the Double Precision Real Variable OD, nd <br/> double ID, SD; // define the Double Precision Real Variable ID, SD <br/> double scale; // define the scale variable with Double Precision <br/> OD = (double) (o-> User + O-> nice + O-> system + O-> idle ); // The First Time (User + priority + system + idle) is assigned to OD <br/> Nd = (double) (N-> User + N-> nice + N-> system + N-> idle); // second (User + priority + system + idle) the time is then assigned to OD <br/> scale = 100.0/(float) (Nd-od); // 100 division by force conversion (Nd-od) the difference is that the float type is assigned to the scale variable <br/> id = (double) (N-> User-o-> User ); // The difference between the first time and the second time is assigned to the ID <br/> SD = (double) (N-> system-o-> system ); // The difference between the first and second time of the system is then assigned to SD <br/> g_cpu_used = (SD + id) * 100.0)/(Nd-od ); // (User + System) 100) Division (time difference between the first time and the second time) then assigned to g_cpu_used <br/>}< br/> void <br/> get_occupy (struct occupy * O) // For the non-type get function, the pointer o obtained by the class containing a form parameter struct <br/>{< br/> file * FD; // define the file pointer FD <br/> int N; // define the local variable N as the int type <br/> char buff [1024]; // define the local variable buff array as char type with a size of 1024 </P> <p> FD = fopen ("/proc/STAT", "R "); // open the stat file as R read and then assign it to the pointer FD <br/> fgets (buff, sizeof (buff), FD ); // read the string with the buff length from the FD file and save it to the buff space at the starting address <br/> for (n = 0; n <cpu_num; n ++) // cyclically cpu_num-1 Times <br/>{< br/> fgets (buff, sizeof (buff), FD ); // read the string whose length is buff from the FD file and save it to the buff space where the starting address is buff. <br/>/* The following describes how to convert the buff string to data based on the format parameter. the result is stored in the corresponding struct parameter */<br/> sscanf (buff, "% S % u", & O [N]. name, & O [N]. user, & O [N]. nice, & O [N]. system, & O [N]. idle); <br/>/* the output is incorrect */<br/> // fprintf (stderr, "% S % u/N", O [N]. name, O [N]. user, O [N]. nice, O [N]. system, O [N]. idle); <br/>}< br/> fclose (FD); // close the file FD <br/>}< br/>