/* 
 * access /proc entry for current process 
 */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>

void show_file(pid_t pid, char *simplename);

int main(void) {
    pid_t pid = getpid();
    show_file(pid, "cmdline");
    show_file(pid, "environ");
    show_file(pid, "limits");
    show_file(pid, "status");
    return 0;
}

void show_file(pid_t pid, char *simplename) {
    int namesz = snprintf(NULL, 0, "/proc/%d/%s", pid, simplename);
    char name[namesz+1];
    snprintf(name, namesz+1, "/proc/%d/%s", pid, simplename);
    printf("filename '%s'\n", name);
    errno=0;
    int infile = open(name, O_RDONLY);
    if (infile == -1) { 
        printf("open failed:  %s\n",strerror(errno));
    } else {
        char inchar;
        while (read(infile, &inchar, 1) > 0) {
            if (inchar == '\0') {
                putchar('\n');
            } else {
                putchar(inchar);
            }
        }
        putchar('\n');
    }
}