fdclose.c

#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Take a PID and close all of the file descriptors */

int main(int argc, char **argv){
    FILE *fp;
    char* path;
    pid_t file_descriptor;
    char command[100] = "/usr/bin/lsof -p ";

    if ( !argv[1]) {
        printf("\nPlease enter a PID \n");
        return 0;
    }
    strcat(command, argv[1]);
    strcat(command,  " | /usr/bin/awk ' $8 ~ /^-?[0-9]+\\.?[0-9]*$/ {print $8} ' ");
    printf("Looking for file descriptors... \n");
    fp = popen(command, "r");

    if (fp == NULL) {
        printf("Failed to run command\n" );
        exit(1);
    } 
    while (fgets(path, sizeof(path), fp) != NULL) {
        file_descriptor = (pid_t) atoi(path);
        if (file_descriptor)
            if (close(file_descriptor))
                printf("\n Something wrong happened when trying to close this fd %d \n", file_descriptor);
            else
                printf("\n File descriptor closed successfully: %d \n", file_descriptor);
    }

    pclose(fp);
    return 0;
}