I am currently writing a program that will read the / proc / stat file and parse every line that will be stored as tokens, and then processed and displayed in the output table. I am at the stage when I managed to get the program to parse the program, but when it comes to storing tokens in different values of the array, I get an error: segmentation error (dropping the kernel). I'm not sure what causes this, since I already allocated memory. I also pretty start with C.
//standard input/output file to help with io operations #include<stdio.h> //standard library files to help with exit and other standard functions #include<stdlib.h> //header file for usleep function #include <unistd.h> #include <string.h> //header file for strtok function int main() { //FILE pointer will need to be declared initially, in this example the name is fp FILE *fp; //A character pointer that will store each line within the file; you will need to parse this line to extract useful information char *str = NULL; //size_t defined within C is a unsigned integer; you may need this for getline(..) function from stdio.h to allocate buffer dynamically size_t len = 0; //ssize_t is used to represent the sizes of blocks that can be read or written in a single operation through getline(..). It is similar to size_t, but must be a signed type. ssize_t read; float cpu_line1[4]; float cpu_line2[4]; float cpu_line3[4]; float cpu_line4[4]; float cpu_line5[4]; float page[2]; float swap[2]; float intr; float ctxt; float btime; //a variable declared to keep track of the number of times we read back the file unsigned int sample_count = 0; //opening the file in read mode; this file must be closed after you are done through fclose(..); note that explicit location of the file to ensure file can be found fp = fopen("/proc/stat", "r"); //checking if the file opening was successful; if not we do not want to proceed further and exit with failure code right away if(fp == NULL) { exit(EXIT_FAILURE); } int i = 0; char **string = NULL; //declaration of string string = (char**)malloc(10*sizeof(char*)); //assign space for 10 pointers to array for (i=0; i<10; i++) //allocate 50 bytes to each string in the array { string[i] = (char*)malloc(50*sizeof(char)); } char *s = NULL; //a loop that will read one line in the file at a time; str will read the line; len will store the length of the file while(1) { printf("\e[1;1H\e[2J"); //this line will make sure you have cleared the previous screen using C powerful format specifiers printf("----------------------------------------------------------------\n");//used for presentation printf("Sample: %u\n", sample_count); //showing the sample count int i = 0; //counter while ((read = getline(&str, &len, fp)) != -1) { // printf("Retrieved line: \n%sof length: %zu, allocated buffer: %u :\n", str, read, (unsigned int) len); s = strtok(str, " "); printf("Test program: %s\n", s); } if (i=0) { sprintf(string[0], s); cpu_line1[0] = atoi(strtok(NULL, " ")); cpu_line1[1] = atoi(strtok(NULL, " ")); cpu_line1[2] = atoi(strtok(NULL, " ")); cpu_line1[3] = atoi(strtok(NULL, " ")); } if (i=1) { sprintf(string[1], s); cpu_line2[0] = atoi(strtok(NULL, " ")); cpu_line2[1] = atoi(strtok(NULL, " ")); cpu_line2[2] = atoi(strtok(NULL, " ")); cpu_line2[3] = atoi(strtok(NULL, " ")); } if (i=2) { sprintf(string[2], s); cpu_line3[0] = atoi(strtok(NULL, " ")); cpu_line3[1] = atoi(strtok(NULL, " ")); cpu_line3[2] = atoi(strtok(NULL, " ")); cpu_line3[3] = atoi(strtok(NULL, " ")); } if (i=3) { sprintf(string[3], s); cpu_line4[0] = atoi(strtok(NULL, " ")); cpu_line4[1] = atoi(strtok(NULL, " ")); cpu_line4[2] = atoi(strtok(NULL, " ")); cpu_line4[3] = atoi(strtok(NULL, " ")); } if (i=4) { sprintf(string[4], s); cpu_line5[0] = atoi(strtok(NULL, " ")); cpu_line5[1] = atoi(strtok(NULL, " ")); cpu_line5[2] = atoi(strtok(NULL, " ")); cpu_line5[3] = atoi(strtok(NULL, " ")); } if(i=5) { sprintf(string[5], s); page[0] = atoi(strtok(NULL, " ")); page[1] = atoi(strtok(NULL, " ")); } if(i=6) { sprintf(string[6], s); swap[0] = atoi(strtok(NULL, " ")); swap[1] = atoi(strtok(NULL, " ")); } if(i=7) { sprintf(string[7], s); intr = atoi(strtok(NULL, " ")); } if(i=8) { sprintf(string[8], s); ctxt = atoi(strtok(NULL, " ")); } if(i=9) { sprintf(string[9], s); btime = atoi(strtok(NULL, " ")); } printf("----------------------------------------------------------------\n"); //used for presentation usleep(500000);//this will ensure time delay rewind(fp);//rewind the file pointer to start reading from the beginning sample_count++;//update the sample count } //Frees pointers to make program memory efficient free(str); for (i=0; i <10; i++) { free(string[i]); } //once you are done, you should also close all file pointers to make your program memory efficient fclose(fp); return 0;
}
EDIT Here is a copy of what the program looks like when you run it in Cygwin
Example: 0
Testing Program: cpu
Test Program: cpu0
Test Program: cpu1
Test Program: cpu2
Test Program: cpu3
Testing program: page
Testing program: swap
Test program: intr
Test Program: ctxt
Test Program: btime
Segmentation error (kernel flushing)