i have ac program that runs following command:
system("sudo grep '' /sys/class/dmi/id/board_*")
and give output on command line.
I want the output to be stored in some variable in c program, so that i can filter board_serial
.
Take a look at popen . Here is a simple example of how you could use it to capture the program output:
#include<stdio.h>
int main()
{
FILE *p;
p = popen("ls -l", "r");
if(!p) {
fprintf(stderr, "Error opening pipe.\n");
return 1;
}
while(!feof(p)) {
printf("%c", fgetc(p));
}
if (pclose(p) == -1) {
fprintf(stderr," Error!\n");
return 1;
}
return 0;
}
But, it looks like you just want to read some value from a file, am I right? I would prefer to just open ( fopen()
) the files which have the values inside and read those values to variables in my C program. Try something like this (just a simple example):
#include<stdio.h>
#include<stdlib.h>
#define MAX 100
int main()
{
FILE *fp;
char result[MAX];
int i;
char c;
fp = fopen("/sys/class/dmi/id/board_name", "r");
if(!fp) {
fprintf(stderr, "Error opening file.\n");
return 1;
}
i = 0;
while((c = fgetc(fp)) != EOF) {
result[i] = c;
i++;
}
result[i] = '\0';
printf("%s", result);
i = atoi(result);
printf("%d", i);
if (fclose(fp) == -1) {
fprintf(stderr," Error closing file!\n");
return 1;
}
return 0;
}
Easiest way is to redirect the output to a file and the read that file for parsing the output.
system("sudo grep '' /sys/class/dmi/id/board_* 1>out.txt 2>err.txt");
fd_out = fopen("out.txt", "r");
fd_err = fopen("err.txt", "r");
Or you can use popen
function.
fd_out = popen("sudo grep '' /sys/class/dmi/id/board_*", "r");
Use dup or dup2 to duplicate standart output fd to a file fd
Yes popen is definitely the best choice. Have a look here
http://www.yolinux.com/TUTORIALS/ForkExecProcesses.html
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